Varnish crackle effects

An easy approach to varnish crackle and faux crackle techniques that could be applied to restoration and antiquing

TRADE SECRETS Makers reveal their special techniques

ALL PHOTOS PABLO ALFARO

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.

Using One Step Crackle

1 When varnishing a new instrument, I first apply several layers of spirit varnish. Before the last layer dries I apply a coat of One Step Crackle with a small brush, and let it dry for about 20 minutes. If I am retouching the varnish on a repair project, I apply a couple of coats of clear spirit varnish to the area where the crackle effect is needed. Before the last coat dries I apply a coat of One Step Crackle and let it dry. The more product I apply, the bigger the crackle effect.

Applying acrylic

2 Once the product has completely dried, I apply a small amount of acrylic pigment to the crackle, which will simulate patina on the instrument. I can use burnt umber or black, or a combination of colours such as greens and greys, depending on what I need. I let the pigment dry for ten minutes, then clean off any extra pigment with a damp, but not wet, paper towel. Not every single crackle effect needs to be filled with ‘patina’.I can easily control the amount of pigment by repeating the cleaning process two or three times. At this point I let everything dry completely.

Protecting the effect

3 Once the acrylic is fully dried, I apply some more layers of clear varnish to protect the effect. In restoration, the clear varnish has to match the texture, transparency, reflection and refraction of the original one. It doesn’t take long for these few layers to dry.

Crackle effect with no pigment

4 Some instruments require a crackle effect without any patina.In those cases I apply a couple of layers of clear spirit varnish to the area where the crackle effect is needed, and before the last layer dries I apply a coat of One Step Crackle. If I need a very small crackle effect, I only apply a thin layer of the product. Again, once the acrylic is fully dried I apply some layers of clear varnish to protect the effect.

a Creating crackle with an X-ACTO knife…

b …with a pencil…

c …and a Micron 01 Sharpie

5 If I need to copy a specific crackle pattern, for example when making an exact copy of an instrument, it has to be done by hand. After all the layers of varnish have fully dried I use an X-ACTO knife (5a), watercolour pencil (5b) or a Micron 01 Sharpie (5c) to draw whatever crackle patterns I need. This method works for both spirit and oil varnish.

a Marks added with a knife

b The marks filled with patina

c Crackle effect achieved with a watercolour pencil

6 I can draw lines with my knife to create any desired pattern or a specific crackle effect. The thickness of the knife will also determine the texture of the effect. I also have the option of doing it with or without patina. As shown in previous steps, I always apply some layers of clear varnish to protect the effects afterwards. If I use the watercolour pencil or Sharpie options, obviously the effect will be totally visible.