Series editors' preface - Wood Tools

may cause irreparable damage. Applications
which result in a deposit on the surface of an
object will kill adults as they emerge, whilst
insecticide in solution may be injected into
wormholes to kill larvae and act as a residual
treatment. It has been suggested that such
contact or ingestion poisons provide protection
for an extended time and therefore are
more desirable than curative methods. This
may not be true and it may not be desirable.
The effectiveness of these liquid toxic materials
largely depends upon the penetration rate
of the liquid and on whether the entire piece
is being treated or just a part of it.
When using insecticides it is the responsibility
of the conservator to be fully aware of the
hazard presented and to take adequate
precautionary measures. These may include
the use of suitable gloves, mask and coat and
maintaining a high standard of personal and
workshop hygiene. It is essential when using
insecticides to follow the guidelines for safe
use set out by the manufacturer. Ware (1988)
and CCI Technical Bulletin 15 (1992) list
numerous insecticides and pesticides which
have been used to treat organic materials.
Insecticidal treatments have been used since
the nineteenth century to control insect infestation.
An overview of historical materials and
methods is given by Unger et al. (2001) and
Schiessl (1984). As side effects which are
harmful to humans become known, insecticides
are taken off the domestic market. An
example of this was the insecticide lindane
(hexachlorocyclohexane), which was widely
used from the 1950s through to the early
1980s. Although an effective insecticide, its
high vapour pressure resulted in it subliming
off treated material over time. Concerns over
long-term toxic and carcinogenic effects
resulted in its withdrawal. Synthetic
pyrethroids have been widely used to treat
anobium infestations since the mid 1980s
because they combine low mammalian toxicity,
highly insecticidal properties which allow
low dosage treatments, are odourless and do
not stain (Pinniger and Child, 1996). However
some research has connected their use with
increased incidence of cancer (Nicholson,
1997). It may be necessary to label objects
which have been treated with a residual pesticide
to avoid any potential health and safety
hazards for future handlers or conservators.
General review of environment and deterioration 271
Dichlorvos vapour (2,2, dimethyl dichlorovinyl
phosphate) from insecticidal strips has
proven to be effective against emerging adults.
Such strips are particularly suitable for storage
or display areas which are comparatively
undisturbed and allow the slow and sustained
release necessary for pesticidal effectiveness.
Strips should not be placed in contact with
objects. In the presence of moisture dichlorvos
hydrolyses readily to form acidic
compounds. At high RH (>70%) it is potentially
damaging to metals and may cause
natural resins, glues and plastics to become
tacky and acid and disperse red dyes are also
vulnerable to damage. Dichlorvos has a short
term exposure limit (STEL).
Rentokil plc have developed a method
which deposits a very low concentration of
boric acid on exposed timber. This treatment
is usually effective over a period of several
years but will not prevent damage by larvae
which will remain active until they emerge as
adults and are killed.
Fumigants Toxic gases that have most
commonly been used as fumigants for insect
infestations in furniture include methyl bromide,
ethylene oxide and phosphine, although
sulphuryl fluoride, hydrogen cyanide, carbon
disulphide and ethylene chloride have also
been used. These materials have good
penetration and are effective in treating complex
furniture constructions and upholstery.
They are not persistent, that is they do not
prevent reinfestation, but they act quickly and
have a high kill rate on all stages of the insect
life cycle. The risk of staining is low compared
to the use of solvent-based insecticidal formulations
and the use of adhesives and coatings
can proceed immediately after use. They have
provided good results as a first line attack.
However, they are highly toxic to other organisms,
including people, and require special
apparatus and fully trained and qualified
personnel to be used safely.
There is a growing body of evidence that
such materials are damaging to the environment
and in some case to the objects being
fumigated (Burgess and Binnie, 1991; Dow,
undated; Florian, 1987; Koestler 1993). Methyl
bromide for example has contributed to the
destruction of the ozone layer and may damage
some materials as it weakens chemical bonds