Series editors' preface - Wood Tools

756 Conservation of Furniture
If the japanned layers are in good condition,
the first step in a cleaning treatment is to
remove loose dirt with a soft brush. If the
japanning is poorly adhered, lifting, flaking, or
if the surface is broken up, the brushing must
be undertaken with care. In some cases it may
be possible to dust individual flakes, whilst in
others consolidation may be required before,
or at the same time as, cleaning.
Should the layer of dirt be more firmly
attached than can be removed with a brush,
dry cleaning methods, discussed in section
11.2.4, may be appropriate. If neither of these
methods is effective, one must move to the
next step in cleaning, which is the use of
liquids. Liquids must be used with caution and
solubility tests should be carried out prior to
use. One must not only consider the solubility
of the surface but the possible solubility of the
underlying layers as well. The liquid must not
be allowed to penetrate through the surface to
dissolve an underlying layer. Underlying layers
may be soluble in alcohol, aliphatic or aromatic
hydrocarbon solvents or water. If one of the
underlying layers is more soluble than the surface,
cleaning should be discontinued. Liquids
can be applied on a cotton swab, which is then
rolled over the surface to remove dirt. If the
surface is sound, some pressure may be
applied. Avoid scrubbing the surface as even
the finest cotton may abrade a highly polished
surface. Many fabulous surfaces have been
ruined from over-zealous cleaning. The
cleaned areas should be dried with a wad of
the same soft cotton. Only the finest, purest
cotton should be used for cleaning japanned
surfaces.
Since a great many japanned surfaces remain
soluble in alcohol, it is not recommended for
cleaning. Most japanned surfaces are not soluble
in aliphatic hydrocarbons so these would
be the first solvents to try. In the eighteenth
and nineteenth century a large portion of
asphaltum may have been included in the original
formulation of oil-based japanning.
Because asphaltum remains partially soluble in
petroleum based products, it is advisable to
carry out solubility test even with solvents considered
benign to natural resin finishes.
Although hydrocarbon solvents will remove
fingerprints and any applied wax coating,
much grime may require a polar solvent to
remove it.
It is possible to clean some surfaces with
water, but certain situations should be avoided.
Aqueous solutions should not be used where
damage to the surface means that water may
penetrate to the ground or substrate. Water-soluble
size on the surface, although rare in
japanning, would also be removed by this
approach to cleaning. Water should not be
used on japanned metals since the water may
accelerate the corrosion of the underlying
metal.
If the surface is sound and insoluble, cleaning
with water is not difficult. Moisture can be
applied using a swab dampened with deionized
water or saliva. Moisture should be
applied to the surface only and thus the swab
should be damp but not dripping wet. The surface
should be dried immediately with soft cotton.
Extended exposure to moisture may cause
the japanned surface to bloom. The risk of
bloom increases with the degree of ageing of
the varnish and as the pH of the cleaning solution
rises. Some very degraded natural resin
surfaces may be partially soluble in water with
a pH of only 8–8.5, a fact that has been
exploited in varnish removal treatments
(Wolbers et al., 1990). The principles of aqueous
cleaning, including the use of pH buffers,
are discussed in section 11.5.
An alternative to wet or solvent cleaning is
mechanical cleaning with abrasives. Fine abrasives
can only be used on an undamaged,
robust and relatively smooth surface. The
methods outlined would not be the conservator’s
first choice but can be used in some cases
when the use of solvent is not possible. A fragile
surface may be lost due to the inappropriate
use of abrasives. Using this technique will
remove not only the dirt but a thin layer of the
varnish as well. This method should be confined
to circumstances where the varnish on
the surface is not original. The disadvantages
of using abrasives are that fine powder can
become embedded in the craquelure, and a
patchy appearance may result if abrasives are
used on an uneven surface. This is often found
in situations where the surface has previously
cupped and then been consolidated. In such
cases the raised areas will be abraded while
the pits remain filled with discoloured varnish.
There are a number of different methods for
the use of abrasives. Fine powders can be
applied in mineral spirits or a non-drying oil.