Before I go into this post about spalted wood I want to be sure that this is not interpreted as being smarter or a better woodworker than anyone else. Quite the contrary. Most of what I know about wood comes from doing things wrong. Since I work with wood 7 days a week I have utilized my opportunity to ruin quite a bit of really good wood. Eventually I catch on with things that occur regularly.
Spalted wood is wood that has started to decompose and has become inhabited by colonies of fungus. The fungus is what causes the atypical coloring. When 2 or more colonies of fungus come in contact with each other a black line will occur. This is a barrier between the colonies.
The further the spalting progresses, the more dramatic the random coloring and the further along the decomposition of the wood.
The wood will progress from slightly softer, to cork like, to crumbly when it has gone too far. Spalted wood to be stabilized is usually in the cork like stage. This is the time when the coloring is at it's peak and the wood still maintains a degree of structural integrity. This is the time when the wood is easiest to stabilize. Even by the do it yourselfers. The wood in this form easily accepts the stabilizing solution much like a dry sponge placed in a bowl of water.
The way stabilizing works is a stabilizing solution is used to impregnate the wood in a tank that is placed under a vacuum and pressure. After the wood is completely impregnated it is then heat cured causing the solution to catylize and become a solid. Properly done the solution will penetrate the fibers and pores of the wood giving it enhanced hardness and durability.
Stabilizing does not replace the wood so it is still subject to the original structural integrity. It has just been enhanced in multiples.
Even when stabilized, the 2 weakest woods will be heavily spalted pieces and end grain pieces. If you take either one of these types of wood at about 1 inch thick and attempt to break them in half, they will. If they don't, it just means you weren't trying hard enough.
With all this said, people might say "then why use the stuff?".
Answer: because it looks so good.
For those who insist upon using woods like this special care must be taken. Construction should be in a manner that would not subject the wood to flexing or side impact that would cause breakage. Sharp tools, low heat build up and slower speeds when drilling or grinding are critical. Spalted woods will usually have some small voids and irregularities that can require fills with CA glue for a more uniform surface and finish.
Sure it is extra work, but the dramatic results are more than worth the extra effort.
This photo is to show a piece of maple burl with spalting that has been stabilized. Prior to stabilizing the areas to the right where the wood is blonde and reddish are the areas that would have still been hard wood. The grays and browns would have been cork like. After stabilizing the wood now has a more uniform hardness and durability making it usable.
Any questions or comments are welcomed.