March 10, 1917 



Hardwood Record — Veneer & Panel Section 



25 



Veneering with Two Woods 



Some Causes of and Remedies for Warping of Flat Stock 



HERE SEEMS TO BE MORE OR LESS 

 TROUBLE in certain classes of veneering work 

 where it is desired to have woods differing 

 materially in their texture on opposite sides of 

 a panel or a bit of built-up work. There is probably 

 more call for this in door-making than in anything else, 

 and complaint has been made that a door made of oak 

 on one side and cypress on the other will get crooked. 

 Yellow pine and oak, it is said, will work better. Thus 

 we find there are probably different woods which have 

 the same co-efficient of contraction in the process of 

 drying out thoroughly, and that there is enough difference 

 between some species of wood to make it a rather ticklish 

 job to undertake making a piece of built-up work with 

 one kind of wood on one side and another kind on the 

 other. 



What is probably the simplest solution of the whole 

 thing, when it is desired to have a different face wood 

 on each side of a door or panel of any kind, is to make 

 the face veneer very thin; thin enough that it will not 

 have any material effect in shaping the body, then build 

 the body up, independent of the face, of another kind 

 of wood. This will give stability and relieve the tend- 

 ency to strains set up by using two or more kinds of 

 wood, and the face veneer, being thin, will not have a 

 material effect on it unless it is an usually light panel. 

 By thin face veneer is meant veneer that is not thicker 

 than 1 ^20-inch, possibly thinner in some fine woods. 



It requires a little more care to use and finish off this 

 extremely thin veneer. If the center piece is built up of 

 veneer instead of a solid core, it calls for a little more 

 gluing because it must be three or five-ply and the veneer 

 face come on afterward. Yet this is the way to get 

 success out of veneering where there are one or two 

 kinds of wood on the face, and vs^here opposite faces 

 are to be of different woods it is the simplest way to safe- 

 guard against the trouble incident to unequal contrac- 

 tion of the wood in the process of final seasoning. 



In the making of doors, where this trouble is com- 

 plained of most, there has been a practice in the past of 

 using veneer sometimes '/^-inch thick on both sides 

 of the door stile. Where stock as thick as this is used, 

 with different woods on opposite sides of the door, 

 there is naturally a chance for the door to crook one way 

 or the other, unless a great deal of care is exercised in 

 drying the material and doing the work. It is better, 

 of course, to make a heavy core body and use a lighter 

 veneer, but where it is desired to use thick veneer, one 

 should study the nature of the two woods to be used. 

 If on one side there is a wood which will shrink per- 

 ceptibly endwise in drying, while on the other side there 



is one of very little shrinking, one way to safeguard it 

 is to put the stock in cauls and press forms that are 

 slightly curved toward the side of least final shrinkage, 

 then if the line of curvature is figured out carefully it 

 will be enough to allow for the final shrinkage in flat- 

 tening up. This requires some very delicate experi- 

 ments and careful measuring that many a door manufac- 

 turer is not in a position to carry out. Some men guess 

 at it and do very well, but guesswork is too uncertain in 

 working door frames. 



The veneer as well as the core wood should be thor- 

 oughly seasoned before using, and then dried out. This 

 involves not only drying primarily, but seasoning in the 

 air and then redrying for the final using, until all mois- 

 ture is out and all shrinking has been done. With even 

 the most thorough work in this it will be found that 

 when you spread your veneer and core with glue it will 

 absorb a certain amount of moisture from the glue. 

 Now, it doesn't take long for the glue to set and the 

 stock to be apparently all right and thoroughly dry. Still, 

 you must bear in mind that the moisture with which the 

 glue was mixed has simply been absorbed into the body 

 of the wood and must be given time to dry out and for 

 the wood to attain its normal condition before it is 

 through with swelling and shrinking tendencies. In short, 

 after work of this kind is taken out of the forms it 

 should be carefully piled on a firm foundation, straight, 

 weights put on it, and left in these piles to dry for several 

 days — that is, to dry and temper. Then when it finally 

 assumes its normal condition in the straight form it will 

 be found that most of the tendency to crook and warp 

 has disappeared. 



In making thin panels it quite frequently happens that 

 stock taken from the forms after, say, twenty-four hours, 

 and then trimmed to size and piled in the warehouse, 

 will crook or warp more or less. Maybe not all of it; 

 just a few pieces here and there, and some of them look 

 like they are ruined. Examination of them shows that 

 at times there is one kind of wood on the front and an- 

 other kind on the back. It may be some furniture panels, 

 with an oak face and the body and back cottonwood or 

 gum, or it may be a gum panel with gum faces, back 

 and center, or an oak panel, with oak on both the face 

 and back, and gum in the center. In fact, it has been 

 found that some of them will crook more or less no 

 matter what the combination of veneer front and back, 

 and it is evidence of some swelling and shrinking end- 

 wise not enough, probably, to be noticed in ordinary 



measuring, but it makes itself felt in a panel of any size, 

 and seems unquestionably to be caused by the taking up 

 of moisture from the glue, and the influence of this mois- 



