DRYING WOOD FOR TURNING #2: What we learned

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Blog entry by Wildwood posted 09-29-2016 08:11 PM 915 reads 0 times favorited 0 comments Add to Favorites Watch
« Part 1: WHAT YOU NEED TO KNOW Part 2 of DRYING WOOD FOR TURNING series no next part

After checking out the Wood Handbook hope everyone has a better basic understanding about trees and wood drying process. Whether wood is air or kiln dry to a certain moisture content doesn’t mean it will stay that way.
Looking at a tree stump learned a tree starts with outer/inner bark, layer of cambium, sap wood heart wood and at the center of all that is the pith. Sap is mostly water. In compression/reaction and abnormal wood the pith will not alway be in the center of the log.

Anyone that has mounted a piece of tree onto the lathe sometimes cannot tell difference between outer/inner bark, or see the cambium layer while turning. On some trees those things very pronounce. Who hasn’t seen a picture of turned item with bark, cambium layer, and bare wood why dothose turners thinks its all bark?
You all understand hoe wood shrinks as it dries, normally starts with free water in cells evaporating, but bound water still clings to cell walls. Depending upon reference once wood reaches fiber saturation point (FSP) of 25 to 30% MC wood starts shrinking.

Hopefully you now know drying wood is simply water removal process through evaporation. We have to end seal our logs as we process them becuase moisture escapes 12 to 15 times faster from the ends verus sides. Wood dries from the outside in. If we don’t slow down the drying process you will get greater tangential than radial shrinkage and see cracking at ends or along log section. End grain suface checking normally appears sooner. Easier to understand wood dries from the outside in, sap wood dries faster than heartwood and if we don’t slow down drying process get both cracking/splitting and end checking.

Wood will dry faster in warmer to moderate climates than freezing climates. Early on in the drying process air circulation enough applying too much heat not good. Harvested bunch of Mulberry, split, end sealed and put on a pallet threw a tarp over it during month of August. With little air circulation and direct sunlight for most of the day cooked the wood.

-- Bill

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