Q. I’ve been tempted by ads for amber mediums that promise to protect oil paintings far into the future without varnishing, in addition to adding luminosity and depth. But these mediums are quite expensive, so can I trust these claims, and are there any disadvantages to using amber?
A. Amber, a resin made from fossils, has been a traditional additive to oil painting mediums because it gives a pleasing, yellowish-brown tone to the paint. So in that respect, like many mediums, it can add the appearance of luminosity to your work. It cannot, however, protect the painting from damage or deterioration because it doesn’t coat the surface like a varnish does. Also, like many traditional natural additives to oil paints, amber has the disadvantage of darkening as it oxidizes. In short, I’d view those marketing claims with some skepticism.
If you want to use a medium in the latter stages of an oil painting, I recommend you try one of the modern alkyd painting mediums for oils: Galkyd, made by Gamblin, or Liquin, made by Winsor & Newton. These mediums can be found in light or heavy viscosities to suit your application needs, they won’t turn yellow, and they have the advantage of drying rather quickly. Another option would be to try a medium based on linseed stand oil or Venice turpentine, but these, like amber, have the disadvantage of eventual yellowing, and they don’t dry as quickly as the alkyd mediums.
As for protecting the painting, you ought to reconsider varnishing. A varnish layer will be a barrier to dirt, dust and other material deposits on the surface of the picture that would otherwise embed themselves in the paint layers, and when the time comes to clean the painting, in 20 years or so, you’ll find it far easier if the painting is varnished. A proper varnish coating will also improve the color relationships in a painting, and it can even add the luminosity and depth you’re looking for.