Sciencemadness Discussion Board

Electroforming is useful...

BromicAcid - 9-5-2004 at 17:49

Electroforming is kind of like a beefed up version of electroplating. The difference being that the coating of metal deposited is significantly greater then those coating achieved with electroplating.

Examples of useful electroforming to the mad scientist fall almost exclusively into apparatus manufacture. You could carve a retort out of wax then paint it with electrically conductive paint (although some sources said a dusting of graphite could suffice) then coat that with silver and follow it up with melting out the wax and viola, a silver retort. You could take a metal pipe endcap and electroform a layer of nickel on it, then pour some HCl into it and dissolve out the iron and be left with a nickel crucible.

However from what I've read this process is very fickle and can be thrown off by variances in current of less then .2 A and that the coatings can easily be stressed. I've read that the stress can be relieved by reversing the polarity and dissolving the cathode you are trying to build up then reversing again and redepositing. Also I've read that the baths for electroforming are very similar to electroplating.

So what I'm getting to is, electroforming is useful and does anyone have any real world experience with it. We're not jewelers here, we do not need that perfect finished surface, we just need a crucible or other vessel that will not crumble and will hold together. So what kind of power supply would suffice and what kind of results should one expect from an at home operation. I've found kits to do this but as usual they are beyond a humble mad scientist's budget.

Tacho - 10-5-2004 at 03:52

I did a small Garfield face (aprox 2x2cm) some years ago. It was after many failed tries. I remember that this one was left for something like a few days under very small current, in acidic copper sulfate solution. In the end, the front surface (in contact with the conductive surface) was perfect and beautiful, but the back was very irregular, covered with warts and lumps, but it was quite solid and resistant.

The problem, to me, seems to be the conductive paint. The result above was achieved using some plastic dissolved in acetone and mixed with powdered graphite. To make the distribution of current more homogeneous, after the first layer of paint, I put some thin copper wires making a mesh, and then another layer of paint. The existent conductive silver paints (find them at the local electronics hobby shop) are quite expansive.

I painted on a RTV silicone rubber “positive” mold, to be able to detach it and have a detailed “negative” conductive mold I could electroplate on.

Recently I found out that rubber latex (a white goo, I found mine at a fiberglass supply shop), mixed with graphite, after dry, makes a good conductive rubber. But my results with electroplating it were frustrating. But then again, ALL my experiments with electroplating are frustrating, so, if you can already do decent electroplating...

I think the trick to decent electroplating is using cyanide salts, but I don’t want to buy that (dangerous), unless I’m sure it works.

Have you heard of electroless nickel plating? Take a look at the Hotblack thread at the Miscellaneous forum.


Edit: Many sources say that all you have to do is "paint" the mold with powdered graphite to render it conductive. And they mention it as a trivial thing. Well, I wish luck to those who try. And please, post how you did it, because I could never make it work.

I always used the same powdered graphite I bought years ago, maybe is not the proper one.

[Edited on 10-5-2004 by Tacho]

Saerynide - 10-5-2004 at 07:51

How is the powered graphite supposed to stick to the mold if you're gonna dunk it into a solution?

Tacho - 10-5-2004 at 07:53

Quote:
Originally posted by Saerynide
How is the powered graphite supposed to stick to the mold if you're gonna dunk it into a solution?


Exactly!

Saerynide - 10-5-2004 at 08:38

Strange :o I guess it might be possible if it was one of those rubbery/jelly-like molds that stick to any dust/particles it touches and wont let go of them even when dunked in soapy water. Like the material they use to make those sticky lizards kids throw against walls and they get stuck?

axehandle - 10-5-2004 at 09:01

Hmm. This has some relevance to one of my projects. I was thinking latex goo (the same that's used when making dildos) mixed with graphite.

chemoleo - 10-5-2004 at 09:20

The best one I found for moldmaking is alginate, and gypsum/plaster of paris.
Latex didnt work well at all, i.e. it takes forever to dry, and it becomes milky white if exposed to water for a bit... alginate is happy in water, though. It doesn't redissolve, plus I am sure it is conductive (consisting 80+ % of H2O).

PS don't u mean condoms? There's a difference :D

Tacho - 10-5-2004 at 09:55

I mixed latex goo with graphite to make a pressure-sensitive rubber. The idea was that it's electrical resistance would lower under pressure. It does, but very irregularly.

A thin layer of my latex goo takes only a couple of hours to dry, but you have to paint many thin layers to have a resistent mold.

Salty alginate with graphite may prove to be good but, as I said, one must first be able to do decent electroplating.

Does anybody know a foolproof method for decent electroplating? Any metal will do!

Organikum - 10-5-2004 at 13:19

These coating methods sound incredible complicated to me.

I would suggest to get some zinc-spray, 99% zinc, at every automobile supply shop and to spray whats to plate. Bronze spray, aluminium spray, I have even seen plain copper spray with 98% copper there.

Or do I overlook something here?

I remember I have read that cavities are a big probelem with this technique, which can be overcome by certain organic additives which cause a equal deposition of the metal also in caves and in thicker layers. Forgot the name though, but can look it up if needed.

http://www.finishing.com
(the link is from memory and unchecked)

axehandle - 10-5-2004 at 13:34

If you find silver spray, contact me. I'm trying to make a very glittery piece of jewellry for my GF, based on Ti.

/A

BromicAcid - 10-5-2004 at 13:45

Quote:

Have you heard of electroless nickel plating? Take a look at the Hotblack thread at the Miscellaneous forum.


Yes, electroless nickel plating is good but the entire reason I wanted to do this electroforming was to make a silver retort for anhydrous hydrazine production.

axehandle - 10-5-2004 at 14:11

Silver is (comparatively) cheap. And very malleable. Why not cast it?

BromicAcid - 10-5-2004 at 14:37

Quote:

Silver is (comparatively) cheap. And very malleable. Why not cast it?


Also quite feasible, hence my U2U conversations with you, but if I had found a simple setup for electroforming the sciencemadness way that would have been more enticing. Regardless, I'm in no hurry, it would be mostly for bragging rights anyways. :D

axehandle - 10-5-2004 at 15:18

I see. Well, electroplating is more entizing. Contact a jeweller's supplier and buy some silver cyanide. It works, but I'm afraid you'll need a Pt or at least a platinized anode.

/A

BromicAcid - 10-5-2004 at 15:28

I thought that I could use a fine silver anode and that would replenish the solution as it took up the silver cations.

axehandle - 10-5-2004 at 15:33

Probably. But it will be a very thin layer of Ag.

Tacho - 11-5-2004 at 03:28

Organikum,

Are you talking about spray paints (cans) or the pure metal spray, done with a special high temperature gun? Most paints do not render conductive surfaces, although, thinking about it, the zinc ones that claim something like “cold galvanizing” may worth a try, after all, galvanic protection requires electrons moving from here to there.

Edit: You said somewhere that you were electrolyzing ZnCl and getting Zn metal. How does that metal deposit? Clean and shiny?

Axehandle,

You said the magic word: cyanide. Has anybody tried cyanide salt plating? I have a feeling that’s the easy way to go. But, cyanide is very poisonous, releases very poisonous gas in acidic solution and so on...

