Ceramic blanket for silver soldering source

Stumpy, This link: http://www.clay-king.com/kilns/kiln_accessories/kiln_brick_and_kaowool_blanket.html shows the right ceramic blanket. 4.08 square foot, two square foot minimum. Two square feet would be more than enough. Any pottery supplier should have this stuff or its equivalent. Be aware that this stuff does shed fibers that, like fiberglass and rock wool, are bad to breath. When I use mine I wear a mask and gloves. Just a cheapie disposable mask. If handled with a little care the stuff is easy to re-use. I keep mine in a plastic garbage bag. When I need to make a little oven lots of the time I can get away with laying the stuff on the welding table, laying the part on the kaowool, and forming the kaowool around the part, leaving the top open enough to apply the heat. The part you are going to solder may be small enough that you can just lay it on an insulating surface and go to town. I have found that Hardi Backer Board, made for wet locations like showers and for hot locations like around a fireplace insert in new construction, makes an excellent silver soldering pad. I had some left over from when my house was built. I don't mean greenboard. I wonder if your home improvement center might have a damaged sheet they would sell for cheap. Eric

On 07/02/13 01:42, snipped-for-privacy@whidbey.com wrote:
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http://www.clay-king.com/kilns/kiln_accessories/kiln_brick_and_kaowool_blanket.html
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I haven't tried that "wrap it up in a blanket" technique - personally I do not like to use kaowool in anything other than a fixed enclosure, especially since I gave up smoking and moved out of the city (though there is a safer "soluble" type which dissolves in the lungs rather than stick around and irritate them). Must give it a try sometime though.
However on the same page in the link you will find k23 insulating firebricks. These are very soft - you can crumble them in strong fingers, and a hacksaw blade will cut them very easily.
They are perfect for making a small brazing hearth, where the work is surrounded on as many sides as you can manage - don't forget a lid, even a partial lid makes a big difference. They reflect the heat radiated by the part back, and also reflect the heat from the flame which misses the part and hits the bricks, and make it much easier to get to and maintain the right temperature.
You will probably need two bricks for a hearth for something the size of a derringer - you can cut them in 2 or 3 lengthwise to make slabs about 3/4" thick.
It is fairly usual to heat the hearth for a bit before heating the parts - a couple of minutes will do if using insulating firebrick.
[ If non-insulating firebrick is used and the hearth is to be used occasionally, some people leave the gas on the hearth all day to let the heat soak into the firebricks. Not needed when using insulating bricks though ]
-- Peter Fairbrother

On Thu, 07 Feb 2013 02:23:55 +0000, Peter Fairbrother
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Greetings Peter, I quit a long time ago and try to limit my exposure to bad stuff for lungs too. That's why I wear a mask when using the blanket. It does pay off to use the stuff sometimes. Eric

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http://www.clay-king.com/kilns/kiln_accessories/kiln_brick_and_kaowool_blanket.html
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I have some Hardie Backer Board already. A 3' x 5' sheet to keep the dog from climbing over a low side wall. I'll replace it with some plywood and then can make my little grotto/hearth and line it with some of the stuff you mentioned. I don't want to get too sophisticated before I've even made my first attempt.

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Absolutely right. If it was me I would just lay the practice piece, which should represent the real piece in size and weight and material, on the Hardi stuff and see if it works. If not then cut some pieces off to make the little oven and try again. Eric

On 2/6/2013 11:02 PM, Stumpy wrote:
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That might not be a good idea. Hardie backer board is basically mortar/concrete and concrete can spall, violently, when heated too high. Try heating a small spot first. Bob

On Fri, 08 Feb 2013 08:26:23 -0500, Bob Engelhardt
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Greetings Bob, I did try heating the backer board with my air/acetylene torch, expecting spalling. But maybe because it's so thin, or the air was dry, but I have used the stuff several times for silver soldering and for a heat shield when soft soldering copper pipe and it has never spalled. Of course, my experience does in no way guarantee that someone else wouldn't experience spalling or worse. My sample size is too small. Eric

On 2/8/2013 11:57 AM, snipped-for-privacy@whidbey.com wrote:
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Eric - your sample size is many, many times larger than mine <G>. It's good to know that you were able to use it without problems, thanks. Bob

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That book came in. I'll try to slow down and learn something before I get to work.

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Sounds wise. The board has been out in the weather for ~12 years and it's been raining alot recently.