Stained glass window putty is used in lead-jointed windows to help seal the window against the weather, protect the glass from rattling and to strengthen the window. There are a variety of recipes, but the basic ingredients are the same. The consistency is a matter of personal preference, but should be firm enough that it can be squished under the edges of the lead.
Measure the boiled and raw linseed oil in equal parts into the bucket.
Mix in the whiting a cup at a time. If you used 118 ml (1/2 cup) each of boiled and raw linseed oil, use up to 800 g (4 cups) of whiting, possibly a bit more, depending on the consistency you prefer to work with.
Mix in about 1 tbsp of the stove or lamp black, depending on how dark you want the putty.
Mix everything together until there are no streaks. Use your gloved hands when it gets difficult to mix with the spoon. The consistency can vary, but peanut butter is a close comparison.
Recipes that use plaster of Paris or cement are not recommended because the product is too hard and stiff when dry, providing no cushioning for the glass inside the lead frame. A slight rubberiness is desirable to provide support without the stiff restraint of the cement, which can cause the glass to break.