Bromic acid,

I don’t know what's hydrazine, but if it requires pure silver, remember that's very hard to find. I’ve dissolved silver in nitric acid many times, and the solution is always very blue, due to copper. To obtain pure silver, one way is to precipitate the silver chloride with table salt and reduce using... using... eh...

I would start with molten NaOH (you know about that, don’t you?), or mix it with fine carbon then blowtorch it in a crucible. I’ve precipitated the chloride (that's easy), but never reduced it.

[Edited on 11-5-2004 by Tacho]

Saerynide - 11-5-2004 at 05:00

Can you dissolve the silver in nitric acid to get silver nitrate, then stick a copper wire in to reduce the silver ions while creating copper nitrate?

Tacho - 11-5-2004 at 05:51

You can but, in my experiences, the silver deposit is in the form of a very fine loose black powder. In fact, looks like a black ink, mixing in the solution. It didn't even decant overnight. Colloidal silver?

Eventually the copper ions will start reducing too if you don't use separate cells.

Saerynide - 11-5-2004 at 05:55

Really? When we did it at school, we got silver crystals that were very shiny and beautiful :o

vulture - 11-5-2004 at 05:57

AgNO3 forms an electric doublelayer with insoluble silver salts, keeping them in suspension. Maybe the same thing happens with Ag?

A large excess of indifferent electrolyte (KNO3, KCl, NaCl, etc) will fix this.

Marvin - 11-5-2004 at 06:59

Bromic,

The silver mirror reaction I mentioned for coating the inside of glassware to protect from hydrazine attack (speculation this would work well), would also work for producing a conductive coating on a non conductive former for producing silver containers. The surfaces need to be totally free of greese to adhere. Watshed with dilute NaOH and scrubbed. I dont see how for the actual electroforming youd be able to avoid cyanide for a decent plate though. When I did silver plating it was an everything in fume hood plus a great deal of paranoia job.

If you are willing to keep the current density very very low, something might be possible (eventually) with just silver nitrate, but it wont be good mechanically.

Tacho - 11-5-2004 at 09:14

Sorry Saerynide,

I realize now that we are talking about two different things: you are talking about getting pure silver by reducing it with copper in the silver nitrate solution. I've never done that but I've heard it is a common chemical demonstration.

I was talking about electroplating silver from silver nitrate solution. I used graphite electrodes, just to test the principle.

BromicAcid - 11-5-2004 at 14:05

Quote:

I don’t know what's hydrazine, but if it requires pure silver, remember that's very hard to find. I’ve dissolved silver in nitric acid many times, and the solution is always very blue, due to copper. To obtain pure silver, one way is to precipitate the silver chloride with table salt and reduce using... using... eh...


I can buy silver ignot at my local jewlers shop for very near market value so fairly easy for mt to aqure. The problem with making anyhydrous hydrazine that the silver poses the sole solution to is the distillation with a 3x stoichiomentric amount of NaOH or KOH. This mix eats glassware more then usual and if the retort is made of some metal other then silver it easily catalyzes the explosive decomposition of the hydrazine thus formed.

Saerynide - 12-5-2004 at 00:14

Oh, I thought you wanted to get pure silver for hydrazine production because the kind you buy isnt pure enough, so I was proposing a way to make pure silver :P

There is hope without cyanide!

Tacho - 14-5-2004 at 03:28

Our wise, alert and intelligent administrator mentions a large excess of KNO3, KCl or NaCl in the solution as a way to deposit silver. A quick search in the usenet groups showed a recipe for cyanide-less silver plating: 3,2g AgNO3, 64g KI and 6 drops of concentrated H2SO4 in 200ml of water.

I decided to do a test using a little bit of AgNO3 in a strong solution of NaCl, and guess what? No, I did not get a shiny layer of solid silver, but my graphite electrode was covered with a light gray silver coat. It could be wiped away with a paper towel, but I believe it’s a matter of current density and improved formula.

I used a very large current, and the smell of chlorine was an annoying problem. I think that’s why the formula above uses expensive KI, you don’t get noxious chlorine, just iodine. Bromine salts may be an intermediate solution.

People also mention that decent copper plating can be achieved using copper sulfate and organics like table sugar. I didn’t notice if they mentioned some H2SO4.

axehandle - 14-5-2004 at 05:13

I've seen cyanideless electroplating solution in my jewellers supplier's catalog. It existed for both gold and silver. The comp wasn't specified though.

Still, I'd just cast the retort... Ag is only about 3 times(?) as expensive as Ti.

Edit: <b> Hey, why not take a plain copper retort to a jeweller and have him electroplate it?</b> That shouldn't be too expensive. The machines I've seen for electroplating are big, expensive and complicated. I doubt a good result could be obtained using homebuilt machinery.


[Edited on 2004-5-14 by axehandle]

Tacho - 14-5-2004 at 05:56

axehandle,

Those are certainly good solutions. But the thing is: electroforming IS (really) useful! Bromic started this thread thinking of a specific task, but if we could establish a foolproof way to basic electroforming, I believe we will be accomplishing a great task for our collective.

axehandle - 14-5-2004 at 06:15

Tacho, you're right. I plead stupidity. I'm on morphine right now so I'm not 100% clear in the head.

Tacho - 15-5-2004 at 06:57

As I added AgNO3 solution to NaBr solution, the obvious thing happened: AgBr precipitated!

Duh...

I saw no AgCl precipitate in the NaCl solution, although it should have been there! And that deposit on the graphite had to be silver, it sure was not sodium!

I made a pretty good smooth, solid deposit of copper on graphite using a weak solution of CuSO4 in 50 ml of water, a tablespoon of sugar, ten drops of 30% sulfuric acid and 2,5V. It took about one hour do it. The CuSO4 solution was light blue, like a swiming pool. Sorry, didn't weight anything. If the sugar had anything to do with the smoothness, is yet to be determined.

Edit: distance between eletrodes: aprox. 2 cm. No currents were measured.

Copper seems by far the easiest metal do do eletroforming, but I won't give up on silver.



[Edited on 15-5-2004 by Tacho]

axehandle - 15-5-2004 at 07:47

Quote:

Copper seems by far the easiest metal do do eletroforming, but I won't give up on silver.

The price and complexity of the machines I've seen for Au/Ag plating suggest that it's a very delicate process. :(

Saerynide - 15-5-2004 at 08:26

Whats the sugar for? :D

Tacho - 15-5-2004 at 10:58

Quote:
Originally posted by Saerynide
Whats the sugar for? :D


I have no clue. Information on the net also mention dextrose, gelatin, syrup etc.

I don't know if it's the sugar, but is the best plating I've ever done!

axehandle, you are right. Silver sucks! I give up.

The Electroplater's Handbook

Cyrus - 15-5-2004 at 12:28

For bright copper plating here is a
formula.

No. 3 Bright Copper Bath

30 oz CuSO4
9 oz H2SO4
1 gal dH20
a smidgeon of (NH2)2CS- thiocarbamide/thiourea.
voltage 2-5 volts

The author says to do a test plate,add tiny amounts of thiourea -0.005 oz, then check if the plate is dull, if so, add some more thiourea.

The book seems pretty reliable and he has many electroplating and electroforming formulas for copper, tin, silver, gold, and
even lead- for silverware. :P
The book also has immersion plating formulas for zinc and all of the above metals except lead, including a bath with
AgNO3 and NaCl. I thought he was crazy
until the post that said that AgCl did not precipitate? Why not? That bath also had
cream of tartar in it, what would that do?
Is anyone interested in more info?

