Sciencemadness Discussion Board - Grease sources for glassware joints?

Grease sources for glassware joints?

Biochemscientist - 18-8-2011 at 22:43

Hi all,

I recently obtained my first distillation set and will soon be embarking on a few distillation projects. I am new to working with this type of glassware, and I one thing I am wondering is about greasing the joints. Is greasing required, or is it optional? Are there any readily-available substances that will function for this purpose such as glycerin or petroleum jelly, or is it necessary to order a special type of grease?

Thanks!

hkparker - 18-8-2011 at 22:55

required! Don't do what I did when I got my first ground glass joint and just put them together, they can easily be stuck without lubrication.

I have always used vasaline (petroleum jelly) and it works great. I would not use glycerin. Other substances such as silicon oil or teflon tape are sometimes used but for most everything petroleum jelly does great.

Bot0nist - 19-8-2011 at 03:12

Also, look for plumbers silicon grease. It is very unreactive and a lot cheaper than buying 'vacuum grease.'

woelen - 19-8-2011 at 03:50

Another important thing is to use a VERY thin layer of grease. Keep in mind that the grease may dissolve in some compounds and may contaminate what you are distilling.

I do not always grease the joints. Sometimes the compound to be distilled is a perfect agent for sealing the joints. In such cases I take some of the liquid to be distilled and _slightly_ wet the joints with that.

In some special cases I use concentrated sulphuric acid for greasing. E.g. when I distill bromine or fuming nitric acid I do that. The concentrated sulphuric acid does not dissolve in bromine and it does not react with bromine, while most greases both dissolve and react. It does dissolve in fuming nitric acid and in that case the greasing must be particularly thin.

When I distill organic water-insoluble solvents (e.g. hexane), then I use water for 'greasing' the joints.

Arthur Dent - 19-8-2011 at 04:00

There have been many threads on this... again, i'll mention one particular type of grease that I have discovered is narly as good as the real stuff:

Left ot the picture above is automotive silicone dielectric compound. It's about $7 or $8 a tube, on the right is the "real thing" that's about $50 for one ounce!!!

Both are nearly similar in every point, chemically unreactive to nearly everything, and unless you do some hi-end analytical chemistry, will be perfectly suited for all ground glass joints.

The problem with vaseline is that it doesn't stand up very well to heat, kind of runs off, possibly contaminating the solution you want to isolate, and it reacts with certain hydrocarbons, effectively f***ing up your reactions in certain cases. And unless you have absolutely perfect-fitting joints, Silicon oil will not be adequate. Teflon tape is very good, but unless you tape the joint perfectly without the slightest crease in the tape, it won't be a good sealed joint.

That automotive silicone dielectric compound pictured above can be found at any Canadian Tire, or any automotive parts store like NAPA and places of that sort.

Robert

fledarmus - 19-8-2011 at 04:13

For whatever grease you are using, the key is to use as little as you need to avoid contaminating your reaction and everything else your glassware touches. When I use grease at all (which is very rarely), I apply a small amount to the top half of the inner joint and wipe it off with a paper towel, then put the joint together. The joint will appear white when it is put together completely dry, and will appear clear where there is a film of grease. You want a complete clear ring in the top half of the joint, and at least a complete dry ring at the very bottom of the joint. Otherwise you will be getting grease into your reaction.

Usually I only grease joints that will be subjected either to vacuum, long periods (several days) of reflux, or strong bases. So little grease is required that it is worth spending the money on a high-quality silicon high vacuum grease - it will take you a long time to use up one tube. I've never seen anything as expensive as $50 an ounce - even from a high end chemical supply house like Aldrich it's only about $6 an ounce. This is what I use: Vacuum grease

Vaseline is very soluble in most non-polar solvents like toluene and hexane, and tends to get into everything. Silicon oil is too thin and tends to run out of the joint.

