Thank you for commenting. When I finish a painting I will apply a temporary retouch varnish of Dammar resin. For the final varnish I will wait at a year to ensure that there is no problems.
Modern Dammar Retouch varnishes are much better than traditional Sandarac varnishes. I explore the subject of traditional varnishes in this video. ru-vid.comqepKLC6XrOg?si=aX6_bReoGN3ndY9n