6 FILLING

Filling is boring and difficult, but it is essential to get it right for the success of invisible inpainting.

After many years of experimenting I still come back to Helmut Ruhemann's putty as the best filler. It has a smooth texture, clings well, does not shrink or expand, and can be easily removed.

The following is a satisfactory formula:-

• 60 grams gilders whiting
• 15 grams stand oil
• 20 grams animal glue in water, rather viscous
• 10 grams zinc white
• 5 grams bees wax

Combine all ingredients on a hotplate warm enough to melt the wax, and knead together to a smooth consistency.

Before filling a damage it is advisable to varnish the painting to prevent hair cracks from inadvertently filling with putty. Apply the putty to the hole with a small spatula, then use a small flat piece of balsa wood to push it home. Moisten the balsa wood slightly, and with circular motions wipe the surface of the filler flat and flush with the paint surface. In this way the putty fills the hole and finds the right surface more or less automatically. Where necessary, imprint canvas grain at this stage with a matching canvas grainer made of a thin layer of a resin which sets hard without losing all flexibility on fiberglass cloth.

Allow the putty to dry, and then scrape with a scalpel until the edges of the damage appear sharp and the surface is smooth. The surface should be slightly lower than that of the surrounding paint to allow for the thickness of the inpainting.

Insulate the surface of the filling with a thin coat of shellac, taking the greatest care not to go beyond the edges of the damage. Finally, where there is putty over the original paint, wipe it off with mineral spirit.