[John-Paul Stonard]

I would like to know what the physical change could be expected if Silver Nitrate was combined with dammar varnish and exposed to natural light. Am I right in assuming that over time it would slowly darken?

[Borek]

I had to check what dammar varnish is.

Hard to say. IMHO it may happen the mixture will change color immediately. The only sure way of knowing is to make a test.

[Arkcon]

It sounds like an interesting project, I wonder if the darkening you'd get would be aesthetically pleasing or not.  I suppose it would depend on how much silver nitrate was mixed with the varnish.  However, I can't help but wonder how well you can disperse an ionic silver salt in a mixture of triterpenoids and turpentine, nonpolar substances all.  If you're just looking for a suspension, then there are a variety of silver salts to try.

[John-Paul Stonard]

Thanks for these answers. Testing seems sensible. The question relates to a painting by the artist Sigmar Polke, and I can confirm that the results are aesthetically successful!

[Arkcon]

The Wikipedia article and one of the references on Wikipedia don't seem to provide details on what sort of reactions Sigmar Polke was using.  If you have a specific reference, I'd follow it, otherwise, you can keep trying what you've come up with.  Anyway, thank you for sharing this topic.