An interest of mine which I am trying to turn into a hobby is building miniature steam engines out of brass. So far, I'm a good way away from a working engine, but I decided to post a quick mini-Instructable about a tool that I built to make my life easier. It seems a bit obvious to me, but it is useful, so here it is.
Specifically, I needed a high heat work surface to protect the shiny new Formica that I recently added to my workbench from the heat of the mini-torch that I use when soldering brass. I will probably also end up using it as a general-purpose work surface for electronics soldering and rework, although as these applications are much less demanding, I have been using the steel base plate from my Desk Squid until now.
Step 1: Building the Surface.
I started by buying a 12"x12" white ceramic tile from Home Depot for about $1. Being made of kiln-fired ceramic, this tile should be a perfect refractory material. Still, there were a few things that concerned me:
1) Ceramic tile is very hard and has a rough bottom. This isn't good for my bench.
2) Ceramic tile is brittle. Under spot heating, it may even crack.
3) Many ceramics are actually rather good heat conductors. While I have not done a thermal gradient analysis on this tile, if it turns out to conduct heat, then this would reduce the problem of #2, while allowing the bottom of the tile to reach a temperature that may be uncomfortable for my bench.
The answer to all these problems, as I see it, is cork. Cork is an extremely effective thermal insulator, and it does not melt. To destroy cork requires igniting and burning it off, which is a slow process. It is also soft, and won't scratch my bench. If the tile should crack, the cork will give my desk protection long enough for me to remove the heat source.
I bought a couple $1 cork boards from the Dollar Store. They came with some plush heads stuck to them with hot glue, which I removed with my hot air rework station, set to about 250°C and maximum air flow. Cork is difficult to cut with an Exacto knife, so I used the rotary cutter from my sewing room to cut it down to shape. You may be able to find cork in appropriate sizes already cut; a few days after I built this, I saw some 12"x12" cork squares for a couple dollars at Walmart.
I glued the cork to the back of the tile with rubber cement, and put 100lbs of stuff on top of it overnight to let it set. It seems to have held well enough, but I suspect that it may fail under thermal stress, as rubber cement is not known for its temperature stability. Both materials are very porous, so they take adhesives quite well, but the back of the tile is uneven, so it requires a space-filling adhesive. If I had to do it again, I would use a two-part epoxy. Epoxy generally survives high temperatures well, and it bonds strong.