stopverfPutty (or mastic, glazing compound) is a stiff dough of powdered chalk, white lead (poisonous, white lead pigment, is no longer used) and linseed oil or soybean oil. It dries very slowly, over several weeks or more preferably months. It is used to fasten panes in a window.

The resin of the mastic tree Pistacia lentiscus was mixed with a filler used as putty.
The window is cut a few millimeters clearance (too small) and fixed firmly with nails (or glass pens). Works with putty seal finishes everything.

Too weak (fresh) putty you can strengthen with chalk. Too stiff putty you can make smooth by heating them in your hands and knead, possibly with some linseed oil.

Dry putty you can heat to make it soft, or chop it with a chisel.