Series editors' preface - Wood Tools

example, extensive treatment on one object
may mean many other objects are left untreated.
Preventive conservation measures,
including environmental control, disaster
preparedness and high standards of housekeeping,
will result in more long-term benefit
to objects than the most skilled intervention.
10.1 General principles
When attaching new material to a wooden
object there is usually a general procedure that
is followed regardless of the specifics of the
damage. First, the cause of failure should be
diagnosed as this will inform the conservator’s
choice of treatment. If wood is to be used as a
repair material, a suitable piece is selected and
then shaped. It may be necessary to create a
suitable surface on the object to receive a
repair to ensure the repair will fit snugly or
provide a clean surface for gluing. Two options
are building up the surface with a carvable
epoxy (isolated from the original with
animal/hide glue) to allow a flat surface to be
chiselled, or planing a broken surface flat.
Thus preparation of the object and the repair
piece often go hand in hand. A suitable adhesive
and/or joint is selected and the repair
secured in place after a dry run of the procedure
is carried out. When the adhesive has
cured the repair is shaped to its final dimensions.
Finishing and colour matching of
varnished wood is discussed in Chapter 13.
10.1.1 Diagnosing the cause of failure
Understanding the cause of structural failure is
an essential prerequisite to a conservation
treatment. It is important to understand why a
structural failure has occurred in order to tailor
a treatment that will address the problem rather
than causing more extensive damage in the
future. Analysing the cause of failure may
make it very clear that in some cases no
permanent or completely satisfactory treatment
is possible due to original construction techniques
or materials, or the environmental
conditions in which the object is kept (e.g.
fluctuating RH).
Common causes of structural failure in wood
include insect infestation, misuse, the physical
and mechanical properties of the wood itself,
Principles of conserving and repairing wooden furniture 437
such as weakness in areas of ‘short grain’ or
warping due to internal stress. Factors related
to environmental conditions include loose
joints or splits that result from compression set.
It is unavoidable that wherever the movement
of a component is restrained by a fixing or
joint, fluctuations in relative humidity will
result in differential shrinkage, compression set
and splits (Hoadley, 1978, 1980). Other problems,
such as warping, may be caused by postconstruction
treatments such as the application
of veneer or a surface coating to one side only
of a component. The deterioration of wood
and wooden structures is discussed in detail in
Chapter 7.
Where the object is kept in an environment
with fluctuating RH, the conservator must
allow for some inevitable movement of the
wood, either by the selection of materials or
repair technique. If such allowances are not
made, the problem will reoccur and the area of
damage will be extended. If the cause of the
damage is inherent in the original construction
of the object, for example splits arising as a
result of cleated boards, a weak repair will
break before failure occurs in an adjacent weak
area and will thus prevent extension of the
area of damage if the problem recurs in the
future. It may be possible for the conservator
to make use of techniques specifically developed
to compensate for uneven movement,
such as buttons or shrinkage plates (see Figure
10.16), to reattach a table top to an underframe
after treatment. It may also prove necessary
to resist demands for the impossible by
those who do not understand the inherent
properties and limitations of wood.
10.1.2 Selection of repair method and
repair material
Once the nature and cause of failure is understood
a repair method and suitable materials
must be chosen. These two factors are interrelated
and the conservator must often balance
contradictory treatment priorities. Intended use
after treatment will also define the repair
method and material – for example a chair
with a broken leg may require a different treatment
if it is intended for museum display as
opposed to regular domestic use. The aim is to
select a repair material with appropriate properties
and apply it in such a way as to achieve