This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
(a) 1 lb. American pearlash, 3 lb. quick stone lime; slake the lime in water, then add the pearlash, and make the whole about the consistence of paint. Apply it to both sides of the glass, and let it remain for 12 hours, when the putty will be so softened that the glass may be taken out of the frame with the greatest facility. (b) A correspondent of the Garden says: - After many trials, and with a variety of differently shaped tools with various success, I at last accomplished my end by the simple application of heat. My first experiment was with a soldering iron, when I found the putty become so soft that the broken glass could bo removed by the fingers and the putty be easily scraped away. All that is required is a block of iron about 2 1/2 in. long by 1 1/2 in. square, flat at the bottom, and drawn out for a handle, with a wooden end like a soldering iron. When hot (not red) place this iron against the putty or fiat on the broken glass, if any, and pass it slowly round the sides of the square. The heat will so soften the putty that it will come away from the wood without difficulty.
Some of it may be so hard as to require a second application of the hot iron, but one experiment will give sufficient instruction to meet all difficulties.