For making nonconductive surfaces conduct, I have tried graphite powder from a lock lubricant mixed with xylene and polystyrene, but the powder particles seem too big, and don't conduct. Where do I get finer graphite? Its not like you can grind it up in a mortar and pestle!

Cyrus - 15-5-2004 at 12:41

Quote:
Originally posted by Saerynide
Whats the sugar for? :D


Its supposed to be a brightener, correct me if I'm wrong, but this is how I believe it works. On the object you are electroplating there are small bumps, and when voltage is applied, corona leakage -is this the right phrase? comes off of these bumps, so that the metal ions in solution are more attracted to the bumps,
and thus deposit there, making the bumps larger, ad infinitum. Eventually on a small scale your object looks like it's covered in grass- which is very dull and is a weak coating. To prevent this, we add
brighteners, which have a certain (partial)? charge, and are attracted to the bumps and stick onto them, forcing the metal ions to go to the recesses and fill those up first. This creates a nice smooth
finish and is SHINY! I love shiny things.
In my recipe, thiourea is the brightener.

Tacho - 16-5-2004 at 04:58

Thank you Cyrus, I’ll try to find or make thiourea.

I did many test baths for copper plating and found out a few things:

1-Sugar does make a difference. In two equal baths, one with sugar, the other without, the plating with sugar holds better, is more solid and better looking. I haven’t tested anything but sugar as an additive.

2- The worse baths were the ones with too much H2SO4, pH<4. In fact, I believe that has been the major problem with my plating experiments until today. I found out that acid IS necessary, but in minimum amounts. pH around 5 is excelent. In very acidic baths the deposit is powdery and loose. Is that more related to current than acidity itself? I have no idea!

3- Voltage has to be kept below 3V. Is that more related to current than voltage itself? I have no idea! Above 3 V the deposit is dark and powdery.

The recipe that gave me best results until now: 10g CuSO4, 30g white sugar, 300ml water and just enough H2SO4 to bring pH to 5. Sorry, the H2SO4 I was using was of unknown concentration, a leftover, so I have no measures, but be sure that is just a bit, and too much will spoil your bath. The electrodes were graphite leads (diameter 2mm), imersed about 3 cm in the bath, parallel, 2cm apart, 2,5 V. Current for this setup 10mA. Change in color in 1 minute, good covering in 15 minutes.

Tacho - 16-5-2004 at 15:21

I think I figured the H2SO4 thing! When you have to plate large surfaces, you need to conduct a lot of current, hence the large amount of acid in the recipes.

So, I presume that the proportion of acid has to be smaller for small plating surfaces, to prevent excessive current density.

It's either that or something else!

And my initial tests with alginate+graphite are NOT very good. I don't think it will work at all.

Cyrus - 16-5-2004 at 16:29

The thiourea can be bought online cheaply as taste test strips, but I do not know how much there is in the strips.

If you can't get thiourea, use urea, which is the same except for a sulfur replacing an oxygen atom. I doubt urea works as
well though.

With the dull and crumbly deposits, there is too much current density/voltage, and perhaps too much acid. The acid is not added to increase conductivity, though.
It replentishes the bath so it can be used indefinitely, dissolving the anode to make more CuSO4, but you have to use a copper anode. I need to check up on the formulas
though.

Why don't you try plating on a substrate other than graphite, because nothing will
adhere that well to graphite- the graphite
will shear off of itself and come away with the copper when you test it for adhesion.

Tacho - 17-5-2004 at 03:36

Quote:
Originally posted by Cyrus
(snip)

Why don't you try plating on a substrate other than graphite, because nothing will
adhere that well to graphite- the graphite
will shear off of itself and come away with the copper when you test it for adhesion.


Graphite is used widely to make conductive surfaces from non-conducting ones. I just have not found the right way yet. Besides, I may be expecting it to detach from the copper layer easily if it is just a mold.

Silver mirror deposit is good only for glass-like surfaces, and electroforming on a mold will require something that can be detached, melted or dissolved away, like some rubber, paraffin, plastic, gypsum or carbonates.

Somewhere in my fading memories, I see a silver salt being reacted with sulphur-containing gas to create a conductive silver sulphite layer. But I can't connect the right neurons and this could be just my imagination.

Edit: About the H2SO4, I remember it cleans oxidized copper, so it may improve the deposit by “keeping the layer clean”. I believe, however, that copper ions will form in the anode with or without the acid.

[Edited on 17-5-2004 by Tacho]

Ah-ha! I knew it!

Tacho - 17-5-2004 at 06:07

I found this in the usenet:


*********************************
From: Zoltan Nagy (nagy@cmt.anl.gov)
Subject: messages from eletqm-l
View: Complete Thread (30 articles)
Original Format
Newsgroups: sci.chem.electrochem
Date: 1998/05/26


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The following messages are copied from the e-mail list ELETQM-L. If you wish
to respond, POST a message on SCI.CHEM.ELECTROCHEM. (Please do not use
REPLY/MAIL, as your message will probably be lost. If you want to use mail,
make sure that you use the address of the appropriate message.) All messages
posted on SCI.CHEM.ELECTROCHEM are regularly mailed to ELETQM-L (and vice
versa).

*******************************************************************************

From: SMTP%"mac@encomix.es" 15-MAY-1998 11:44:38.91
To: NAGY
CC:
Subj: Re:

Message-Id: <3.0.1.32.19980516184120.007ac100@encomix.es>
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Date: Sat, 16 May 1998 18:41:20 +0200
To: eletqm-l@ufu.br
From: Manuel Algora <mac@encomix.es>
Subject: Re:
In-Reply-To: <19980514232307.28464.rocketmail@send1b.yahoomail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"

At 16:23 14/05/98 -0700, you wrote:
>
>Does anyone know how to make a good capacitor out of materials around
>the house? Thanks.
>

As long as you may have 2 conducting surfaces and an insulator in between,
you have made a capacitor. For instance, you may use two aluminium foils,
to be put in the outside and inside walls, respectively, of a plastic or
glass container, or a glass sheet. If you use a glass jar, then that's a
Leyden jar. You can also make use of electroplating. The following
procedure comes from the book "Secrets of Building Electrostatic Lightning
Bolt Generators", by Walt Noon (Lindsay Publications, Inc.) First you need
to make the surfaces of the jar conductive, so as to turn them in
electroplating electrodes.

1) Paint the outside of the jar with shellac or any other resin. Let it dry
completely.

2) Paint with (or dip into) a solution of silver nitrate in 50% alcohol.

3) While still wet, suspend the jar inside a larger jar or vessel, and put
some iron pyrite or potassium sulfite in the bottom of this larger jar,
which you then fill with sulphuric acid diluted with 8 parts of water.
Close this "reaction vessel", and hydrogen sulfide phumes shall develop,
which shall turn the silver nitrate coating into silver sulphide. Now you
have a conductive coating on the surface of your to-be Leyden jar.

4) To electroplate this surface, use a solution of copper sulphate in
diluted sulphuric acid, and put you jar inside this solution.

5) Attach the negative of a battery to the conducting surface of the jar.

