.Tainuiij- 10. mn 



Heartwood and Sapwood 



Hu Maxweli,. 



Editor's Note 



Woods of various kiutls are more cai'otuliy assorted and inspected llian they used to be. in 

 order to select those best suited for particular purposes. Chauce and accident do not enjoy the 

 privilege once accorded them iii deteruiiuing what kinds and grades of lumber shall supply a" given 

 lustry. Properties and qualities hold first place now. IIaedwood Kecoro plans a series of articles, this 

 being the first, in whicli will be discussed, in a plain w ay and as free as possible from technical diction, pu( 

 properties and qualities of wood as strength, hardness, e iasticit.v, color, taste, odor, figure, seasoning, and others, 

 with the particular piiriiose in view of discussing how thes t qualities can f)e used tn liesi advantage by manufacturer 



AilTICLE 1 



The outer portion of a tree's trunk, immediately beneath the bark, 

 is commonly known as sapwood, or "sap"; and the inner part is 

 heartwood, or ' ' heart. ' ' The two portions are usually distinguishable 

 by their contrast in color, the sapwood being lighter, heartwood 

 darker; but that distinction does not always hold. Some trees show- 

 little difference in color between heart and sap, as basswood, willow, 

 black gum, holly, spruce, 

 fir, hemlock, and cucum- 

 ber. In some instances 

 the deeper color belongs 

 to the sapwood, such as 

 yellow locust, Texas cat's 

 claw, and same other 

 trees that bear pods and 

 belong to the pea family. 



There is no statidard 

 by which to state the 

 average thickness of sap- 

 wood. That depends on 

 the species, the age of 

 the trees, and the rate of 

 growth, as well as on 

 what seems to be acci- 

 dental. 



Sapwood is alive ; 

 heartwood it without life. 

 The former is active in 

 promoting the tree's 

 growth ; the latter acts 



only as a support of the trunk's weight. Water, which is taken up 

 from the soil by the tree's roots, rises by means of pores or other open- 

 ings up through the sapwood until it reaches the leaves, and there it 

 is converted into a fluid that is capable of building new wood. It 

 then descends along the inner bark, chiefly, and is the ]>rincipal agent 

 in a process that forms a layer of new wood just under the bark, in 

 all parts of the tree, trunk, limbs, branches, and twigs. Heartwood 



has little or nothing to do with this process. It may be of some use 

 as a storage place for superfluous tree food, or building material; but, 

 to all intents and purposes, heartwood is inert and dead. It matters 

 little if the heart decays and leaves the trunk hollow, as often hap- 

 pens with large sycamores. That does not interfere with growth of 

 the trunk, because the outside shell contains all the wood that is con- 

 cerned witli the growth and health of the tree. 



Change from Sapwood 

 TO Heart 



Every particle of wood 

 in every hardwood or soft- 

 wood tree is sapwood be- 

 fore it becomes heart. The 

 process of cliange from 

 the former into the latter 

 is simply the progress of 

 death. Young trees are 

 alive through and through 

 and are all sapwood until 

 they attain some size and 

 reach certain ages. Then 

 the wood near the center 

 of the stem dies. It 

 ceases to be instrumental 

 in carrying water from 

 the roots to the leaves, 

 and the cells, which are 

 minute tubes or vessels, 

 harden and thicken. They 

 then become more or less clogged with gum, resin, tannin, and other 

 substances which impart the dark color that usually characterize heart- 

 wood, and generally ificreases its weight at the same time. 



Every year or every few years portions of the inner layers of 

 sapwood die and change to heart. In a general way, this change con- 

 forms to the rings of annual growth ; but that is not a fixed rule. The 

 dividing line between sap and heart frequently does not follow a 



WHILE IN SOMK CVSES CED.\R CHEST llAXUI-WCTiatEllS ELIMINATE SAP 

 AS FAR AS POSSIBLE. OTHERS CONSIDER THAT A THIN STREAK HERE AND 

 THERE ADDS TO RATHER THAN DETRACTS FROM THE APPEARANCE 



CONCENTRIC HEARTWOOD AND SAI'WOOD 

 This is common with yellow poplar and white 

 pine and generally yields a high perceutago of 

 clear lumber. 



SAPWOOD AND HEARTWOOD LOPSIDED 

 Met with oftenei- in hardwoods than in soft- 

 woods. Tendency is to become symmetrical as 

 trees grow old. 



FANTASTICALLY FORMED HEARTWOOD 



Rocky Jlountain juniper. Somewhat com- 

 mon with other junipers. E.\cellent material 

 for shirtwaist boxes. 



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