DRYING WOOD

MOISTURE CONTENT

For most woods the best tradeoff point between efficiency and safety is about 10%, with 8% as a good rule of thumb, 12% should be your maximum. At 6% or below most wood becomes too brash and brittle. Above 12% and most wood becomes too limp and sluggish and is much more prone to taking a severe set. Tension-weak woods are safer with moisture contents a point or two higher than normal. Tension strong woods favor a point or two lower than normal, for example, at 6%, hickory's cast improves drastically while remaining normal tension safety.

DANGERS

The main dangers of drying wood are checking, warping, cracking, and internal crushing of wood cells. This happens when wood is dried too quickly for its girth. The thicker the wood the slower it must dry. Wood checks when its exterior dries and shrinks quicker than its interior. Uneven surface drying, and non-symmetrical cross sections cause wood to warp. Once wood is reduced to near bow thickness, there is no interior, so to speak, so the stave is immune to all forms of drying damage. By reducing it to bow thickness it will now dry in days instead of months or maybe years. The quickest way to dry wood is also the safest. This is one the of the most essential tips in bow-making that I have ever learned and it can save you time, heartache, and broken or poorly crafted products.

QUICK DRYING

Fell and split a tree into staves, take one stave and pull the bark off. Now rough out your bow leaving width and depth, then floor tiller it just as if you're making a finished bow. The more uniform it is in thickness the less it will want to warp. Now lay it out on a 2x4 with spacers under it. Clamp it on the spacers so that warping can be kept to a minimum, yet air will be allowed to flow around it freely. Now place it where the relative humidity is 40% or less. The warmer the air the faster it will dry and a gentle flow of air will shorten the dry time considerably.

NOTES OF INTEREST

 Relative Humidity determines moisture content.

       relative humidity                        equalized moisture content

30%                        =                          5%

43%                        =                          8%

      55%                        =                        10%       

65%                        =                        12%

75%                        =                        14%

Dry a stave to a moisture content matching the humidity in which it is to be stored.

At a given relative humidity all woods dry to the same moisture content.

FORCED DRYING

In a stave dryer, a green stave freshly cut can be reduced to the desired moisture content to make a good bow in about 5 days. At 100 degrees Fahrenheit and 40% relative humidity, a floor tillered stave can reach 10% moisture content in about 5 days. It will reach 8% in a couple more days if this is the moisture content desired. A higher temp will speed up the drying time and the relative humidity determines the final moisture content. Caution!! Approach temps over 100 degrees very carefully, the results vary with different types of wood and you can do damage to some woods.

A DRYING BOX

Drying boxes are convenient if you need a dry stave during your high humidity season. Or if your "dry season's" relative humidity is high enough so that it takes a long time to cause the moisture content to creep down to tolerable levels. More on dry boxes later when I will give you several different plans for building and some charts to go by for dry times for specific woods.