6) As the anode, use a copper sheet, to be attached to the positive pole of
your battery. The outside of the jar shall be coated with copper.

7) Repeat as per the inside of the jar.

******************************


Isn't hydrogen sulphide that horrible poison that numbs your sense of smell than kills you and has no antidote?

Then I suggest the plating with cyanide!

Just kidding, don't do that!


Edit: How toxic is thiourea by the way?



[Edited on 17-5-2004 by Tacho]

Cyrus - 17-5-2004 at 15:46

Yep, H2S, thats the stuff, Threshold Limit Value of 14 mg/m^3. This the exact method The Electroplater's Handbook suggested.

Thiourea isn't extremely toxic, after all you put the test strips in people's mouths to see if they can taste it.

According to Flinn Scientific, it is a "Possible carcinogen; highly toxic; mild body tissue irritant. LD50 125 mg/kg"
You need a fraction of a gram, so I would be more concerned about the CuSO4,
H2SO4 and H2 gas generated;)

For making silver coatings on anything, I suggest the following method. It is not as adherent as electroplating of course, or they would all use this formula, but it may work for hydrazine.


12-3

Tollen's Test for Aldehydes and Ketones

(a.k.a. The Silver Mirror)



Reference: General Chemistry 4th edition by Darrell D. Ebbing, p 1041.



Description: Tollen's Reagent is added to two flasks. A dextrose water solution is added to one and swirled. The contents of the flask turn brown and then silver is plated onto the inside of the flask. Sucrose is added to the other flask. The contents may turn brown but no silver is plated.

Concept: Silver (I) is reduced to silver metal by aldehydes but not by ketones.





Materials:

· Gloves

· Goggles

· Two 500 mL Florence Boiling Flasks with rubber stoppers

· Nitric Acid

· Distilled water

· 200 mL 0.1 M Silver Nitrate

· Concentrated Ammonium Hydroxide

· 100 mL 0.80 M Potassium Hydroxide

· 100 mL 0.25 M Dextrose

· 100 mL 0.25 M Sucrose

· 100 mL Graduated Cylinders

· Pasteur Pipettes



Safety:

Nitric acid will burn skin terribly. Wear gloves and goggles.

Acetone is volatile. Do not use near flame. Work in hood when washing flasks with acetone.

Silver is toxic. Wear gloves and goggles.

Wash hands when done handling these chemicals.

Beware: I have heard that silver-ammonia mixtures, if left sitting around can become explosive.



Procedure:

Before Class:

Prepare the Flasks

Rinse the flasks with distilled water, leaving the water in the flask.

Using a pipette rinse the inside of the flask with Nitric acid and then swirl the acid and water in the flask.

Dump the contents of the flask into the beaker.

Rinse the flask with distilled water and dump this water into the beaker.

Using a pipette rinse the sides of the flask with acetone and then swirl the acetone in the flask.

Pour this small amount of acetone down the drain with the water running.

Rinse the flask once more with distilled water.



To both flasks:

Add 75 mL of 0.1 M Silver Nitrate

Pour small amounts of Ammonium Hydroxide to the silver and swirl until the solution is a brown color (muddy).

Pour small amounts of Ammonium Hydroxide to this muddy mixture until it becomes colorless, clear again.

Add 40 mL of Potassium Hydroxide and the solution will become muddy again.

Add Ammonium Hydroxide until the solution becomes colorless, clear again.



In Class:

To one flask add 100 mL of Dextrose. To the other add 100 mL of sucrose

Stopper both flasks.

Swirl the flasks so that the silver will plate more uniformly over the insides of the flasks (the plating will occur in the flask with dextrose within a few minutes).

Add a scoop of Dextrose to the flask with the sucrose swirl to silver plate it also.



An acrylic spray is available to coat the inside of the flask, to prevent the silver from tarnishing.



Clean-Up:

The contents of the flask that did not contain Methyl Ethyl Ketone can be washed down the drain. The contents of the flask that did contain ketone should be put into a waste bottle and taken to EH&S collection site as flammable hazardous waste.

Beware: I have heard that silver-ammonia mixtures, if left sitting around can become explosive.

- (Yep, they make silver fulminate,which may be a bonus for some:P)

Edit: please don't ask me for the formula.
I have no clue.



Notes: This demo is commonly called the Silver Mirror and is done at the Chemistry Open House Magic Show on a larger scale.

Has been used in C102.

[Edited on 17-5-2004 by Cyrus]

Tacho - 18-5-2004 at 03:29

Very straightforward! A good place to learn more about silvering mirrors is amateur telescope making sites. But I doubt any method can be simpler than the one you posted, although I believe the cleaning can be done using other acids. Nitric acid seems too precious for most in this forum. Water seems to wet my glassware fine after I put conc. H2SO4 in them, no grease seems to be left.

Common urea is NOT good as a brightening agent, I tried it. I’ll find and test thiourea.

I can’t get the H2S thing out of my head. It seems to be THE way to go to make conductive surfaces out of gypsum, wood and, hopefully, paraffin. I would appreciate if you could post any additional information you find on the subject.

My goal is to deposit a solid layer of metal on a paraffin mold. I think that would be a very useful trick.

Edit: By the way, your recipe mentions a "smidgeon" of thiourea. Sorry, but how much do you think that would be?

Edit2: A copper electroformed piece can easily be covered with tin or silver, both by imersion in fused metal or by means of simple-to-make electroless solutions. Maybe both. First chemically cover with thin silver, than carefully melt silver to wet the surface with skill and a blowtorch.

Edit3: Just bought 250g or reagent grade thiourea for the equivalent of U$8 or 6 euros. Seems that it's a common chemical, widely available. I will test it tonight.





[Edited on 18-5-2004 by Tacho]

[Edited on 18-5-2004 by Tacho]

[Edited on 18-5-2004 by Tacho]

Cyrus - 18-5-2004 at 15:43

Quote:
Originally posted by Tacho

Common urea is NOT good as a brightening agent, I tried it. I’ll find and test thiourea.



How much did you try? I would bet you added too much- next time just try a smidgeon!

Quote:
Originally posted by Tacho

Edit: By the way, your recipe mentions a "smidgeon" of thiourea. Sorry, but how much do you think that would be?



No, I don't like the units he uses either, but if I remember right, a smidgeon is the amount of powder that will cover about one fourth of a square inch, maybe it was a square centimeter, either way, you just feel your way until the plate is shiny.

Quote:
Originally posted by Tacho

Edit2: A copper electroformed piece can easily be covered with tin or silver, both by imersion in fused metal or by means of simple-to-make electroless solutions.



I've got a formula on this too.

1 oz/gal AgNO3
14 oz/gal Na2S2O3
10 oz/gal NH3 (Is it household strength ammonia or pure ammonia?!- probably household. Elsewhere you are supposed to add enough to make the silver precipitate Ag2S2O3? that forms dissolve.)

Just dip the copper object in.

I do not have any more info on the H2S method, but you also can make a copper or brass mold, and dip the mold in a solution of potassium sulfide - liver of sulfur, until the mold darkens, and plate on this. The plated metal is supposed to
peel right off. I can check the book out again to get more info.

Tacho - 19-5-2004 at 03:31

You are right about using too much urea, because I had the same results with thiourea. I’m sure thiourea is the right thing because, now that you mentioned it (thanks!) any search in the net (+plating +copper +thiourea) gives many serious results. I guess, as you said, I’ll have to feel my way until is shiny.