**Edited to add this exception based on Arthur Dent's picture - I use much more vacuum grease to seal things like desicators and vacuum ovens than I use on reaction glassware. These are not coming into contact with solvents so they will not contaminate your reaction unless you touch them, and since the joints remain in contact for very long periods of time under vacuum, they do tend to freeze up if they are not used regularly and occasionally cleaned and regreased. Solvent stills, which also run constantly for long periods of time, are so hard to keep joints free that we've found it worth the money to add teflon sleeves (SciMar teflon sleeve) to each of the joints. Saves us a lot of broken glassware when we do eventually need to clean out the stills.

[Edited on 19-8-2011 by fledarmus]

Bot0nist - 19-8-2011 at 05:27

Quote: Originally posted by woelen

In some special cases I use concentrated sulphuric acid for greasing. E.g. when I distill bromine or fuming nitric acid I do that. The concentrated sulphuric acid does not dissolve in bromine and it does not react with bromine, while most greases both dissolve and react. It does dissolve in fuming nitric acid and in that case the greasing must be particularly thin.

Wow, I never thought of using H2SO4 to lube my joints in my HNO3 distillation. It makes perfect sense though. It's slightly viscous, and for my needs a little sulfuric acid contamination is not a problem. I'll be trying it this weekend. Thank you woelen!

[Edited on 19-8-2011 by Bot0nist]

redox - 19-8-2011 at 05:43

I would recommend just buying regular vacuum grease. About 5 months ago I bought 1/4 of an ounce of high-vacuum grease on ebay for $12, and I have barely broken the surface! Keep in mind that I have used this frequently. A little bit of grease goes a long, long, way.

Also, it probably matters that I only use 14/20 and 14/10 joints, which are significantly smaller than 24/40.

User - 19-8-2011 at 08:08

I also would recommend using the real stuff, its very inert,at least when this is requires.
On any other occasion ,for example when distilling alcohol just use petroleum jelly.
It depends heavily on the application.

MeSynth - 20-8-2011 at 11:06

I'm sure that as long as you never apply a vacuum and you dont push them together harder than you need to in order to get the clip on you dont need lube for the joints.

Mildronate - 20-8-2011 at 13:16

I use vaseline or nothing.

magnus454 - 20-8-2011 at 15:41

Plumbers waterproof grease (HOME DEPOT) or REESE trailer ball hitch lubricant (TEFLON) found at many autopart stores, and outdoor sports stores

User - 20-8-2011 at 22:48

Quote:

I'm sure that as long as you never apply a vacuum and you don't push them together harder than you need to in order to get the clip on you don't need lube for the joints.

Not entirely true, when one distills highly volatile liquids the joints start to bleed, seen this happen on multiple occasions.

MeSynth - 21-8-2011 at 14:23

Quote: Originally posted by User

Quote:

I'm sure that as long as you never apply a vacuum and you don't push them together harder than you need to in order to get the clip on you don't need lube for the joints.

Not entirely true, when one distills highly volatile liquids the joints start to bleed, seen this happen on multiple occasions.

As long as your set up isn't closed (why?) then it shouldn't have the pressure needed to escape through the joints. The flow of gas/pressure will flow out of the set up just like it would with the joints greased unless your glassware is no good or the joints have been damaged. Plus! Say your distilling your "volatile liquid" and you just greased your joints. That gas is going to touch the grease and possibly react with it and possibly contaminate what ever it is your distilling.

hkparker - 21-8-2011 at 14:32

Quote: Originally posted by MeSynth

I'm sure that as long as you never apply a vacuum and you dont push them together harder than you need to in order to get the clip on you dont need lube for the joints.

The fact that joins can become welded together means you need lube. Otherwise it is likely that they will get stuck, even if you don't push them together very hard.

But as woelen said, many different compounds can be used as lube depending on what your distilling as to reduce contamination.

Bot0nist - 21-8-2011 at 15:20

Quote: Originally posted by MeSynth

Quote: Originally posted by User

Quote:

I'm sure that as long as you never apply a vacuum and you don't push them together harder than you need to in order to get the clip on you don't need lube for the joints.

Not entirely true, when one distills highly volatile liquids the joints start to bleed, seen this happen on multiple occasions.

It is very unlikely to react with silicone grease.

