Civil Engineering Reference
In-Depth Information
solvent vapour which can lead to irritation of the inhalation routes and aller-
gies. These emissions can continue after the building is finished. As waste,
these products are normally not a problem, depending partly upon the pig-
ment used.
Cellulose paints
There are two different cellulose paints - one based on normal cellulose paste
and the other on nitrocellulose. The latter is used mainly for varnish and must
contain up to 75 per cent organic solvents and softeners. Paste paint has approx-
imately the same properties as protein glue paint.
Cellulose paints are mainly based on renewable resources from plants. The
products are made from methyl cellulose in a highly-polluting process using sub-
stances such as chlorinated hydrocarbons (CHCs). The production of nitrocellu-
lose requires large amounts of solvents with heavy environmental consequences
in production and in the painter's working environment.
Within buildings these products are not a problem. Painted material can
probably be energy recycled in normal incinerators or dumped on domestic
tips without any problem, with the exception of Nitro-varnish products with
softeners.
Starch paint
Starch paint is based on starch glue (see p. 398) and is mainly used externally on
unplaned timber, usually in the form of rye flour paste. The paste decays over
time and only the pigment is left. This can rub off. To compensate, it is common
to add about 4-8 per cent linseed oil. In damp environments 1-2 per cent green
vitriol is added to prevent any mould attack.
Starch paint is based on renewable raw materials from plants and represents
absolutely no environmental threat, either in production or use. Re-use and recy-
cling of treated materials is acceptable, as is energy recycling. The materials can
normally be composted. The favourable environmental profile can be reduced by
the addition of environmentally damaging pigment.
Emulsion paint
Emulsion paints are waterproof. They can consist of sinew glue emulsified in lin-
seed oil, or casein emulsified in linseed oil and dissolved in water. They usually
produce a good matt surface with only a few strokes of the brush. This type of