Just for the record, I used about 2g of urea for a 50ml bath and 0,1g of thiourea for the same volume. Thiourea turned the bath milky, showing it was way too much.

I tested a method to produce H2S that seems to be the safest, cleanest and... well, the best. I mixed paraffin with sulfur in a test tube (10:1 rate), heating with a burner caused the bubbling of a gas that turns silver brown. Caveat: careful with the heating, for some reason, everything started boiling suddenly, causing the paraffin to splatter all over.

Thanks for the silver thing.

A tin electroless plating solution would be stannous chloride and thiourea. There are recipes in the usenet. I will try it soon, but I'll make my own stannous chloride somehow. Its quite expensive here.

Edit1: This production of H2S with sulfur and paraffin is puzzling.Where does the hydrogens come from? Is the sulfur creating double bonds in the hydrocarbons? Could it be that I’m making just sulfur vapors? Would these tarnish silver?

[Edited on 19-5-2004 by Tacho]

Cyrus - 19-5-2004 at 15:10

I think sulfur would tarnish silver, but do not know what the reaction you are doing is.

Maybe you could try FeS + 2HCl -> H2S + FeCl2 or something similar with a sulfide.

The_Davster - 20-5-2004 at 15:54

Quote:
Originally posted by Tacho

I will try it soon, but I'll make my own stannous chloride somehow. Its quite expensive here.


[Edited on 19-5-2004 by Tacho]


Heres my little route to stannous chloride-all OTC
Electrolyise(I used 2A@12V) a saturated NaCl solution with solder electrodes(60%Sn 40%Pb), tin is preferentially oxidized and if any lead gets into the solution is is immediatly plated out. Add HCl to the resulting dirty solution, it is black/brown before acid addition. Filter. You now have a solution of sodium chloride and stannous chloride. Precipitate tin(II) carbonate by addition of baking soda. Filter again. Add just enough HCl to the stannous carbonate in a beaker to dissolve it all. Let it evaporate. I managed to get a nice pile(5-10g) of nice colorless crystalls, after only about 30min of electrolysis(plus the rest of procedure) but when I attempted a larger batch the solution turned piss yellow while evaporating for some reason.

Tacho - 21-5-2004 at 04:14

Thanks rogue chemist, I’ll try that!

I’m trying to make a conductive paint. One of my options is use precipitated reduced silver with some kind of binder.

To precipitate silver from silver nitrate solution, I’m currently testing 4 methods to see which gives the best paint:

1- Hydroquinone – slowly darkens and the precipitate seems grey. Funny, I thought hydroquinone would precipitate all silver at once.

2- Table sugar – Nothing happened in the first hour... Wait... I should have used dextrose, not sucrose!

3- Copper wire – I did this to finally see the famous “silver crystal tree”. To my luck, the silver tree is not beautiful at all, seems to made of a gray powder that, hopefully, will make a good paint. Its lack of beauty is probably due to tap water ions.

4- Two graphite electrodes and 6 volts – Very black ink-like solution. And guess what? Two mirror spots in the glass! If the tube was very clean, I guess I would have mirrored (sp?) it completely!


Edit: any idea for a binder will be apreciated. Most binders I used with graphite make it non-conductive.

I'm thinking of gelatin. After dry, I would bath it in formalin, to make it insoluble.

Or very diluted rubber latex.

IMPORTANT EDIT: The solutions posted above have ethanol. I estimate about 50%

[Edited on 21-5-2004 by Tacho]

[Edited on 22-5-2004 by Tacho]

Cyrus - 21-5-2004 at 20:41

If you go to www.pupman.com there are several threads on electroplating on nonconductors.

They suggest using graphite and styrene dissolved in an organic solvent (I believe tolulene.) I tried this, but my graphite particles are disgustingly large. :mad:

The fine silver idea sounds great,
conductive silver epoxies are made with colloidal silver, try mixing the silver sludge with a little epoxy.

I might try this, except I am making a Vandegraaff generator, and for the sphere, which is more than 1000 in^2. (large I know) this might take a lot of silver. I first want to electroplate the conductive layer with copper, and then immersion plate it with silver.

Tacho - 22-5-2004 at 06:16

After 24 hours:
1- Hydroquinone – A grey precipitate. Silver powder, too coarse to be black, but good enough to paint. Interesting, though, is the fact that the liquid left after precipitation had this beautiful golden color. COLLOIDAL SILVER?
2- Table sugar – Nothing happened in the first hour... Nothing happened in the 24 hours after.
3- Copper wire – Probably my silver tree was ugly because I had ethanol in the solution. It was a great disappointment to find out that the “tree” had this kind of “coagulating” behavior, resulting in chunky pieces of soft silver.
4- Two graphite electrodes and 6 volts – Good black fine powder. I just could not test it for conductivity yet.

About the binder: Epoxy and linen seed oil are options, but I face practical problems in mixing water-wet fine powder with non-polar (oil like) solvents.

About H2S: The paraffin-sulfur thing, if produces any H2S at all, it’s nothing compared to FeS+HCl. The gas produced by this mix makes the AgNO3-covered piece of wood instantly very dark. In the other hand, much more danger is involved. Remember: WORSE THAN CYANIDE GAS. FeS is easily made heating Fe powder and sulfur. The reaction is exothermic enough to make the reactants glowing red. I have not dried the piece of wood yet to test for conductance.

Cyrus,

I must say with some pride that I discovered the graphite and plastic (styrene) thing by myself some years ago by trial-and-error, like I said earlier in this thread. I’m not sure what plastic it was, but it worked against all odds, after all, plastics are supposed to insulate. In fact, It was the only thing I could make work fine until today. But is a thick goo, depending on the coarseness of the graphite, and it’s far from being the perfect conductive paint.

1000in^2? sounds a big project but, spare me the units conversion, what is the diameter of the thing?

[Edited on 22-5-2004 by Tacho]

Cyrus - 22-5-2004 at 14:41

To get the silver in a nonpolar solvent, first dry it in a chamber with CaCl2.

Here is my theory on how to get colloidal silver, which I am making up on the fly.
Get a silver salt and mix it with a soluble oxalate salt. Silver oxalate might precipitate, which you then heat up to decompose into Ag and CO2. In some other thread this method was used to make pyrophoric iron powder.

Yes, my styrene-xylene mix was rather thick too, I wonder if polyurethane would work- I will try and post the results.

The vdg sphere is about 47 cm wide- actually it is not a sphere, the top half is a sphere and the bottom is a donut. I forget the correct name for this configuration.

Tacho - 23-5-2004 at 04:21

The AgS dark coating does not seem conductive. If this H2S thing works at all, certainly is NOT spetacular! Maybe I’ll do some further tests. Maybe not.

Solutions of AgNO3 and/or CuSO4 mixed with hydroquinone and ammonia, give a thick black solution. and some fine, slow-depositing precipitate. I believe the black liquid (actually dark brown) is colloidal metal, and the precipitate is fine metal powder.

I could not make wood or paper conductive after many layers of that black liquid, but I have hope on the precipitate.

