Steve Maskery":3k9da5fp said:
My understanding is that beech is seamed for two reasons.
1. The colour can vary considerably so steaming allows the dyes to run and blend the board
2. Beech is hard, yes, but also quite unstable. It's not unusual for a board to open up wildly as it is ripped, resulting in a pair of bananas. Steaming stabilises the timber, although I have no idea why or how it does so.
Neither of your statements are quite correct Steve. Here's a slightly more detailed discussion of steaming wood extracted from a manuscript I'm working on, how its done and why it's done. Slainte.
In Europe pink coloured steamed Beech is available, and Black Walnut supplied by large commercial North American drying operations is another species that is sold after it’s been steamed. In the case of walnut the purpose of the steaming is to make the sapwood the same colour as the heartwood. Many woodworkers believe the steaming spreads the pigments from the heartwood into the sapwood, but the following quote argues against this. “The process does not involve diffusing pigment from heartwood to sapwood.” (Tindall, 2007, p 32.) He goes on to describe the process using purpose built steamers after the kilning operation. The boards are close stacked* and loaded into the steamer, the doors closed, and the inside of the steamer flooded with hot wet steam. As long as the wood rises to the temperature of boiling water, the atmosphere is very wet, and these conditions held for a couple of days the sapwood will turn dark and closely match the heartwood. According to Tindall, when the wood leaves the kiln it looks as if it’s covered in soot, but this planes off to reveal a uniform purple colour throughout.
*Close stacked aka ‘dead packed’ timber describes packs of dried boards or planks stacked tightly together with few or no spaces. A couple of advantages of close stacking are: boards maintain their dried MC better through prevention of air circulation, and take up less space during storage and transport.
Many furniture makers object to this steaming process because of the uniform colour. They prefer the richer and more varied colours of air dried walnut. Whilst I agree that air dried walnut has these attractive characteristics initially, it’s my experience that within a few months, and at most within a year or two of a piece of walnut furniture going into service, it’s usually almost impossible to tell the difference between air dried and steamed walnut. By that time nearly all walnuts seem to mature into the soft honey browns we’re used to seeing in furniture that’s seen some service, or indeed, many years or decades of service.
The driving force behind the common practice of steaming American black walnut is the main market for the material and the American grading system. Sapwood is not a fault in American grading, and the clearest, least knotty planks come from the outside of the tree during the milling into boards. Naturally, these boards from the outside of the tree contain the most sapwood. The biggest buyers of the wood are big furniture manufacturing businesses, either in North America or, increasingly, overseas with China being one example. Unlike the small furniture business, or amateur woodworker, the big furniture makers generally cut up larger planks to remove defects, rearrange them and glue them back together to make up required widths, and even lengths. So to these businesses, long, wide and clear boards of walnut aren’t their primary concern. If the small furniture maker requires long, wide and clear walnut planks with all the interesting colours to start with, their only recourse really is to seek out specialist suppliers: this almost certainly means paying a premium over the commercially kilned material.
Steaming Beech evens out the colour of the boards much as steaming walnut does and the process makes the wood easier to work than unsteamed White Beech. Recently I’ve come across steamed north American Birch for sale in timber merchants and the process gives the wood an even rich chocolate colour.
