Series editors' preface - Wood Tools

normally seen, so that it can be more easily
identified during examination.
Metamerism is a term used in colour
technology to describe the effect when two
colours that match each other under one light
source differ when viewed under a second
light source. The problem of metamerism and
pigments is discussed in section 12.3.2.
Metamerism may occur when colour matching
wood, not only as a result of changes in the
light source but the direction in which light is
reflected from the surface. A piece of wood
viewed from one direction may appear to be
a light colour but when viewed obliquely or
from the opposite direction the same area will
appear to be dark. This is particularly evident
when viewing timbers such as figured
mahogany or satinwood, which derive their
striped decorative effect from an alternating
grain direction. The light and dark areas of
such woods reverse according to the viewer’s
position and the direction of the light source.
The direction light will strike the object and
the position of the observer when the object
is returned to display must be replicated when
retouching wood with pigments and dyes.
Colour matching transparent surfaces on
wood may require the subtraction of colour
from replacement wood (bleaching). It may be
necessary to add colorants in order to match
the repair to the original surface. Addition
colorants may be opaque pigments or translucent
stains. When light strikes an object it will
be transmitted, reflected or absorbed thus each
layer of pigment or stain that is applied during
colour matching will have some effect on the
final result. Pigments and stains may be used
in a variety of binding media, and may be
applied separately or combined as desired.
The permanence or colourfastness of materials
varies widely and literature from the
manufacturer or supplier should be consulted.
A variety of materials and techniques are
discussed in general texts on the restoration of
antique furniture (Bennett, 1990; Rodd, 1976).
Whilst the traditional furniture restorer has
relied on materials that vary in their photochemical
stability, most notably shellac and
spirit-soluble stains, a range of more stable
materials are available for conservation colour
matching. In situations where furniture was
exposed to a significant amount of UV light
and was in use, periodic refinishing was
Conserving transparent coatings on wood 613
inevitable. As the colour of the surrounding
wood changes with exposure to light,
retouched repairs become progressively more
obtrusive. Whilst traditional finishers have
often tried to avoid the use of fugitive stains
in their work, in this context lightfastness was
less important than the ability of the surface
finish to withstand regular use. With the exclusion
of UV light from some domestic and most
museum environments, the need for photochemically
stable retouching materials and
binding media has become increasingly
important.
The process of matching a repair involves
surface preparation, staining, grain filling,
colour matching, coating and occasionally
distressing. Not all repairs require all these
steps but this provides a convenient way of
ordering the following discussion.
13.5.2 Surface preparation
The purpose of surface preparation is to
ensure that the surface of the wood repair is
free from blemishes and defects, and to
remove oil, wax, dirt and other contaminants
that might interfere with the application or
subsequent performance of the finish that is to
be applied. Materials used to abrade wood are
discussed in section 10.1.12. The decision
whether to match original tool or abrasion
marks may depend on ethical considerations,
Figure 13.3 Detail of a Victorian tea caddy, rosewood
veneer on pine. This is an example of poor
workmanship. A patch has been fitted to replace the
lost original veneer. In levelling the patch, original
finish has been removed from the adjacent surface. As a
result, the patch and adjacent area must be separately
colour matched