Capital City Carvers

A Spotlight on Spalted Wood, Dr. Sara C. Robinson, Woodcraft Magazine, June/July 2014

An article in this issue of Woodcraft Magazine caught my eye and I thought I would share it with you. Some woodworkers claim that spalting is caused by bacteria, others think fungus is the causal agent. Scientists have been studying and researching the causal mechanisms behind wood decay. Spalting is caused by very specific fungi with very specific goals. A wide range of basidiomycete (wood decay, specifically, white rot) fungi and a very small number of ascomycete fungi are responsible for spalting. Most airborne molds don't spalt.

Below the bark, you'll find three categories of spalt: The first, "bleaching," lightens the wood and causes strength loss (referred to as punk). The second signature category is called zone lines, often black but sometimes red, green, pink, yellow, and brown. These scroll across wood and serve as a boundary for one fungus to protect its resources from another. The third, pigmentation, displays bright colors inside wood. These are commonly pink, green, or blue, although other colors exist.

The earliest uses of spalted wood trace back to 14th century Italy where green spalted wood showed up in inlaid intarsia works. Today woodworkers choose spalted wood for door panels, box tops, knife scales, and turnings. In other words, it is sought for its decorative-not structural-qualities.

One could find spalted wood by checking out any woodpile or logs lying on the forest floor. Of course, you can purchase spalted wood from woodworking supply retailers or online. Species for carvings include buckeye, sycamore, apple, basswood, and holly. If some areas of the wood appear too punky, stabilization with thin CA glue or shellac is useful.

Safety concerns abound in the literature about working with spalted wood. It is highly unlikely that there are fungal spores inside wood. Spores live on the surface, if they exist at all, and not all fungi produce spores all the time. If you have a spore fear, spray your wood with 91% isopropyl alcohol (available at drug stores). Beyond that, careful woodworkers know they need to wear respiratory protection when working with any wood. That's because wood dust can cause allergic sensitivity and even cancer. If you are wearing (as you should be) a NIOSH 95 or better mask, you are blocking whatever spores may exist and protecting against mold as well. Standard cutters should work fine when machining spalted wood, but avoid running suspect spalted boards through the jointer, planer, or tablesaw. When sanding, ALWAYS wear a mask and avoid spreading the dust to others.

Painting Ditties

When painting your carvings, sometimes you need to mix colors to get the shade you want. Here are a few tips from the Cheap Joe art catalog.

Which Black?
    Ivory Black - Has a warm brownish undertone and low tinting strength. A great black for mixing with other colors.
    Lamp Black - Has a cooler blueish undertone and a higher tinting strength than Ivory Black.
    Mars Black - The most opaque black. Perfect when large areas of black are needed.

Which White?
    Mixing White - Perfect for use with tinting. Helps prevent chalkiness.
    Titanium White - The most popular and opaque of whites. Highest tinting strength.
    Zinc White - Most transparent white, perfect for toning down color. Lower tinting strength.
    Iridescent White - White with pearl effects.