Series editors' preface - Wood Tools

446 Conservation of Furniture
(a)
(b)
Figure 10.5 Types of clamping/cramping system. (a) Screw jacks cab be braced against a wall or ceiling.
(b) Folding wedges. Measurements across the diagonals of the frame should be taken to ensure it is square and
true. (c) (i) Cramping/clamping system for veneering a board: the clamps should be tightened in the order
indicated; (ii) cross-section of system illustrated in (i): the curve on the upper bearer has been exaggerated for
illustrative purposes. (d) Cramping a small area in the centre of a wide board
to ‘pinch’ surfaces together rather than using
brute force to compensate for poor workmanship.
The goal is to apply the minimum pressure
to the right area without damage to the
surface or distortion of the object.
Inappropriate cramping can cause both
minor and major damage to an object.
Structural distortion may occur if the weight of
the cramps pulls the objects out of true.
Cramps that are large or heavy in relation to
the object should be supported to prevent this.
Over-tightening cramps may cause plastic
compression of wood and, although reversible
in some instances, in others the damage is
permanent. Ferrous cramps may cause staining
4
(c)
2
1
Clamping order
3
(d)
5
bearer
caul
softening
veneer
ground
bearer
if left in contact with tannic woods that have
been dampened by the adhesive or removal of
any excess. It may be possible to ameliorate
this staining using an acidic solution (e.g. citric
acid) but the damage cannot be completely
reversed. A piece of scrap softwood or an
isolating layer of Perspex will prevent such
damage. An isolating layer of Melinex or silicone
impregnated release paper may be used
to prevent cramps or cauls from sticking to the
surface. Loss of decoration or transparent coating
may occur if excess adhesive is left on the
surface. Kolbach (1998) has described the use
of Peel Ply, a non-woven polyester release
fabric that has been treated so that adhesives
(i)
(ii)