The Technique of FURNITURE MAKING

Plywood grades

Grading rules differ according to the country of origin, and the following list is therefore a general indication only.

A Face and back veneers practically free from all defects.

A/B Face veneers practically free from all defects. Reverse veneers with only a few small knots or discolorations.

A/BB Face as A but reverse side permitting jointed veneers, large knots, plugs, etc.

B Both sides as reverse of A/B.

B/BB Face as reverse of A/B. Reverse side as

reverse of A/BB.

BB Both sides as reverse of B/BB.

WG Guaranteed well glued only. All broken

knots plugged.

X Knots, knot-holes, cracks and all other defects permitted.

Marine Quality High-quality product usually of fir, makore, mahogany or similar highly durable wood throughout, bonded with phenolic resin glue to WBP specification. (Must withstand 72 hours boiling in water without failure of the glue-lines.)

Additionally the United Africa Company grade their Cresta plywoods under Gold, Silver and Blue labels. Construction is the same throughout, and the grading refers to the face appearance only. The bonding is phenolic resin to WBP specification, and every sheet is impregnated against insect attack (lyctus, furniture beetle, termites, etc.), which does not affect the gluing or polishing properties.

In practice it is not wise to go below BIBB, BB or grade 2 for veneering, while Douglas fir ply is altogether unsuitable owing to the upraised grain, and therefore grading rules for this particular kind of ply have not been included. It can be assumed that, unless specifically stated, all plywoods are dry glued, i. e. the veneers dried before gluing, and that except for the very lowest grades not suitable for furniture both the face and reverse are sanded flat for immediate use.