One of the joys of woodworking is being able to work with all sorts of different woods, and with woods that have different figures within them. I never get tired of looking at all the different designs and shapes that are comprised of different figured woods. It's almost like looking at clouds, they are all different, the beauty of wood, is they don't change like clouds do, they remain constant.
One of my favorite woods to work with is SPALTED wood. This kind of figure can occur in any wood and is basically caused by a fungus that invades the inner tree and in so doing leaves a path of lines and color changes that can bring out a very unique beauty to woods. It is far more noticeable in lighter color woods but can also occur in dark woods.
Spalting is the first breakdown of the wood fibers. It is where wood rot begins and if it is allowed to go too far, the spalting becomes rot and when rot goes far enough it can actually crumble and eventually would disintegrate and become part of the earth again ...
So knowing this, you need to be careful where you use Spalted Wood. It may not be suitable for the structure of what you build but may be better off as accent pieces, like door panels, door knobs, turned bowls and things like that. You have probably found spalted wood around your yard in the form of sticks, branches or old fence posts, but finding useable wood can be a bit more challenging, and you need the correct conditions ...
Specially, the wood needs to be in a place where it can remain damp for many months, or even years depending on how thick it is. When it is very thick, like a large tree trunk, there is a good chance at least part of the wood will have rotted and will be unusable, but other parts may still be ok, you never really know until you get it home, dried out slowly, and cut into boards or beams.
In our case we were able to find logs that had been on, or near the ground for what looked like a few years. What this did was allow the tree trunk to condition it'self by making the water content equal throughout the trunk.
A tree trunk, or even branches basically have 3 areas, the heartwood, which is often a different color, the sap wood which surrounds the heartwood and is what carries moisture and nutrients throughout the tree, and the cambium layer, a very thin layer just under back that is the growing part of the tree.
If you were to measure the moisture content of heartwoods, depending on the time of year and species, you might find it to be ... lets say 20%. By comparison the sapwood of the same tree might have a moisture content of say 40%. What we want to do in order to try and prevent the log from cracking is to stabilize the moisture inside the log so that the the moisture content of the heartwood and the sapwood are the same or at least much closer.
To prevent the rapid release of moisture we seal off the ends of the log because this is where most of the moisture can escape, and very quickly, which is one of the reasons why logs crack, they are not end-sealed. By sealing the ends, we trap much of the moisture in the log which does 2 things, it forces the water inside equalize the heartwood and the sapwood, and it also forces the log to expel water through the sides of the log rather than the ends. This process also helps to keep the moisture moderated inside the tree so it will gradually dry out, an in most cases will not crack, because it is drying slowly through the sides.
Sealing the ends of freshly cut logs is important because we want to stop the immediate release of moisture out the end grain. As a side note, even all of the pre-cut lumber that I store outside, I end-seal it as well to help reduce the ends from splitting.
The product I use for end sealing is called Anchoseal (from U C Coatings) unfortunately it is not easily found at your local home-reno type box stores but you can purchase it online direct from the company.
There are alternatives for sealing end grain, for example water based paints such as latex are better than nothing. For them to really work you need to apply several coats, applying each coat after the previous has dried.
Another method I have tried with limited success is to simply apply wax to the end grain by rubbing the wood with a brick or paraffin wax, it works ok on smaller pieces but larger ones it is tedious.
Whatever method you come up with will be better than doing nothing and over time will help reduce the incidence of splitting a warping.
When To Cut
I am as anxious as everyone else to cut into a log to see what is in there, but for this, patience is vital. After the log is consistently around 12 - 14% (or lower if possible) throughout, that means the center or heartwood as well as the out areas or sapwood are all measured at the same moisture lever, will be the time to cut into it and make some lumber. At this point, if the log has not split the board, when dry should be very stable with little or no warping ... if all goes well. Of course there are no guarantees, but your chance of reducing or eliminating checking and warping are much reduced by endsealing and waiting for the wood to dry slowly than not sealing and watching the log check and crack to the point that with some they become useless for woodworking.
Copyright - Colin Knecht