Why didn’t I stick to the hydroquinone/AgNO3/water/ethanol/(light?) clean silver precipitate? Because the I had the black liquid by accident, decided to research it before I go back to that silver. Besides, a good conductive copper powder would be much cheaper and readily available.

About hydroquinone: I use it because I have a lot of it. Probably other reducers can be used. In fact, I should try Kodak D-76 developer. It has about 5% hydroquinone in it, and is internationally available under the same D-76 denomination.

I’ll be traveling for a couple days, and won’t be able to continue my tests.


Cyrus,

Yes, I believe drying and mixing with non-polar solvents would work, if the powder don’t cake too badly, but I’ll try other options first.

Would the oxalate thing work wet? I mean, boil the water solution and silver precipitates as CO2 bubbles away? Sorry, I don’t have time to research now.

Cyrus - 24-5-2004 at 21:03

-From this webaddress

http://64.233.167.104/search?q=cache:ipsKj2uCrqwJ:www.intox.org/databank/documents/chemical/oxalicac/cie358.htm+decomposition+of+silver+oxalate&hl =en&ie=UTF-8

-I got (for oxalic acid)

Melting Point: 101.5 deg C (215 deg F) (dihydrate); 187 deg C (369 deg F) (anhydrous) melts and decomposes; sublimation begins at 100 deg C.
Boiling Point: Range 149-160 deg C (300-320 deg F) (dihydrate); sublimes with partial decomposition.

-And the following-

Incompatibility - Materials to Avoid:
BASES - vigorous reaction may occur, yielding heat and pressure

OXIDIZING AGENTS (eg. sodium chlorite, sodium hypochlorite) - may react violently or explosively

SILVER - May form explosive silver oxalate.

-so no, I doubt it will work in soln.

Tacho - 27-5-2004 at 08:38

I am trying to get a surface resistance smaller than a few dozen ohms/mm.

My failures:

I could not make a conductive paint using silver or copper precipitates. The strips of paper or woodsticks painted with this precipitates (with or without binders) result in very high surface resistance in the best cases. Hundreds of kOhms/mm.

H2S makes a paper treated with AgNO3 (exposed to sunlight, in case it makes any difference) turn from brown to black in an impressive way. But the resistance of the surface is the same hundreds of kOhms/mm. Graphite powder rubbed on the surface does the same and is not a deadly poison.

Strips of paper soaked with AgNO3+gelatin, exposed to sunlight and “developed” using hydroquinone or Kodak developer show no impressive results.

This is pure madscience: tin heated to orange-hot on a Ni-Cr wire does not deposit in a near graphite electrode even if I make a 15kV discharge between the two. Yes, I did that. :) Please, don’t mention vacuum, I know, I know.

My hope:

Silver halides. I hope to cover a surface with silver halide somehow and expose it to sunlight. My idea is to make a gelatin with AgNO3 and, after dry, expose it to sodium bromide. Or the other way around. If anybody knows a solvent for a silver halide, let me know.

I remember seeing some b&w photos with silvery spots in the blacks due to, I presume, bad fixing bath. If I can fix the halide badly enough, maybe it will be conductive.

I have an idea about electroforming a retort:

Cover a paraffin mold with very thin aluminum foil (they used to have those in some candies, haven’t seem them recently) , electroplate it quickly, melt the paraffin, dissolve the al away with NaOH.
This may be tricky, since al may react with the electroplating bath. It sure reacts with CuSO4, but if you are quick... Or use a thicker al foil...
I may try this in the near future.

[Edited on 27-5-2004 by Tacho]

Cyrus - 27-5-2004 at 15:17

I don't see the problem with high resistance coatings- as soon as you start plating it shouldn't be a problem
The real goal in my opinion is adhesion of the layers (for my application) - graphite powder rubbed on may have the same electrical resistance, but it doesnt have much adhesion. Which is a good thing for electroforming though.

I like your high tech method of tin sputtering.:P I was thinking about using the Al metal vaporized by sparks from a large battery to make mirrors though.
Maybe if you put it in helium...

IIRC, to electroplate on Al, you need to first zincate it- dip the Al piece in a bath with Zn2+ and NaOH. Then electroplate onto the relatively smooth Zn coat.

Here's a random idea- to make a copper test tube fill a glass one with copper oxide and strongly heat, then dissolve the glass in NaOH.

axehandle - 27-5-2004 at 15:54

Quote:

I don't see the problem with high resistance coatings- as soon as you start plating it shouldn't be a problem

It's actually very difficult when you come to the inevitable endpoint: plating Ti with Pt. If anyone could give me pointers, I'd be eternally grateful -- I want to plate a big Ti plate with Pt using nothing but water, HCl and hexachloroplatinic acid.

BromicAcid - 27-5-2004 at 16:39

How about a low melting alloy, most take advantage of gallium, one, the gallium-indium-tin melts at 10C, just keep your electolyte solution lower then this and it should stay solid and conduct, afterward you could easily melt it out. But gallium and indium tend to contribute to the high prices which make this unreasonable. How about something like Wood's metal, it has a Mp of 70C but that is a little high to put it over something like wax.

axehandle - 27-5-2004 at 16:58

Quote:

How about a low melting alloy, most take advantage of gallium, one, the gallium-indium-tin melts at 10C, just keep your electolyte solution lower then this and it should stay solid and conduct, afterward you could easily melt it out. But gallium and indium tend to contribute to the high prices which make this unreasonable. How about something like Wood's metal, it has a Mp of 70C but that is a little high to put it over something like wax.

Makes sense, but as I've understood it, electroplating Ti with Pt is VERY difficult (since Ti passivizes in almost any atmosphere), and I've found little to no info about it :(.

Tacho - 28-5-2004 at 03:40

Cyrus,

My experience with plating high resistance surfaces is that the metal deposits in the contact with “wire” and keeps depositing there because its the path of least resistance. Literally.
Industry circumvents that somehow. That’s why I used a mesh of thin copper wire backing my styrene-graphite mold, all insulated with a layer of pure plastic goo.

People say metal sputtering can be done with a lower vacuum, but what do they call a lower vacuum? Compared to what? Sam Barros at the Powerlabs page claims he made a sort of plasma ball using a refrigerator pump. Would that be enough? If I get obsessed enough with this, I may try.

http://www.powerlabs.org/plasmaglobe.htm

Thanks for the Zn tip. Do you think a dip in a ZnCl solution would do the trick?
Hey everybody! This is a good idea here!

Sorry, Cyrus, but I didn’t understand the copper tube thing.
Sorry axehandle, but I’ve never seen a piece of pure Ti or Pt in my life (only your pictures) and I can barely plate copper. Can’t help you.

Bromic Acid,

Why not tin? Most low melting point alloys are expensive or have cadmium. Or both. Tin melts pretty easy under a blowtorch or in an oven. I once bought relatively pure tin in a welders supply.
Common solder has lead, but what the hell, just be carefull, recicle and don't use the kitchen oven.

Cyrus - 28-5-2004 at 16:53

I think you will need NaOH too, IIRC it exposes the Al metal so that the reaction can take place.

The copper idea is a little wierd I admit, but because 2CuO-> 2Cu + O2
I was thinking that if you heated CuO in a test tube it might deposit Cu in a film, but it would pobably be a powder.

