Series editors' preface - Wood Tools

134 Conservation of Furniture
Table 4.1 Continued
Polymer group, names Date Description and use Simple identification
and trademarks introduced
and
country
Urea formaldehyde (UF) 1926 UK Very hard, amorphous, chemically Difficult to ignite, burns with
terns. Many nineteenth-century moulds for
composition ornaments were made of pitch
mixtures enclosed in a strong frame and
squeezed, while hot and pliable, over an oiled
carving. Gutta percha was also used as a
mould material. Modern synthetic resins can
also be used in this way (see section 4.7.6).
Dental impression compounds have been used
in picture frame restoration to make small
squeeze moulds for the replacement of lost
composition ornament. Commercial mouldmakers
and sculptors have used poly(vinyl
chloride) ‘hot melts’ extensively for large flexible
moulds.
4.1.4 Identification of plastics and
polymers
Knowledge of the history of plastics provides
useful background to their identification.
Mossman (1988) and Braun (1986) provide
simple tests for identifying plastics primarily
based on solubility, heating and flame tests
although additives for plastics are likely to
modify test results (Gächter and Müller, 1985).
The identification of additives in many
instances can be carried out using methods
described elsewhere in this chapter, however
some additives are extremely difficult to identify
directly and can only be inferred by the
modification of properties from pure polymer
or by sophisticated instrumental analytical
techniques.
The increased complexity of polymeric
materials has made their positive identification
resistant thermoset formed by
polycondensation of urea and
formaldehyde. The resin is always mixed
with one or more fillers to make it
suitable for particular applications. Used
for adhesives and mouldings, and, with or
without alkyds in reaction type coatings.,
Normally available in dark, opaque
colours. Chips and powders when cut
Source: Compiled from information in Hall, 1981, Kaufmann, 1968 and others cited in Chapter 4
pale yellow flame with bluish
edges and fishy smell. Selfextinguishing
on removal from
flame. Not affected by
cyclohexane or aromatic
hydrocarbon solvents
correspondingly more difficult. Lebeaux (1989)
has published a book known as the Resinkit
that contains fifty samples of common plastics
along with simple tests for identifying unknown
plastics and comparing them to standards. This
kit is helpful for observing the range of
physico-mechanical properties of commercial
polymers. Urbanski et al. (1977) provides more
advanced methods for identifying plastics.
Though some methods require sample amounts
that may prohibit their use in conservation, the
use of silicon carbide sampling of materials for
examination by Fourier Transform Infra Red
(FTIR) spectroscopy, as described by Martin
(1988), is virtually non-destructive. FTIR
microscopy is now becoming more generally
available. Spectroscopic methods are further
discussed by King (1992). Blank (1988) provides
some simple tests relevant to conservation
issues to help identify classes of polymers in
order to determine proper consolidants and
storage methods. Further information on the
characterization of polymers is given by
Campbell and White (1989) and by Hunt and
James (1992). The identification of polymers
used as coatings and media, adhesives and consolidants
is discussed in section 4.8 below.
4.2 Introduction to coatings,
binding media, adhesives, and
consolidants
Coatings, media and adhesives are found as
normal constituents of most furniture items.