A dammar formulation is given which should not significantly yellow in two to three hundred years of natural ageing. It is also shown that the choice of solvent when preparing a dammar varnish solution will affect yellowing rates of the resulting films. The recipe given is: 20% solution of dammar in a suitable solvent as cyclo-sol 53, xylene or toluene to which 1% irganox 565 (wt/ wt of resin) is added.