Tacho - 1-6-2004 at 03:34

I made six gels, using gelatin, agar and alginate. three with AgNO3, three with NaBr. Only agar became a really solid gel. I wetted the NaBr gels and goos with AgNO3 and vice-versa. Exposed to sunlight to dryness, tested for conductance, “developed” with Kodak photograph developer, dried, and tested again. All failed.

Thin aluminum foil is corroded away in my attempts to plate it with copper. I tried to do the ZnCl/NaOH thing with no good results. By the way, ZnCl reacts with NaOH making a white insoluble, so you have to wash the Al between baths.

Failures, failures, failures...

However,

My crude attempts to plate Sn with copper were not fruitless. No, I could not make anything impressive, but the copper was there. Irregularly distributed on the surface, like oil and water paints mixed, but was plated. A black powder (?) formed where copper was not deposited.

I believe is a matter of preparing the surface of tin. Some acid dipping, maybe. Or the proper alloy...

chemoleo - 1-6-2004 at 04:03

Bromic: there are certain waxes that have a much higher MP than 70 deg C. Any modelling shop will have them.
Most likely they will have Woods metal too.

Tacho: Sorry I didnt have time to reread the whole thread - but how about Cu plating on iron? Have done that many times, works well. A CuSO4 solution suffices :)

IvX - 1-6-2004 at 04:49

Sort of off topic perhaps but for the Ti thing the new(ish) procces for Ti manufacture from TiO2 is electrlysing it out of molten CaCl.

I tried this once(ages ago) but I had to cut the experiment short(external circumstances).The Ti formed a small mass around the copper mesh and had small buble like hollows in it.

Perhaps you coukld try something like that to make the basic structure, sand it down ,and the electroplate?

Ps.
A factory made Ti ring costs about 50 bucks :p

Tacho - 1-6-2004 at 08:02

Quote:
Originally posted by chemoleo
(snip)
Tacho: Sorry I didnt have time to reread the whole thread - but how about Cu plating on iron? Have done that many times, works well. A CuSO4 solution suffices :)


The idea here is to plate on a conductive mold that can be easily made and removed (washed, dissolved or molten).

You gave me an Idea! Fe or Zn powder in agar matrix. Expose it to CuSO4 solution, copper cristals grow and touch each other making the whole thing conductive. Better yet: copper powder and silver solution.

I'll try it and post.

Tacho - 9-6-2004 at 15:40

Who told me how to use FTP right? Organikum!
Who gave me good information on yeast reactions (and booze as a bonus)? Organikum!
Who is always there with good answers and a helping hand? Organikum!
Who told me to use zinc spray to get a conductive coat? Organikum!
Did I listen? NO! Did I say thank you? NO! Why? Has to be that damn mercury poisoning!
Bad Tacho! Bad Tacho!
What did I get when I stained my fingers with silver nitrate and poisoned my body with ominous chemicals? NOTHING!
What did I get when I followed Organikum's advice and sprayed a zinc “cold galvanizing” paint on my mold?

Well, we have to slow down here...

The zinc spray sold here as “cold galvanizing” (they claim "over 95% zinc powder";) does not make a conductive coat by itself (I can't understand why), but makes a surface that gets coated with copper if dipped in a strong copper sulfate solution. It’s by far my best result until now. Just a few dozen ohms per centimeter in my first attempts! I’m sure it can be improved vastly.

I have never seen nothing like this procedure described anywhere, so I guess Mad Science is, again, in the cutting edge of kitchen chemistry!

Whip me Orgy! Whip me hard!

Someones calling me?

Organikum - 9-6-2004 at 16:59

Uuups here I am!

The zinc spray makes no conductive coating at once as the zinc particles are covered with a very thin layer of epoxide or such for adhesion reasons. The copper sulfate etches this away and so it works.

But meanwhile I found something whats probably better:
Dipping the mold into a solution of SnCl2 should form a conductive layer on plastic and even glass - an transparent layer too. This can be electroless or electrolytically plated (a thin layer of copper deposited from the sulfate might be advantageous - its to be tried).
SnCl2 is the way it is done in industry - it replaces the rather expensive treatment with Pd-salts which was used before.

Thanks for the flowers :D

Tacho - 9-6-2004 at 17:15

Quote:
Originally posted by Organikum
Uuups here I am!

The zinc spray makes no conductive coating at once as the zinc particles are covered with a very thin layer of epoxide or such for adhesion reasons. The copper sulfate etches this away and so it works.


Interesting, I just worshiped you and now I totally disagree with you! I think the zinc is partially exposed and is displaced by the copper as it happens when you dip iron in copper sulfate. It just grows in fractal crystals, touching each other and making the whole thing conductive.
Quote:

But meanwhile I found something whats probably better:
Dipping the mold into a solution of SnCl2 should form a conductive layer on plastic and even glass - an transparent layer too. This can be electroless or electrolytically plated (a thin layer of copper deposited from the sulfate might be advantageous - its to be tried).
SnCl2 is the way it is done in industry - it replaces the rather expensive treatment with Pd-salts which was used before.

Thanks for the flowers :D


Eeeeh! Disagree again... The tin or palladium bath is used to create some sort of nucleating points for electroless deposition (maybe electrolytic too) but doesn't make the surface conductive.

(remark sniped by edit)



[Edited on 10-6-2004 by Tacho]

Organikum - 9-6-2004 at 18:45

Ehem.
If you use zinc-spray of higher concentration it will be conductive - mine was.

Of course the copper replaces partly the zinc and if you let it in the bath very long it will be displaced almost completely - not absolute completely as the copper grows on the zinc and protects it in parts. Called "zinc promoted copper".

Oh, that SnCl2 doesnt produce conducting tranparent surfaces on glass and plastics this is not only new to me but also to the Kirk-Othmer and a whole industry producing products by this method.
You are right, there exists the method of forming nucleating points with Pd and tin salts. And there exists the method for forming conducting layers. One doesnt exclude the other, actually the first is necessary for the other to work.

I believe we have to train this "worshipping" a little bit better, I am NOT REALLY SATISFIED! :mad:

;)

Tacho - 10-6-2004 at 02:34

Sorry mighty Organikum. Once again you showed me the path and once again I went in the wrong direction.

I'm still uncomfortable with the SnCl2 idea though.

I guess HCl+H2O2+tin will make me some SnCl2.

Polverone - 10-6-2004 at 08:28

Skip the H2O2 if you want SnCl2. I've found that aqueous HCl attacks at least high-tin alloys (lead free solder) at a reasonable pace. Does it not do the same for your tin?

Organikum - 10-6-2004 at 10:15

Quote:

Skip the H2O2 if you want SnCl2. I've found that aqueous HCl attacks at least high-tin alloys (lead free solder) at a reasonable pace.

As long the alloys contain some copper thats true. ;)

Cyrus - 10-6-2004 at 13:23

Zinc paint is great so long as you don't care about adhesion.:( I've tried and the immersion plating that results doesn't adhere. Oh well, thats my problem, not yours. Just finished finals, the experimenting level is getting kicked up a couple notches.

I don't get the SnCl2 method- could some one explain it to me. SnCl2 is a good reducing agent, but what is it going to do to glass? It is depositing tin? Is the reaction something like 2SnCl2 --> Sn + SnCl4. Sorry, this is a completely random guess. And if it doesn't form conductive coatings/nucleating points withoud Pd, why are we even trying?

