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Is it possible to melt glass with common equiptment?

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phisrow

Golden Member
The title pretty much says it. I've become interested in trying to make Prince Rupert's Drops a curious sort of internally stressed glass. The procedure is simple; but requires melting small quantities of glass.

I only have access to standard home/hobbyist equipment and supplies, so I was wondering if anybody had advice on how best to go about melting glass in small quantities for this sort of project?
 
Yes, this type of propane torch will melt at least the softer glasses. In fact, some torch kits came with a simple bent-wire accessory used to prop the tank/torch head up (it slipped around the neck of the tank) so the flame was aimed almost sraight up. Then you had both hands free to handle the glass.
 
In the absence of such a torch, you can use a rod of glass as a sort of resistor in a circuit - get some 12/2, toss a plug on one end. Run the other end outside and expose (unplugged at this point, duh) 6 inches or so of wire on the neutral and hot sides. Wrap each end around some glass, a few inches apart. Somehow manage to prop the glass up (cinderblocks) such that the center of the glass is above the ground (or above a dish of water used to quickly cool the glass, IIRC how to form such drops). Plug in the circuit. Carefully heat up the glass. Once it gets hot enough, it will start conducting. A bit hotter, and the resistance of the glass is low enough to allow a current, but high enough to cause the heating to run out of control. It'll melt.
 
Thanks for the suggestions, guys. I picked up a propane torch this afternoon and made a few attempts.

My best results are still only a few millimeters in size; but they do actually work, which makes the whole project rather exciting.
 
Originally posted by: phisrow
Thanks for the suggestions, guys. I picked up a propane torch this afternoon and made a few attempts.

My best results are still only a few millimeters in size; but they do actually work, which makes the whole project rather exciting.
Click to expand...

good job. post some pictures if you get a chance. i'd like to see what you've created.
 
Hmmm... now that I think about it, this would be a neat demonstration for physics class. (I'm a week ahead of my normal pace; I have a spare week to cover extra material).
 
Originally posted by: MrDudeMan
Originally posted by: phisrow
Thanks for the suggestions, guys. I picked up a propane torch this afternoon and made a few attempts.

My best results are still only a few millimeters in size; but they do actually work, which makes the whole project rather exciting.
Click to expand...

good job. post some pictures if you get a chance. i'd like to see what you've created.
Click to expand...

This and this are pictures of my best result so far. This one was done from a small bicolored soda-lime glass rod. The bulb end is ~1cm in diameter. As the drops get larger, their stability seems to decrease. Of the other 6 attempts from that rod, one shattered spontaneously about 10 minutes after cooling(spraying glass fragments all over my desk) and the remainder shattered 20 seconds to 3 minutes into the cooling process.

I'm still trying for a transparent one, so that I can photograph the internal stress patterns; but I've not had luck with clear glass as yet.
 
Arn't these glass slivers dangerous? I know when punched through the window accidentally it took me 3 hours to take out all the splinters.
 
Originally posted by: Talcite
Arn't these glass slivers dangerous? I know when punched through the window accidentally it took me 3 hours to take out all the splinters.
Click to expand...

They don't break that way. They leave behind pulverized glass, more a powder than shards. They are also rather small.
 
This is pretty awesome. I might have to try it.

So could you go to home depot, get an oxypropane torch, and do it with borosilicate? There's at least one cheaper model of bernzomatic torch that does oxypropane (two separate tanks), and I've definitely used it to melt copper for instance.
 
Originally posted by: sjwaste
This is pretty awesome. I might have to try it.

So could you go to home depot, get an oxypropane torch, and do it with borosilicate? There's at least one cheaper model of bernzomatic torch that does oxypropane (two separate tanks), and I've definitely used it to melt copper for instance.
Click to expand...

You wouldn't want to use borosilicate. The effect only works because of the intense internal stresses that come from soda-lime glass' relatively high coefficient of expansion. Borosilicate glass would be much more reliable; but it would only produce simple teardrop shapes, not Prince Rupert's Drops.
 
Originally posted by: phisrow
Originally posted by: sjwaste
This is pretty awesome. I might have to try it.

So could you go to home depot, get an oxypropane torch, and do it with borosilicate? There's at least one cheaper model of bernzomatic torch that does oxypropane (two separate tanks), and I've definitely used it to melt copper for instance.
Click to expand...

You wouldn't want to use borosilicate. The effect only works because of the intense internal stresses that come from soda-lime glass' relatively high coefficient of expansion. Borosilicate glass would be much more reliable; but it would only produce simple teardrop shapes, not Prince Rupert's Drops.
Click to expand...
I've seen tear-shaped borosilicate glass (pyrex) that was pretty resistant to striking, but that shattered to dust when the tail got broken.
 
Interesting. I've made a sculpture out of lead, by melting lead in a cast iron post, and then pouring it into a soda can that was filled with water. The cooling process made the liquid lead bubble and everything, making a very interesting sculpture. Sadly, I have no idea what happened to it, which is kinda scary, because that was quite a bit of lead...
 
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