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aga
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[*] posted on 14-2-2018 at 11:12


Found place locally that sells MAPP gas & torch !

torch.jpg - 33kB

Certainly melts the glass faster than the other stuff.

Pretty quickly got 3x drops:

drops.jpg - 40kB

Sticking them in a plastic bag and snipping off the tail did bugger all :(

cut.jpg - 40kB

Has anyone made one yet that works as advertised, i.e. explodes when the tail is snipped off ?




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happyfooddance
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[*] posted on 14-2-2018 at 11:57


Maybe try dropping them in oil, not water?

https://en.m.wikipedia.org/wiki/Leidenfrost_effect
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[*] posted on 14-2-2018 at 12:04


Nah.

It's about the skin cooling faster than the interior rather than just a skin effect.

I'll have another go tomoz.

The three i tried 20 mins ago were all dropped into the same pot of water.
The last one fell to bits and the first two seemed to explode, so it's looking better.

It seems easy to get a blob of tear-shaped glass, harder to get those internal stresses going on.




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[*] posted on 14-2-2018 at 12:15


How is the skin going to cool faster if water vapor is creating an insulating layer...?

If you want to create extra stress, you can start with soda-lime glass and do an ion exchange deal (Na->K), this is ubiquitous nowadays and I am sure you can find refs. for the process.

As for writing off my suggestion, you are one who is always saying it is worth a try. And I only mention it because I know it has worked for others... And you seem to be having little success.

How hard can it be to set up a pan of oil, aga?

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[*] posted on 14-2-2018 at 12:28


The molten salts- What is a eutectic mix of reasonably cheap ones.

I recall that some people who make Lead shot at home by dripping molten Lead into liquid from far enough above to allow time for surface tension to pull the drop spherical and air flow to get the drop skinned over with solid Lead use glycol antifreeze for the liquid. They can tailor the hardness produced somewhat by the speed of the chill/temperature of the liquid in the bucket (faster chill = harder for Lead alloyed with Antimony/Tin/Arsenic- Why ammunition manufacturers tout their products as containing "chilled shot")

Drip a drop into a cup of glycol antifreeze just out of the refrigerator, that is, antifreeze without water admixture. No Leidenfrost effect? Go the other way- Room temperature quench? Just under smoke point quench?


[Edited on 14-2-2018 by Bert]
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[*] posted on 14-2-2018 at 12:34


Quote: Originally posted by happyfooddance  
How hard can it be to set up a pan of oil, aga?

Sorry, you're quite right. It's not hard to do at all.

I look forward to seeing your photos of Success on the morrow.




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[*] posted on 14-2-2018 at 12:55


Quote: Originally posted by aga  
Quote: Originally posted by happyfooddance  
How hard can it be to set up a pan of oil, aga?

Sorry, you're quite right. It's not hard to do at all.

I look forward to seeing your photos of Success on the morrow.


Bro, this is me trying to help you out with YOUR project. I for sure have my own projects, but I don't think they fit in this thread and I don't want to start a new one when I can UTSE just fine. Also, I am taking care of my 12 month oId son. But good luck with YOUR project.
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[*] posted on 14-2-2018 at 12:55


Here are some air-cooled "dud" glass drops, used as jewelry:
https://store.sundropjewelry.com/blogs/news/ive-heard-of-a-p...
Here's another from quenching in LN2 (low temperature, but low heat capacity/heat of vaporization, and lots of vapors to interfere with the cooling process:
http://www.scienceforums.com/topic/30128-molten-glass-droppe...
The quench conditions seem very important, and are an easy parameter to change. However, some of the experiments here have lead to the drops breaking during cooling. Perhaps the glass composition matters too? Do some glasses have more capacity to bend before breaking? It seems like the ultimate combination would be a high coefficient of thermal expansion, a moderate to high elastic/bulk modulus (so it would deform or compress only slightly for a given force), and the ability to flex a lot (for a glass bulb) before breaking. That way, the glass wouldn't shatter itself while cooling, but would have a lot of elastic energy stored inside.
Another thing, is that molten glass gets much less viscous as its temperature goes up. Could the temperature prior to hitting the water be a major parameter?
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[*] posted on 14-2-2018 at 13:06


Regarding brittleness? Look in this table of materials for some clues.

https://www.makeitfrom.com/material-group/Glass-and-Glass-Ce...

Check the Poisson's ratio for your material- A higher number = less brittle.

For example:

Fused quartz = .17

Vycor "glass" = .19

Borosilicate glass (Schott brand) = .20

Soda lime glass = .23 (approximately, for annealed float glass, lots of variation)

Mild steel = .30 - .35

Rubber! = .45 - .5 (effectively, .5 is the limit)

I suspect the figures given for heat conduction would be of some interest here too.
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[*] posted on 14-2-2018 at 13:10


https://www.youtube.com/watch?v=0KaWSOlASWc

Lou Reid.