Tacho - 10-6-2004 at 16:39

A paste of zinc powder mixed with gypsum, after hard, also develops a conductive copper layer when dipped in CuSO4 solution. The surface is not very smooth though. I’m waiting for samples made with zinc powder and sodium silicate to dry. My quest now is for a smooth very conductive surface. I’m thinking of making zinc pastes with shellac, gelatin, agar, alginate, ceramic etc. And try other copper salts, specially acetate, in various solvents.

“Cold galvanizing” zinc spray is, after all, a bit conductive, but in the same range as graphite powder or silver sulfide. Too high a resistance for me.

I have pure tin, and could only make the salt electrolytically. HCl did not react even with H2O2. At least not fast enough. None of the tests I made showed a hint of low resistance neither on glass nor plastics nor organic substrates.

Cyrus,

As I understand it, you are trying to make something like a sphere (almost) with a diameter of 47cm of... say... fiberglass, make it conductive, electroplate the outside of it with copper and then with silver?

Ok, I’ll risk to sound like an idiot trying to teach someone who may know more than I, but here I have some observations connected to this idea:

1) the final surface has to be mirror polished to achieve higher voltages, right? Any grain on the surface and there goes the electrons into the air. Well, every deposit I have seen until now (in my tests) is far from smooth.

2) the surface does not have to be very conductive, does it? I mean, only very, very low currents are involved, so charges will built even in a polished graphite paint, won’t they? I really don’t know the dynamics of holding charges in a Van der Graff.

3) you will need a HUGE bath to plate this thing. Isn’t this a problem?

4) why are you so concerned about adhesion? If you have a metal layer on the fiberglass(?) substrate, who cares if it is very adherent or just hanging there?

[Edited on 11-6-2004 by Tacho]

Cyrus - 10-6-2004 at 19:50

Yes, the surface needs to be EXTREMELY smooth otherwise all the charge dissapears- not even a dust grain.:(

That is why I have to sand the bondo (pretty close to fiberglass) layer for so long! And then put the conductive "paint" on top and make sure that is perfectly smooth. And then the perfectly smooth copper plate. (which is why only BRIGHT copper works) And then the perfectly smooth immersion plate of silver.

Nothing too hard, might take a couple of minutes or so.:D

I could have covered the whole thing in aluminum tape, but I am more than somewhat of a perfectionist.

I am obsessive about adhesion because the people at pupman.com have had problems with coatings flaking off of their toroids. (for tesla coils) But if no other options are found, I might have to go with the zinc paint.

Thankfully, I don't have to use a 500 gallon plating bath! There is a method called brush plating- connect one wire to your object to be plated, connect the other to a corrosion resistant brush- for copper plating it could be a copper brush with some chem. resistant fibers, dip the brush in the plating solution, and paint and plate away, very useful for in situ. and large object plating.

Edit- just saw your question about how much conductivity even matters to a VDG.

The main reason is that when the lightning discharges from one point on the sphere, all the electricity has to race over the surface to that point, and the less conductive the surface is, the smaller the discharges are.

Also, if the coating is too thin, ie gold foil or thin layers of graphite, the discharge tends to vaporize and burn holes in the conductive layer.

Here are some random things-

If I coat the sphere with a nickel plate, some sites say that during the discharge nickel carbonyl will form. Ahh, Healthy. :o
Does anyone have info on this? It might be a way to make the useful but very toxic and flammable/explosive compound.

I love pottery stores! 227 g BaCO3, 227 g MnO2, 183 g Fe3O4, about 1L of fluffy MgCO3, and 30 g CrO3 (chrome plating), all for $4.53!









[Edited on 11-6-2004 by Cyrus]

Nixie - 17-12-2006 at 22:11

Quote:
Originally posted by Cyrus
I've got a formula on this too.

1 oz/gal AgNO3
14 oz/gal Na2S2O3
10 oz/gal NH3 (Is it household strength ammonia or pure ammonia?!- probably household. Elsewhere you are supposed to add enough to make the silver precipitate Ag2S2O3? that forms dissolve.)

I'm interested in electroless silver plating for copper tracks on printet circuit boards, and would like to avoid buying a commercial solution. My question regarding your recipe is where to get the Na2S2O3, or whether there's an easy to obtain or prepare substitute.

Tacho - 18-12-2006 at 02:49

Add a solution of table salt to a solution of AgNO3 and you have a white silver chloride precipitate.
Silver chloride powder, mixed with some table salt and a binder like kaolin can be used to plate copper. Just rub strongly the humid (almost dry) powder on the clean copper surface and it takes a silver covering. You must rub strongly to obtain a shiny, resistant silver coating.

Nixie - 18-12-2006 at 12:39

Is there any other way from Ag to the chloride (since I'm starting with Ag, not the nitrate).

The_Davster - 18-12-2006 at 13:08

You should be able to by use of a silver cathode in a salt(or perhaps HCl) solution. Assuming of course that the precipitated AgCl does not cling to the electrode too much.

EDIT: HCl is preferable I think, especially in an undivided cell, otherwise Ag2O may contaminate.

[Edited on 18-12-2006 by The_Davster]

Nixie - 18-12-2006 at 13:16

Great! Any substitutes for the binder? I shall try this procedure as soon as I can.

The_Davster - 18-12-2006 at 21:37

Yeah, AgCl builds up very fast on the silver, but the silver chloride sticks to the electrode stopping further reaction. If the silver electrode was flat and placed on the bottom of the beaker under a stirbar it would work. The AgCl comes off the electrode with mild scraping.

Tacho - 19-12-2006 at 03:29

Binder is not really necessary, just salt and AgCl on some toilet paper, it probably works anyway.

hashashan - 19-6-2007 at 01:00

Guys i found this :
http://www.google.com/patents?id=dFpyAAAAEBAJ&printsec=a...

it does look promising, however do you have an idea what sodium phosphate did they mean there?

btw. sorry for the bump, but i do believe there is some interest in it

[Edited on 19-6-2007 by hashashan]

franklyn - 4-7-2012 at 13:42

Electroplaters view of Physical Vapor Deposition Processing
http://infohouse.p2ric.org/ref/25/24745.pdf
A very thorough comparison with electroplating and other methods of metal coating.

Another useful thread here _
http://www.sciencemadness.org/talk/viewthread.php?tid=1990#p...

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Saturday Night Special

franklyn - 10-8-2012 at 08:12

www.businessinsider.com/it-is-now-possible-to-download-and-3...

It's entirely possible to use ceramic powder which is sintered much as clay pots are
fired in a kiln to make firearm parts which cannot be seen by a metal detector.

resources
www.websiteslike.org/site/makepartsfast.com

Paste this into Google => desktop manufacturing
click on the "Images for desktop manufacturing" link below

_____________________________________

somewhat related
www.sciencemadness.org/talk/viewthread.php?tid=20889

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argyrium - 2-8-2016 at 15:47

I happened upon this very interesting clip showing a recent development of a nano-Ag based "ink".

Silver based "ink" for electrical conductivity - in a pen.

a clip: https://www.youtube.com/watch?v=zRbQvEefhXc#t=39

and the site:

https://agic.cc/en

and a paper:

Attachment: p363-kawahara.pdf (7.7MB)
This file has been downloaded 374 times

Hope it will be useful for someone here.