Paint, varnish, stain and wax - The Ecology of Building Materials - page 409

Table 18.2: continued

Pigment Constituents Comments

Chrome green Lead chromate, lead

sulphate, ferric
ferrocyanide
Zinc chromate, potassium
chromate, ferric
ferrocyanide

Highly poisonous, prepared from a mixture
of chrome yellow and Prussian blue

Zinc green Poisonous, prepared from a mixture of zinc

yellow and Prussian blue

Brown pigments:
Umber Clay containing iron and

manganese

Some is prepared from earth pigment, but
the majority is done synthetically from ferric
oxide
Originally prepared as an earth pigment

Burnt sienna Hydrated ferric oxide,

silicic acid

Black and grey
pigments:
Slate grey

Slate flour Seldom used, can be easily obtained through

grinding and making a paste of the slate
Can only be prepared synthetically
Can be prepared from ilmenite minerals
Prepared from amorphous carbon which
occurs from burning oil and tar products
Prepared by charring different organic
materials, animal bones and wood

Iron oxide black
Ilmenite black
Lamp black

Iron oxide
Iron titanium oxide
Carbon

Bone black organic
pigment

Carbon, calcium
phosphate

pigment pastes as a dispersal agent. These are thought to be considerably
harmful environmental oestrogens, i.e. chemicals that can affect the develop-
ment of a foetus.
Energy recycling of painted products can lead to the emission of poisonous
pigment vapours. Material painted with paints containing heavy metals repre-
sent a considerable pollution hazard and must be treated as special waste. The
same is true of zinc white, whereas titanium white is not a problem as a waste
product.

Other additives

Many other additives are used, depending upon the type of paint and where it is
to be used.

Fillers
These are simple, colourless materials with the primary function of economizing
and spreading the paint, and in some cases of improving the opacity. They also