Series editors' preface - Wood Tools

of flakes and cups but care should be taken to
avoid causing bloom in varnish or otherwise
damaging moisture-sensitive surfaces. Finally,
an appropriate solvent may be introduced,
either as the consolidant carrier, added to an
aqueous consolidant or using a solvent-saturated
atmosphere, to achieve controlled solvent
vapour exposure. The swelling effect of such a
solvent should be minimized because a large
amount of swelling may cause further damage
as a result of plastic compression. If a large area
has become detached and is too brittle to be
laid in one go, it may be possible to work
across it in stages, though it is essential to avoid
the formation of ridges of consolidant underneath.
It is not unusual for the wooden substrate
under a decorative surface to shrink as a result
of sustained low RH. The shrinkage may be significant
enough that the cracked edges of decorative
surface overlap when relaid. There are
four options for treatment in such a case. The
first is to introduce and maintain environmental
conditions that will reverse or minimize such
shrinkage, but in reality this is rarely possible.
Alternatively the conservator can retain all original
material by laying the edges down so that
they overlap, remove original material by trimming
the edges to allow the area to be laid flat
and flush, or support the surface decoration in
its raised state (Webb, 1994). Removal of original
material is a decision that should not be
taken lightly. Furniture in general, and decorative
surfaces in particular, rarely survive the
vicissitudes of time unscathed and faults should
perhaps be accepted rather than hidden.
Facing
Facing a decorative surface has traditionally
involved securing loose or vulnerable material
to a surface by adhering paper over the area.
Facing is always intended to be a temporary
treatment. It is commonly used to prevent loss
of material if an object cannot be treated immediately,
to allow an object to be transported
without further loss, or to facilitate other conservation
treatments.
Facing paper should ideally be non-wet
strength, acid-free and with a random fibre.
Japanese tissue, rice paper, mulberry paper or
Eltoline tissues are suitable facing papers,
though in an emergency other materials such as
toilet tissue or cigarette papers may be used.
Principles of consolidation, aesthetic reintegration and coatings 573
The amount the facing paper shrinks as it dries
will depend on the type of adhesive and the
size of the facing paper used. Non-water-based
adhesives will cause least or no shrinkage.
When water-based adhesives are used, the
larger the area of the paper the more it will
shrink, so the maximum size that should be
used is around 10 cm. Any edges should be
feathered to avoid the formation of adhesive
ridges on the surface. This can be done quickly
and accurately by brushing a line of water onto
the paper, leaving it a moment and then pulling
it apart, or by folding the paper, licking the
edge and then tearing it. If more than one piece
of paper is used, the edges should be overlapped.
If the object is being prepared for transport
or structural work, several layers, each
slightly misaligned with the one before, may be
applied. Small strips may be used to bridge
splits or tears in materials such as leather.
Although water-based adhesives are the most
compatible with paper, allowing it to conform
to the vulnerable surface, moisture may damage
a varnished or decorated surface and nonaqueous
facing adhesives may be required.
Aqueous adhesives should not be used for
localized facing on canvas, for example,
because they may result in the formation of a
permanent ridge as a result of uneven exposure
to moisture. Blooming as a result of aqueous
consolidants may be avoided by applying an
isolating varnish, which should be selected so
as not to narrow later treatment options. The
adhesive mixture should be dilute to weaken it
and avoid shrinkage. Long-term stability is not
usually a criterion for the selection of a facing
adhesive, but may be a consideration if a large
number of objects are treated in an emergency.
If the surface to be faced is porous, the facing
adhesive should be compatible with original
materials and intended future treatment
(consolidation, infilling and retouching media).
If the nature of the surface that is to be faced is
unknown, it may be necessary to undertake
solvent tests to establish solubility parameters
in order to select an adhesive that will not damage
the surface. The adhesive selected will be
dependent on nature of surface to be faced.
Methyl cellulose, Beva 371, isinglass/gelatin,
PVAL, PVAC and acrylic emulsions and dispersions,
Paraloid B72 and B67 have all been successfully
used as facing adhesives. Wax/resin
mixtures may be problematic but can be useful