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Heatproof jigs, not a soldering question, but one which people with soldering experience are best equipped to answer

I’m seeking advice on how to set up a heat proof jig for working with a torch and glass .

The aim is to heat the sharp sides of glass squares and rectangles to the point that they round off, and are capable of being handled safely by the end user.

I know that this rounding can be accomplished with even the plumbers’ torches that are available in hardware stores, but the trick is to hold several in place at once in order to work efficiently.

What is envisioned is something that is perhaps 2 feet long that, in cross section, , looks something like a squared off U, with the vertical sides close enough together to hold the pieces upright while I move the torch swiftly and continuously enough to melt the edges while avoiding slumping the whole piece(s). .

What I’m seeking is a material that 1) will not burn or give off fumes, 2) will not act as a heat sink, thereby prolonging the process, 3) is sturdy enough that the jig will hold up under extensive use, and 4) poses few, ideally no, health risks to the user in regular contact with hit , and 5) will not adhere to the glass as a result of the higher temperatures involved.

I recall a long time ago in Jewelry class we used drop ceiling tiles for soldering, and these served that function admirably. Earlier today, I stopped by Home Depot to look at their ceiling tiles, but unfortunately those are no longer put out as singles, so I was not able to examine them. I did come home to do some research, and discover that the Rader R2413 is firecode rated for what ever that is worth. I can’t find out how it fits with the other criteria, however

A friend has suggested using graphite blocks, and while that would seem to fit all the criteria, it is also somewhat expensive, so I’m hoping that someone here can come up with an alternative .

Thank you for your time and attention.

Jim –
You don’t say what size glass pieces you are using but perhaps you could cut strips from Solderite boards and fasten them to something like 1/2" or 5/8" square mild steel bar with flat head screws to form “angles” to support your glass. The Solderite is pretty rigid and well tolerant of high temps. I don’t know if the glass would stick to it if it melted but it seems like it would be better in that regard than metal. The Solderite board is available in 6x6, 6x12 and 12x12 inch sizes from Rio (and, i’m sure, from other suppliers.)
Another material that might work is tile backer board (e.g. “Hardy Board.”) You can get it in various thicknesses from 1/4" to maybe 1/2" from a builders supply (and, it would be cheaper than Solderite board.)
You can cut either product with any blade that will cut masonry.
If you need clamping force then maybe bend flat (or round) steel bar into ‘hairpin’ shapes that you could slip onto the ends of the ‘angles.’
– alonzo

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First thought was the ceramic honeycomb soldering blocks. Rio’s description is that it dissipate heat from work while another site states it reflects heat.
T pins can be placed in openings. Takes temps up to 2000F - also sometimes arrives broken according to reviews.
HTH

Jim - depending on the size of the glass squares, tumbling does a great job of softening edges and corners of glass. And if they are too big, I’d think that a belt sander would be an alternative.
Judy Hoch

Look at tile backer. I don’t solder on it, but I use it as a heat shield. It is fairly inexpensive and can be cut the same way that you cut drywall. You should review the msds first…Rob

Jim, I would hesitate to flame polish or heat glass edges to soften the edge unless it is a borosilicate glass. Regular soda glass has a high coefficient of expansion and develops significant internal stresses than can spontaneously break weeks later unless properly annealed. One thing enamelists and hot glass workers use is a mica sheet to support the glass and prevent sticking.
I wonder if kiln wool would fuse to the glass, or if it could be used to provide support. There are also some very high temp ceramic sprays that hot glass folks use to prevent sticking, but they seem to dull the glass.

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Hi Marlin,

Thank you for your reply.

I was aware that internal; stress could be a factor, but had thought/hoped that since I was only working the edges it would not be a problem.

I did find a source for borosilicate, and while it is somewhat more expensive, figured that it would still be viable.

However, from what I’ve seen so far, it also seems that it would require a much higher temperature to melt-round the edges, and a plumber’s torch or even a jewelers propane torch, which I also have available to me, would not be a viable solution…

I guess I’m going to have to put some more thought into this.

By the way, from what I understand, I will need to wear welders’ glasses when taking any kind o torch to glass. Is that correct?

Thank you,

Jim

Hi Judy,

Thank you for your input.

I would mostly be working with 2" x 2", sometimes 2 x 3" or 1 1/2 x 3". I’d be concerned that tumbling might dull the class, which I need to be clear,

I have considered a belt sander, and use one for a different process. I would would be concerned about possible health issues with minuscule glass particles flying aropund, even though I have a very effective particle respirator.

Could you speak to that?

Sincerely,

Jim Benson

Speaking to the belt sander issue:
the glass should be sanded wet. Of course the mist is still a hazard.

It would be best to use finer grits for the process as the glass may develop internal stresses if there is “chatter” against the belt. Try a worn belt to start - 600 or finer.
It helps to practice a bit to find a touch and angle that keeps the glass in smooth contact with the belt to avoid hopping or skidding.

Jim - you are correct, tumbling will dull the glass. The only option I can offer is to design for a matt finish if you need to tumble.
An alternative would be to specify cast glass. Then you can have whatever edge configuration your design requires. More expensive up front but without all the finishing on the back end. Depending on your volume, talk to a glass artist that either casts or fuses.
Judy H

Maybe use a glass grinder, used by stained glass artists?
For example:

You can easily work borosilicate glass with propane (I used natural gas when I taught chemistry, and it was fine) and a jewelers torch should do the job. If you move up to fused silica, you will need more heat. You do not need welders goggles to work glass, although Didymium eyeglasses are fantastic. They specifically cut the light at the wave length of sodium (the yellow flare obscures your work without them). They also cut the UV and a few will attenuate the IR. I have a pair of ill-fitting Didymium glasses I use sometimes, they have a slight lavender tint, but are very clear otherwise. I second the notion of using stai glass grinders designed to round the edges of glass, although the ones I have always left a very matt finish. They are designed with water to cool the operation and partially contain the silica dust, although I always seem to get splatter around.
Another approach would be to sand blast the edge. Harbor Freight has some inexpensive cabinets and blasters assuming you have a good compressor. You would need to mask the areas that you do not want to remove - that might also work with tumbling. This would still leave a matt finish, but perhaps you could use the lapidary techniques to do a quick polish with something like cerium oxide. My first step would be to go to a large stain glass store that also sells hot working tools and pick their brain
Marlin

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I use these with water. They won’t give a glass finish but they break the edges nice.