Trade Secrets: Varnish crackle effects

Varnish crackle occurs when coats of varnish have dried unevenly, such as when some of the lower layers have dried more slowly than the external ones. It can also occur as a result of wood deformation, or if the instrument has been exposed to extreme heat. As a violin maker who likes to antique instruments, I have found several ways to create a crackle effect. Probably the most difficult part of the process is retaining control of the final look.

Some time ago I discovered a product called One Step Crackle, which works well with spirit varnish. Made by DecoArt, it has a similar effect to protein- and water-based solutions such as hide glue, gum Arabic and egg white, but with the advantage that no hairdryer is needed. As a general rule, spirit varnish is used for varnish retouching in repair and restoration work.

A different way to create the crackle effect is simply to draw on the fully dried varnish using an X-ACTO craft knife. A third method that creates a very nice, controlled crackle effect is by drawing on a fully dried varnish using watercolour pencils or a brown Sharpie, and protecting the effect with more clear varnish…