High all, I'm new to this whole hobby, I have a rather oddball question.
Background: Fused silica happens to be the ideal substrate for making telescope mirrors. It is basically just pure sand melted at about 2000 degrees C. As a result they are really expensive. While I don't anticipate being able to actually melt enough for a telescope mirror, I've been wanting to see if it is possible to melt a smaller (1cm x 1cm) amount in a solar powered "forge", using a big parabolic mirror. Just for the fun of it, no good reason really. Just to see if it is possible.
I've got a mirror design to try, and I'm thinking the "forge" will be best made like a smaller version of the "backyard coffee can forge" I've seen floating around, probably using a couple of soup cans instead. I'll have a nice small hole in one end to pour the sunlight in. However there are a couple of things I haven't yet figured out, I was wondering if you would have any ideas.
1. At 2000C, I estimate 93% of the energy lost from the target sand is given off as IR radiation. In order to maximize the amount of energy that stays in the sand, I would like to line the inside of my soup can with something that will reflect as much of that IR light back onto the sample as possible. My first thought was a sheet of aluminum foil, but I'm afraid that might melt. Do you know of anything else you guys line your forges with that reflects most of the IR and won't melt? I suppose ideally the liner would never reach nearly the same temperature as the glass, but I don't know if that's possible.
2. I'd like to be able to track and measure the temperature inside the forge to check my progress and see how close I am to the goal of 2000, but I'm having trouble finding any thermocouple's/pyrometers that will go up to 2000C. It seems most of the one's I'm finding top out around 1300-1500C, beyond which I assume they start melting. Any ideas for higher temp versions? (preferably cheap). Should I look into going contactless instead, like a laser thermometer?
Thanks for any ideas, cheers!
-- Keegan