Volatile liquids do bleed out the joints. Just the other day I was drying some solvents and the methyl ethyl ketone was seeping out of one of joints, even though I greased it. Stinky stuff.

[Edited on 21-8-2011 by Bot0nist]

redox - 21-8-2011 at 15:36

Quote: Originally posted by Bot0nist

Quote: Originally posted by MeSynth

Quote: Originally posted by User

Quote:

I'm sure that as long as you never apply a vacuum and you don't push them together harder than you need to in order to get the clip on you don't need lube for the joints.

Not entirely true, when one distills highly volatile liquids the joints start to bleed, seen this happen on multiple occasions.

Methyl ethyl ketone = stinky? No! MEK smells like butterscotch; its nice.

Bot0nist - 21-8-2011 at 18:11

Not to me, It chokes me out. It will make your eyes water and your throat close up, trust me.
Kinda like as bad as toluene or MNT/DNT. All smell 'good', but if your get a breath full, you'll know it.
*cough,gag*

[Edited on 22-8-2011 by Bot0nist]

User - 22-8-2011 at 01:39

If it doesnt hurt the product one could even use some water to make the joints seal, someone pointed this to me once, dont even know if this is such a good idea..

Quote:

Btw my joints arn't bad, as pointed out by botanist, this just happens, I wish it didnt.
It really sucks when the glass is hot and running.

I can understand the people that dont want to buy the super expensive grease.
Im using the same tube for nearly 2 years,a speck is enough.
The stuff is just good and holds up to above 400 degrees.

CuriosityKilledtheKat - 25-8-2011 at 19:25

here is a website that teaches you how to make your own grease/lubricant probably the cheapest way to go about it too i'll have a crack at it one day soon...

www.instructables.com/id/Personal-Lubricant/

redox - 25-8-2011 at 19:49

Quote: Originally posted by CuriosityKilledtheKat

here is a website that teaches you how to make your own grease/lubricant probably the cheapest way to go about it too i'll have a crack at it one day soon...

www.instructables.com/id/Personal-Lubricant/

You're joking, right?

I'm pretty sure that that recipe gives a horrible grease/lubricant. When the water evaporates you would be left with a white powder (the cornstarch), which could only contaminate your reaction and it would be bad on the joints.

Also, maybe you didn't realize it, but that was designed to be a personal

lubricant... who would actually use that?!

[Edited on 26-8-2011 by redox]

MeSynth - 26-8-2011 at 00:50

Like I said before lube is not needed unless your glasswares joins are no good aaaannnddddd it is not desired unless a vacuum is being applied ffooorrrr the reason that even if the distillate doesnt react with the grease it can still cause it to come into solution with the distillate reeessullttting in contamination of the distillate. Use grease only when it is needed to pull a leak free vacuum, your joints are no good anymore, OR your highly intelligent brain decides that grease will be needed to insure nothing escapes through the joints and that contamination of the distillate or product of reaction will not be a problem.

User - 26-8-2011 at 02:58

Oke than the teachers at the lab-school I did were complete morons..
Never mind , not gonna start a flame war.

[Edited on 26-8-2011 by User]

redox - 26-8-2011 at 06:48

Quote: Originally posted by MeSynth

Like I said before lube is not needed unless your glasswares joins are no good aaaannnddddd it is not desired unless a vacuum is being applied ffooorrrr the reason that even if the distillate doesnt react with the grease it can still cause it to come into solution with the distillate reeessullttting in contamination of the distillate. Use grease only when it is needed to pull a leak free vacuum, your joints are no good anymore, OR your highly intelligent brain decides that grease will be needed to insure nothing escapes through the joints and that contamination of the distillate or product of reaction will not be a problem.

