pdennis -- If you want to try the glass/oven method, use 3/8" thick glass. 1/4" may not provide enough even weight, and 1/2" may not heat and cool evenly. You should also observe the following:
1.) Make sure your oven really goes down to 140 degrees. Many don't. Test it with an accurate thermometer first.
2.) Believe it or not, gas ovens are better (more even heat inside the oven chamber.) If you only have an electric oven, place a large broiler or baking pan on the lowest rack position right over the heating element to avoid direct heating of the lower piece of glass.
3.) Wait until the oven has remained at the desired temperature for a half hour or so to insure even heating. And then place the record/glass sandwich on the middle rack.
4.) For cool-down, don't move anything. Just turn off the oven and crack the door open until everything reaches room temp.
