ketone resin
Polycyclohexanone is a crystal-clear synthetic resin that can be dissolved in mineral spirits to produce a rapid-drying varnish that is resistant to yellowing in UV (though it tends toward yellowing in the absence of light); however these synthetic resins, such as Laropal, tend to be more brittle and risk oxidation over time that results in the need for aggressive polar solvent mixtures to remove. (Preservation Science, 2019)