Controversy certainly exists in the area of artists wanting to
use archivable products in their work as well as being attracted
to the economies of mass produced house paints. A major hurdle
is immediately imposed by the fine art suppliers, damning such
products as 'ordinary house paint'. Whilst lower quality products
do exist, high quality, modern architectural coatings are, in
fact, quite extraordinary products.
The principal ingredients in all paints are binders (which form
the films), prime pigments (which give the colour and opacity)
and extender pigments (which contribute to build, porosity and
surface roughness). Although there can be interaction between
some reactive pigments and extenders with the binder, durability
of an undercoat is predominantly the domain of the binder.
Binders used in modern architectural coatings consist of polymers
of very high molecular weight (read stable) with little to no
reactive groups (read stable again). Major polymers used are P.V.A's,
styrene acrylics and pure acrylics. P.V.A's tend to be somewhat
water and alkali sensitive; styrene acrylics are slightly prone
to yellowing (but nothing like linseed oil) and acrylics are pretty
These polymers are not single entities but a series of materials
ranging from soft, highly flexible binders through to hard and
brittle. Paint manufacturers select polymers on the basis of the
job it needs to do. For example exterior timber coatings require
a much more flexible binder than does a concrete coating.
In undercoats, the amount of pigment and extender that is combined
with the binder has a powerful effect on the final properties
of the film. For the same binder, increasing amounts of pigments
and extenders lead to easily sanded films with high levels of
porosity. This porosity can be very pleasant to work on with water
colours where penetration can occur even with typically non-staining
colours. Highly pigmented undercoats will generally be less flexible
and more likely to damage if a finished canvas were tightly rolled.
As one increases the level of binder, the porosity drops off
and the undercoat becomes more suitable for use under acrylics.
Flexibility and toughness increases. Further increases in binder
produces even tougher films which are highly suited for use under
A word about surface characteristics and adhesion! It is generally
intuitively felt that smooth surfaces must be more difficult to
adhere to than rough ones. In the case of acrylic (including styrene
acrylic and P.V.A) undercoats, this is not the case. The surface
nature of these polymers is such that they are extremely receptive
This is not to say that the surface characteristics are unimportant;
they are indeed important but not for reasons of adhesion. Very
smooth surfaces can allow a loaded paint brush to skid across
the surface impacting upon the artist's control. Too coarse a
surface may demand too much paint, also impacting on control.
The ideal surface is uniform with a very slight roughness, which
presents a surface that accepts paint in a reasonably predictable
Modern architectural undercoats may not be traditional (but then
when was gesso last made from rabbit's skin oil?) but they do
offer sound, stable, archivable bases for the artist. It is difficult
to imagine them degrading in a benign interior environment.
This particular article has been somewhat 'broad brush' and we realise that it may well raise questions - questions that we would love to respond to. So if you have any questions or suggestions of further information you would like to see, please let us know.