Teak Sapwood vs. Teak Heartwood

We have conducted some non-scientific tests on teak sapwood and we offer here our beliefs about teak sapwood.

What is sapwood? Sapwood is the outer living part of the tree. As the sapwood grows new layers around the tree, the old sapwood dies and becomes heartwood. So all heartwood was sapwood at one time. There are not two species of wood here, it is all teak. Many trees have different color sapwood and woodworkers use it all. For example: red cedar, cherry, mahogany, and walnut to name a few.

Weight - A teak heartwood board 1 x 4.25 x 98 inches was found to weigh 12 pounds and 6 ounces.

A teak sapwood board the same size was found to weigh 12 pounds and 4 ounces.

Conclusion: the sapwood is lighter but only by a very small amount when testing boards of equal size and age.

Hardness - We smashed a 1 pound finishing hammer into both the teak heartwood and the teak sapwood and found no dent with an equal flat strike. Again, with an angled strike, the hammer head created a small dent of equal size in both test boards. Conclusion: the sapwood is as hard as the heartwood (after kiln drying).

Rot and Insect resistance - Insects lay their eggs in the bark of trees and when hatched, the larvae eat the sweeter living part of the tree until they mature and morph in adult insects. Here is where we distiguish between Kiln Dried and Air Dried wood. When the bark is removed and the wood is immediatly kiln dried, any beetle larvae are either removed before development, or get cooked in the kiln process. A wood kiln is really just a big oven used to dry out the wood. The process of heating up the wood and cooling it draws the moisture out of the cell structure of the wood. Kiln drying takes 2 or 3 weeks depending on the thickness of the wood. Wood eating insect larvae will not invade kiln dried wood just as they do not invade the heartwood, because it has dried out and lost it's moisture and sap content. As the sapwood is dried it's cell structure shrinks and becomes harder as it does when it becomes heartwood. Conclusion: kiln dried sapwood is very similar to the heartwood. In fact, it is grown together as the same tree.

On the contrary, when wood is air dried. The drying process is very slow, about an inch a year. So it takes 1 year for 1 inch thick, 2 years for 2 inch thick, etc. Temperature and climates will affect this drying too. If teak is air dried, the sapwood can become infested with insect larvae and the extended time of high mositure content can allow the sapwood to become infected with bacteria and mildew spores which can cause rotting. In a dry season this air drying is not so bad as during a rainy season or tropical climate. In a wet tropical climate,it may be difficult or impossible to properly air dry teak. Conclusion: green or air dried teak has sapwood that is softer, contains more moisture, and is subject to insect infestation and bacterial rotting.

Oil and Mineral content - As the tree grows minerals and water are brought up from the roots as sap and in through the leaves transdermally.. The sapwood is the growing area of the tree and therefore what is in the heartwood came from the sapwood since all the heartwood was sapwood at one time. So what is in part of the tree is in all of the tree. The durability of teak is due to its ability to repell water which is because of its density and "oil" content. I believe that the kiln drying process "pulls" these naturally occuring "oils" along with the moisture content (sap) out through the sapwood as the wood dries out. Conclusion: the sapwood has the same ( or nearly the same ) properties as the heartwood after the kiln drying is done. 

Teak oil does not come from pressing teak trees. Teak oil which is sold in marine stores is usually a combination of linseed, mineral, and tung oils with mineral spirits as a thinner. This teak oil can be used on many types of wood to enhance the wood's ability to repell water and to keep it from cracking and splitting in the hot Sun.