Preparation Of Groundworks Or Substrates

Either solid or prefabricated woods (plywoods, particle board, etc.) can be used for veneering provided they are stable, mild mannered, not too coarse in the grain and free from defects, although heated animal glues (hide glues) should not be used for particle boards as they tend to swell up the surface chips. Very absorbent woods should be sized before laying, defects cut out and filled with plugs cut to follow the grain (280:1); holes and depressions filled with plastic wood, wood-dust and glue, or plaster of Paris and glue (not wax-based stoppers or putty). The usual advice given that the groundwork should be well scoured with a toothing-plane to roughen up the surface as a key for the glue is not strictly accurate. The old toothing-plane is undoubtedly an excellent tool for the general hand-levelling of bumpy surfaces, but glue sticks by molecular attraction, although some degree of mechanical attachment is usually present, therefore keyed surfaces are not really necessary (and might even interfere with the bond). Provided the surface is reasonably absorbent and not glazed with age or dirt, or with a very hard burnished grain, a light scouring with abrasive paper followed up with a thorough dusting is all that is necessary, and this applies to veneers also.

These should be laid 'with the grain' on solid boards which are liable to shrink across the width, but 'across the grain' of prefabricated boards if these are already faced with knife-cut veneers, as the innumerable stress cracks caused in the cutting will only augment those in the facing veneers if they are both laid together with grains parallel (see Veneers, Chapter 2). End grain should be repeatedly sized with weak glue to lessen the absorption, but even this is a risky procedure and end-grain veneering should be avoided wherever possible. Veneering over surface joints, lap dovetails, tenon shoulders, etc. should also be avoided, for they will eventually show through as definite sinkages or stressmarks in the face veneers (287:1, 2).

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