YOUR highly intelligent brain obviously forgot about joint freezing. You won't catch me in a million years not using grease on my new Aldrich Dean-Stark trap, or my three-necked flasks. I don't know if you have any ST glassware, but it really sucks to have a frozen joint, and using lube greatly lowers the chances of freezing.

zenosx - 5-2-2013 at 20:34

I use a lithium grease "pen" that is basically a stick of lithium grease wrapped in paper. I have been using it for a couple of years now, and as most have said, I lube the top or middle of the joint, leaving the lowest portion clean. Lubed portions will look "clear." I have never had stuck glassware using this compound, and have never had it contaminate any distillation/reflux etc that I have been doing.
You do need to use more of it for vacuum distillations, but it has never pulled through the joint into my rigs. I also use it on all of my glass on glass reagent containers with no issues, including my 98% HNO3 that had managed to eat through any other compound besides glass it was placed in.
A quick half/joint run around with the pen, and a quick twist always has worked, and since it is thick it actually helps to "glue" the joints together and prevent disconnections.
I find vasoline and others like it too messy and hve only used them when I had a high likelihood of joint freeze (NaOH, etc,)

wireshark - 6-2-2013 at 17:48

Another vote for vaseline

teflon sheeting

quantumcorespacealchemyst - 3-12-2014 at 18:05

i have been using teflon sheets from ebay and cutting them to double wrap around the joints. i have used them for diethyl ether and chloroform as well as boiling over nitric acid and fuming iodine. the times where i use the solvents, there is liquid that surrounds the joint and there is bubbling, although it seems to condense and not leave the joint, at least not much if it does. the smell is not strong exept for around the output of the condensor. i have been wary of the temperature though with say the diethyl ether.

i can't guarantee no leakage and you will have to try it to see what i mean with say chloroform or something. although the joints seem to wet fully, they don't seem to leak.

i usually wrap the sheet around the male joint and get an idea of an alright strip and use an exacto knife to trace around part, getting a rough idea, unwrapping, cutting the rest and then refining it on the male joint. using a compass and drawing out the arc can make a good template for making many economically after hacking at it. i have done this for the 14/20 and don't have paper or compass wide enough for the other ones currently.

hope this helps

subsecret - 3-12-2014 at 19:15

I use Teflon tape for my joints, and it seems to work well. Keck clips can be a problem, because the thin layer of tape expands the joint slightly. I used to use vaseline, but this was hard to wash off, and as stated, not very inert.

I avoid using vacuum grease because I don't want to put in the extra time to clean the joint after each use. Washing with soap and a distilled water rinse is the usual treatment for my glassware. How do you more experienced members get that Corning grease off your glassware?

Ethyl Acetate, link and mention at bottom

quantumcorespacealchemyst - 3-12-2014 at 23:21

yea, i have been using extra clamps to secure the apparatuses in place i dont have keck clips and have realized they may not fit. i am not that experienced or have used corning grease and will say also that for non heavy cleanup, BORAX has worked great for me, and letting flasks and stuff soak in a bucket of it for a week or so had dislodged some organic gunk that came with my flasks (i made pirahna solution and then realized that the H2O2 bleach was 3-5% not 30%, which explained the black dots not dissolving, so i just dumped it in my wash bucket and forgot about it for a while and it wiped off easy when i picked it out again). i guess washing soda would have done the same and there may even have been a tiny bit of it in the water too, although i find when washing and rinsing glassware the BORAX has just the right bit of something, i don't know and the tiny bits of it that don't dissolve work good for abrasion and it doesn't hurt/burn and rinses off smoothly.
cleaning the the greases though, i have no clue about.

edit: these people have some methods.

the person rrkss says " Was able to clean my joints to a nice frosty color in a matter of seconds using Ethyl Acetate" and that it is a cheap and simple solvent

http://www.sciencemadness.org/talk/viewthread.php?tid=14023

[Edited on 4-12-2014 by quantumcorespacealchemyst]

forgottenpassword - 4-12-2014 at 02:24

For every day use (non-vacuum applications) I too am a big fan of vaseline. It works: it provides thermal contact between the two pieces of glassware, and it prevents the joints from freezing. Any that manages to contaminate your product is easily removed by washing with petroleum ether. The same can NOT be said of high-vacuum grease. It is essentially insoluble in anything and you will have have to re-chromatograph or re-distil your product if it becomes contaminated with it. Having said that, used-properly, there should be no risk of contamination whatsoever. Teflon tape I've never tried, although it does sound like an excellent and clean general method. But I'm rather fond of greasing joints the old-fashioned way, and see no reason to change.

