Repairing an old beveled glass panel
When worked with old glass bevels, one of the first things you notice is a significant difference in color and thickness of the old glass. This is due to the "recipe" of the glass which has varied over the years. Before the mid 1950's, when the modern blue-green colored "float glass" was invented, the glass had a more greenish tint, and as you get back to the turn of the century, and earlier, the glass had a yellowish or yellow-green tint.
In this photo of two beveled glue chip pieces, one can really see the difference between old and new glass. The piece on the left is about 100 years old, and the one on the right is new.
When restoring a panel of this vintage using a new piece of glass, the new piece will stand out and be obvious. The piece will be the wrong color, and too clean and perfect, and the panel will look "repaired".
For this reason, I have, over the years, been salvaging any old glass I can find. If someone is repairing and older panel, I want to be able, when possible, to match the color, thickness, and even the bevel angle of the original piece as closely as I can. Even the very condition of the glass, be it scratched, or stained, or hazy is important in making the repair look as original as possible. A little extra effort goes a long way.