ENDING THE BENDING A general overview on the straightening of warped wood Why wood warps First of all, what is wood? It is a sponge like material made of cells and fibers that swell and shrink depending on the temperature and moisture in the surrounding air. When a tree is cut down, first of all the water in between the cells evaporates, then shrinkage sets in as some of the water inside the cells dries out. Drying from it's green condition, wood will retain it's original dimensions until the moisture content falls to about 30% from which point it will shrink as it dries. The moisture content is expressed as a percentage of the dry weight of the wood: a piece which is half dry wood fiber and half moisture will therefore have a moisture content of "100%". A certain percentage of bound water (that is the water within the cells) always remains. With thorough air-seasoning, the moisture content of most types of wood will fall between 17% and 23%, at which level it will be in balance with the moisture content of the air around it. When the moisture content falls below 17% the wood will tend to twist as it dries out. A cool environment with a relative humidity of about 55% and a little bit of air movement is said to be ideal for wood objects in general. You want to be informed about this. Gradually turn up your thermostats as autumn approaches and lower the setting step by step when spring comes. A sudden change in the circumstances is the worst thing possible as the moisture will be sucked out of or pushed into the material far to quickly causing even more tension inside it. Treatment Now that we have an idea why and how wood warps, it's time to do something about it. Non-intrusive treatment Non-intrusive treatment would be changing the environmental circumstances, with little risk of damaging the object further. When a piece of warped or twisted wood is placed in a damp environment, it might just return to its original shape. Minimal interventive treatment When changing the environment is not enough, you can either try to straighten the piece of wood or adjust its context accordingly. Humidity and heat partially soften the lignin and hemicelluloses in the wood, allowing the wood fibers to slide along each other. After cooling and drying, they return to their initial state and the wood maintains its new shape. Introducing moisture can be done by placing the wood in a warm and humid environment. When the wood to be treated is thick (as in the case of a skateboard deck) steam may be required. You can use something as simple as the bathroom at home (steam from the shower works great). The moisture content needs to reach about 25%. During this process the skateboard is placed in the "Twister", counter-twisted and locked into place. Leave it in place for one week, then release the clamp and check the straightness of the deck. If the twist reappears, clamp it back in place and leave it for another week. After the desired straightness is achieved, the deck then needs to be dried. Clamp it back in the "Twister" and place it under a warm light, a standard household lamp will work. Leave it for about 24 hours, checking it periodically. Remove the deck from the "Twister" and your done. Generally speaking wood will want to return to its disfigured state sooner or later. This phenomenon is called spring-back. The chances of experiencing a spring-back reaction are greatly reduced when the wood is counter-twisted and left for a period of time, say a week or two. Because not only the cells on the concave side are compressed, but those on the other side as well, the tension in the wood is spread more evenly and chances of spring-back are minimized. If you have any questions, comments, or concerns, contact Brandon at: The Original Twister 9200 W. Douglas Wichita, KS. 67212 theoriginaltwister@hotmail.com 316-214-7743