Q. We are just now getting into maple cabinets and have a problem. We can color match the pieces but when we put them into a door, sometimes one piece will look like it is not even close in color to the other pieces. Yet we know that they did all look alike. This is before finishing; the same is true after finishing. Second question: We sometimes see maple that seems weak and does not hold screws in the hinges well.
A. The angle that you view maple from, especially soft maple, will result in different color. That is, if you rotate a piece 180 degrees end-for-end (or even 90 degrees) and view from the “other side,” it will appear different. This is a characteristic of maple. A finishing specialist would have to tell you how to cancel this natural effect using fillers, stains, etc.
Regarding maple properties, I suspect that you are seeing a species difference and perhaps some normal variation within the species. There are five different species of maple and each has different properties. The five are sugar maple, black maple, bigleaf maple, red maple and silver maple. Sugar and black are sold together as hard maple. Bigleaf is usually sold alone as it grows mainly in Washington and Oregon. Red and silver are sold together as soft maple.
Most strength properties are related to density of the wood. So, here are the 8 percent MC density values: sugar, 40 pounds per cubic foot; black, 36 pcf; bigleaf, 31 pcf; red, 34 pcf; and silver, 30 pcf. Ultimate strength (MOR) values are sugar, 15,800 psi; black, 13,300 psi; bigleaf, 10,700 psi; red, 13,400 psi; and silver 8,900 psi. Hardness values are sugar, 1,450 pounds; black, 1,180 pounds; bigleaf, 850 pounds; red, 950 pounds; and silver 700 pounds.
Although I do not know of anyone asking for only sugar maple without any black maple, soft maple buyers will often ask for silver maple only with no red maple.
Cracking in maple chairs
Q. We have received several hundred unfinished maple chairs and cabinets from a company located outside the United States. We noticed that the items are checking, splitting and cracking after the finish is applied. I checked the moisture content this morning and the range is 9-12 percent MC. Can we put these in our dry kiln with just the fans on and dry these chairs? How long would that take? Should we add steam? We feel that 8-9 percent MC would eliminate the splitting.
A. First, we know that if you see cracks, or if the wood changes size or shape, it is due to moisture changes. So, you are indeed correct that the pieces were made at an excessively high moisture content for the environment where the items are now being kept.
If, after the wood has cracked, which means that the wood has lost some moisture already, and you find 9 to 12 percent MC, we know that prior to cracking the wood was even wetter. If the cracks are quite large, then the wood was substantially wetter than 9 to 12 percent MC. We know that wood products in most interior locations in North America average about 7 percent MC, which is about 38 percent RH. In the summer, we may see 8 to 9 percent MC and in the winter, 5 to 6 percent MC. Your suggested target of 8 to 9 percent MC might be a bit high...there will be some additional shrinkage (cracks will grow, maybe some warp, etc.) that will occur during the heating season.
I do not see how drying the pieces in a dry kiln will result in any difference in shrinkage compared to drying the pieces in an interior environment. (One exception would be a drying oven where the conditions would be extremely dry; usually the resident time in such a dryer is so short that the wood does not have a chance to react.)
I am not sure what you plan to do with the items, but one possible solution to consider, albeit quite expensive, is to dry the pieces to 7.0 percent MC and then repair the cracks using glue and a wooden spline to fill the gap. You may have to machine a groove in order to fit in a spline. Because of the annual movement of wood, it is not likely that putty will provide a quality solution.
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