HELMUT RUHEMANN'S INPAINTING TECHNIQUES
7 INPAINTING MEDIA
The inpainting medium should look and behave like the original medium, but must not darken with age.
For tempera paintings I still like to use egg tempera, yoke and white, with a little additive of wax for elasticity and a wetting agent like ox gall. Some very smoothly painted tempera surfaces are better imitated in egg white and wetting agent leaving out the yoke and wax. The great disadvantage of tempera as a medium is that it darkens considerably in varnishing, some pigments more than others, so that its use needs a great deal of experience. The paint has to be applied, dried with a hair drier, burnished with an agate, and tested with a little mineral spirits to see whether it will match the original color when varnished.
For inpainting oil paintings, I find that Paraloid B72 imitates the translucency of the original paint better than any other medium I know. As the technique and the quality of an oil painting depends largely on the fact that oil paint is translucent, it is important not to inpaint in a more covering medium than oil in the design layer. For the ground color a covering medium like resin MS2A is useful.
Egg tempera and Paraloid B72 are the most successful media for imitating the painter's brushstrokes. I use watercolor for the very fine, sharp raised brushstrokes in areas such as the hair or the blades of grass in early paintings. But it must be remembered that watercolor also darkens when varnished.