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Using Propane Torch For Glazing


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#1 revolutionaryspirits

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Posted 23 February 2014 - 08:03 PM

I'm a novice to pottery.  Has anyone ever used a torch to glaze things, instead of putting them in a kiln?  Propane and butane torches reach temps of about 2500 degrees.  Any advice would be welcome.  Thanks.  



#2 Chris Campbell

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Posted 23 February 2014 - 08:11 PM

In theory this may sound like a plan ... But there are things working against you.
Mostly that the torch only heats a small area and how would you know what temp it was at and for how long?
How would you get the whole thing looking the same?
Torches are great for bumping up raku pieces, cleaning white crackle and such ... But doing a whole piece means you have to stand around doing each piece. Not repeatable or cost effective.

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#3 JBaymore

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Posted 23 February 2014 - 08:38 PM

I've seen people use it to fire overglaze enamels in localized areas as well as resin based lusters. But that is surface treatments on already fired work and small areas. And it is VEEEEEERY difficult to do , because of the thermal shock issues of heating one area and not the whole form. More of a "tricK' than a useful tool in this regard.

 

For still HOT raku work and localized reoxidation.... a great tool. Started doing that with my classes at Massart back in the 70's.

 

For demonstrations in my kiln design and operation classes, I've used a plumbers propane torch and an enclosure of insulating firebrick (very small) to show how simple a kiln can actually be.  The chamber has to be very tiny for the BTU output of the torch and the total fuel store available in the tank.  But it works.

 

best,

 

...................john


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#4 Surubee

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Posted 23 February 2014 - 08:39 PM

Another problem with using a propane torch to fire something is uneven heating. The spots where the torch hits can get very hot, but other parts of the piece are considerably cooler.  The thermo-shock between the hot and cool spots are very likely to lead to cracking as the clay goes through major changes when the chemically bound water in the clay body is released and when the quartz in the ware changes composition when heated.

If you are using the torch to heat a chamber with the ware inside (like a small kiln) so that the atmosphere and bricks are heated as well,  that is an entirely different situation and may work. 

As always, your situation may vary. Test, test, test. 



#5 Marcia Selsor

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Posted 23 February 2014 - 10:26 PM

I have used a torch to flash iron sulphate wash on terra cotta. I have seen a torch used to make patterns on raku glazes post firing. but I have nave seen a glaze melt using a torch. As Surubee says, the uneven heat would be more likely to crack a piece. a torch is just a tiny burner unable to surround the piece.
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#6 Colby Charpentier

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Posted 23 February 2014 - 11:42 PM

Propane will actually burn somewhere around 3500 degrees in the primary flame, the closest thing that I've done to firing with a torch alone is firing a small kiln, 6" max interior dimension, with a small torch. It requires a small throat just to make sure the torch doesn't directly contact any of the work....



#7 jrgpots

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Posted 24 February 2014 - 12:03 AM

I use a torch to see how easily raw material or clay melts. It gives me a rough idea of melting points based on color glow. I collect a lot of rock material. When i get new material, I melt a small section of the rock to see color of the melted material. I am still amazed how a piece of red feldspar can melt giving a beautiful white glossy glass with black specks.


That being said, the uneven heat causes thermal shock with lots of cracks and explosions.

It's fun to heat iron pyrite. It explodes. So does jasper.

Just a bit of FYI,

Jed

#8 Marcia Selsor

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Posted 24 February 2014 - 08:06 AM

Propane will actually burn somewhere around 3500 degrees in the primary flame, the closest thing that I've done to firing with a torch alone is firing a small kiln, 6" max interior dimension, with a small torch. It requires a small throat just to make sure the torch doesn't directly contact any of the work....

Ahhh but the original question says fire with a torch INSTEAD of putting them in a kiln. This is different.
Marcia




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