j_sum1 - 4-12-2014 at 02:54

I would think that teflon will prevent heat conduction at the joint. I am by no means an expert here but if you were expecting a reasonable amount of thermal stress then you might want to rethink teflon tape -- even if it does provide a bit of extra give at the join.

forgottenpassword - 4-12-2014 at 03:58

Good point, that. Certainly there will be more stress on the glass due to different expansion rates; although borosilicate is quite superb in that department, so whether it makes any practical difference I don't know. Teflon does soften somewhat with heat. In fact it is quite 'soft' even when cold: as plumber's tape, anyway: so maybe it provides SOME thermal contact.

[Edited on 4-12-2014 by forgottenpassword]

Mailinmypocket - 4-12-2014 at 06:24

As mentioned above by Arthur Dent, dielectric silicone grease is the way to go. A tube lasts for ever and the stuff is surprisingly similar to the real stuff! Home Depot has one that also mentions vacuum uses:

forgottenpassword - 4-12-2014 at 07:34

Which is, what, half the price of Dow Corning high vacuum grease? The last tube I bought was 50g for £10. Is it really worth the saving? Would you use that on a high vacuum line?

[Edited on 4-12-2014 by forgottenpassword]

Mailinmypocket - 4-12-2014 at 07:52

It's not so much the fact that it's cheaper but rather much more accessible. I've only seen the Corning stuff at higher prices than that (then again I haven't spent much time searching for a deal on the stuff). Not entirely sure what the vacuum part is about though and So I have no clue how it would perform on high vac lines...

It beats the heck out of Vaseline on joints IMO

careysub - 4-12-2014 at 11:27

Quote: Originally posted by j_sum1

I would think that teflon will prevent heat conduction at the joint.

I don't think any joint dressing that works will prevent heat conduction. It is simply too thin to have a substantial effect.

lysander - 14-9-2015 at 19:12

I thought teflon (tape or plumber's paste) was unbeatable: Unless you're working with fluorines PTFE doesn't react with anything. Isn't silicone grease a little more reactive?

Deathunter88 - 15-9-2015 at 01:37

Another vote for not using grease. I have distilled ethanol, ether, sulphuric acid, acetone and many many more without a single drop of grease. And for all of them I got very very close to 100% yield based on starting liquid. Not once have I suffered a frozen joint.

The only time I have used grease (sulphuric acid) actually is when distilling bromine, and even then I felt that the "grease" was unnecessary.

Take my advice with a grain of salt, as it probably depends on the quality of your ground glass joints. I buy from (what I think) is the best manufacturer in China and their stuff is really top notch.

subsecret - 15-9-2015 at 16:07

I use plumbers' grease or PTFE tape for my joints, but in the case of bromine or nitric acid, I use sulfuric acid. It may be worth it to buy a tube of high vacuum grease and distribute it to members who need small amounts of it.

j_sum1 - 15-9-2015 at 16:14

I bought this
I figured that it would last almost indefinitely and I may as well have something that would work consistently well whatever the application. It didn't seem like a huge expense to me.

NedsHead - 16-9-2015 at 03:21

I bought my distillation kit from sciencesupply.com.au and highly recommend them but that is a lot of money for 50g of vac grease, I found a much better deal a few days ago http://www.ebay.com.au/itm/291406381912?_trksid=p2060353.m14...

edit: I just noticed they are the same grease!

[Edited on 16-9-2015 by NedsHead]

j_sum1 - 16-9-2015 at 04:10

I don't think I paid that much.
From memory it was $15 AU.

NedsHead - 16-9-2015 at 04:51

he has some good deals occasionally, you must have caught him at the right time. sometimes his prices are on par with the Chinese prices but without the loooong wait

macckone - 16-9-2015 at 07:06

United glass tech sells teflon seals.
Most lab supply places sell silicone grease.
Auto parts places have a variety of grease compounds.
For less sensitive reactions Vaseline works well.
Sulfuric acid is a standby for certain reactions.
Ptfe plumbers tape is also great.
And don't forget polyimide tape.