Series editors' preface - Wood Tools

Plastics and polymers, coatings and binding media, adhesives and consolidants 167
time periods, the proportion of esters and free
fatty acids has decreased and the proportion of
hydrocarbons has increased. Ceresin, a dazzling
white, odourless plastic and non-crystalline
wax with a melting range of 65–80 °C is
sometimes used as a substitute for beeswax.
Paraffin waxes, the most important group of
mineral waxes, are obtained by distillation of
shale oil, lignite and petroleum. These bluishwhite,
translucent, highly inert waxes consist of
mixtures of saturated hydrocarbons having the
general formula C nH 2n+2. They are available in
a wide range of well defined melting points
from 48 °C up to 62 °C. Those with higher
melting points are harder, heavier and less
crystalline. Higher molecular weight hydrocarbon
fractions that tend to produce very small
crystals during the preparation of paraffin
waxes are designated as microcrystalline wax.
These waxes are tough, have a high melting
point (e.g. 90 °C) and are produced with a variety
of hardness properties from hard to very
hard. Advantage is taken of these properties
and of their clear (white) colour and inertness
in the production of coatings having a high
resistance to moisture and gases (e.g.
Renaissance Wax ® ) for decorated surfaces and
for metals and in their use as matting agents in
wax resin varnish compositions (Plenderleith
and Werner, 1971; Larson, 1979; de Witte,
1975).
Commercial products
Most proprietary furniture paste waxes are
based on beeswax (animal) with the addition
of another higher melting temperature wax
(vegetable) to achieve adequate hardness for
furniture surfaces. They tend to be preferred in
the furniture trade as they have among the best
properties of application, buffing, appearance
and wearability. Pigments or dyes may be used
to colour the wax so that traces of wax left
behind do not become noticeable as they dry.
These colorants rarely impart colour to an
existing finish but they may affect bare wood.
Some products include UV inhibitors designed
to protect finishes from the effects of ultra
violet radiation. Solvents in commercial animal/vegetable
waxes are commonly turpentine,
white spirits or toluene. The more toxic
hydrocarbon solvents such as toluene present
greater health risks in their use (McCann,
1979). Wax polish recipes are given in Chapter
13. The use of waxes in moulding and modelling
is discussed in Chapter 10.
4.7.3 Carbohydrates: sugars and
polysaccharides
Carbohydrates, so called because they contain
only carbon, hydrogen and oxygen, include
simple sugars and polymers of simple sugars
termed polysaccharides. Few simple sugars are
used in object fabrication and conservation but
polysaccharides are encountered in the form of
starches, dextrins, water soluble gums or
mucilages and alginates. Starches are present in
plants in the form of complex granules with no
adhesive characteristics. If starch granules are
cooked they will swell and burst yielding a
water-dispersed colloidal paste with good
adhesive qualities. Starch adhesives are very
polar and wet cellulosics such as paper and
wood well. Japanese woodworkers have used
rice starch extensively but in the West the use
of starch-type adhesives has been mostly confined
to the paper industries. Dextrins are
derived from starches but have shorter chain
lengths. Though extensively used in bonding
paper, they have seen little use in woodworking.
Water-soluble gums include acacia (gum
arabic), cherry gum and gum tragacanth. They
have been extensively employed as label adhesives
and water colour paint binders.
All these materials are relatively weak and
unlikely to cause substrate failure. They have
long to moderate open times, depending on
ambient humidity, with excellent machinability
and no significant health hazards. They vary in
colour from white (starches) to light amber
(plant gums) and show only slight optical saturation
depending on concentration. The
chemical stability of starches is excellent and
that of plant gums is fair to good. Their resistance
to moisture is poor and bonds made with
them are easily reversible using water.
Alginates
Alginates are polysaccharides extracted from
various species of marine algae which form
hydro-colloidal gels in water quite similar to
those formed by animal glues. Agar–agar is one
such alginate also sometimes called Japanese
isinglass. Their use in moulding is discussed in
Chapter 10.