The relevant lyrics are at 1:23 to 1:41, then again at 3:17 to 3:44




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[*] posted on 15-2-2018 at 10:55


Had another go today, making 7 'drops', 4 out of borosilicate, 3 out of soda-glass (a smashed up drinking glass).

The borosilicate ones tend to easily form into a droplet, yet have zero activity.

The 'normal' glass doesn't crack up easily with the MAPP gas torch during heating, yet shatter after a few seconds in the water - the glass just cracks into bits before a droplet forms with a butane torch.

A random utoob comment says it is easier with soda-lime glass, although borosilicate glass can be done.

So far i think the soda-lime glass droplets are the way forwards, as they at least self-destruct at some point, i.e. after a few seconds, whereas the boro ones have done nothing so far.

Every attempt took at least 10 mins heating to get a droplet to form & fall into the water.




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[*] posted on 15-2-2018 at 12:21


Quote: Originally posted by aga  


Every attempt took at least 10 mins heating to get a droplet to form & fall into the water.


Sounds like you aren't using your torch properly. Tip of the blue, seems like good advice.
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[*] posted on 15-2-2018 at 12:34


Quote: Originally posted by happyfooddance  
Sounds like you aren't using your torch properly. Tip of the blue, seems like good advice.

To be honest i think you're absolutely right.

So far i've been clenching the torch in my bum-cheeks while suspended upside-down from a roof beam with the glass pieces held in my teeth.

Contorting to get the glass & flame to even get in contact has been really hard.

Lost both eyebrows yet only one load of nostril hair. Wish i had done more Yoga to get both.

For the next attempt i will take off the monkey trousers and the scuba flippers to see if that helps.




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[*] posted on 15-2-2018 at 12:37


Quote: Originally posted by aga  
Quote: Originally posted by happyfooddance  
Sounds like you aren't using your torch properly. Tip of the blue, seems like good advice.

To be honest i think you're absolutely right.

So far i've been clenching the torch in my bum-cheeks while suspended upside-down from a roof beam with the glass pieces held in my teeth.

Contorting to get the glass & flame to even get in contact has been really hard.

Lost both eyebrows yet only one load of nostril hair. Wish i had done more Yoga to get both.

For the next attempt i will take off the monkey trousers and the scuba flippers to see if that helps.


Maybe it would help if you just used the search engine.

Edit: or maybe drink less...???

[Edited on 2-15-2018 by happyfooddance]
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[*] posted on 15-2-2018 at 13:04


It'd help if people talk Less and Do more.

Unlikely that will happen in my experience.

I'll burn the rest of this MAPP canister to see if i can help Bert achieve at least a functional 'drop' so he can test if it can make other stuff go BOOM.

To be fair to Bert, who could/should be trying all this out, i'm personally too scared of explosives to go anywhere near what he proposed, so i'm really happy to be able to at least contribute to the Prince Rupert's Drop synthesis.

Glad Bert has Not wasted his time on the 'drop' part too much, as it is the most facile part of his idea, yet has proved elusive to ACTUALLY produce.

A google page does not equal a working method.

(one requires actual physical time and effort, the other just needs internet and desire to sputter words all over)




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[*] posted on 16-2-2018 at 11:22


A lot of searching turned up endless piles of droppings with hardly any real info at all.

Presumably happyfooddance's oil suggestion comes from a brief passage in GlassWorking_OCR.pdf which can be found in the SM library.

"The drops of glass produced by Prince Rupert of Bavaria by dropping molten glass into oil"

None of the dozens of other references found suggest oil - they all say water.

A utoob vid shows a method by which the drops are formed without touching the sides of the water container at all.

https://www.youtube.com/watch?v=8p5fnM1hcCY
(it's in German)

A random comment at http://www.instructables.com/id/Make-Prince-Ruperts-Drops-Gl...

"For those wondering, yes, you can make the drops from Boro (Pyrex) however, unlike soft glass or soda glass, they will not explode."

kinda suggests that lab glass is not a good way to go. Other random comments elsewhere either say the same, or that it is much harder to get to work.

Finally some actual Science was found here: http://www.livebinders.com/play/play?id=1997855

While the work does not discuss how to form the drops, the materials were 'feldspar' for the glass, and the data suggests that either boiling water or ice cold water works much better than water at 26 C, which is what it's been here recently.

Another thought is that while glass is pretty crappy at conducting heat, it might be a good idea to reduce the mass to be heated, also disconnect it (thermally) from whatever it is being supported by.

So, for tomorrow's attempt(s) i'll be trying :-

Ice cold water
A smashed up jam-jar (soda-lime glass)
Once melting, pull the glass above where the bead will form to make a thinner connection
Heat only the bead, not the bit above it
Remove heat once the beat starts to descend, so as to let it go into the water without fully disconnecting from the supporting mass.

That last bit should let it become immersed without letting it touch the side or bottom of the glass of water.




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