Conservation & Heritage Issue 50 Winter 2025/Spring 2026 - Flipbook - Page 43
Nature Knows Best
Architect Kevin Davies provides some insight into the benefits of using traditional
Swedish linseed oil paint.
Part 2
Above, Field of Flax in flower
Alkyd paint (artificial oil paint) – linseed oil is replaced with
synthetic alkyd resin oil then dissolved in petrochemical
solvent. Polyurethane paints and varnishes contain urethane
binders or urethane-modified alkyds. Whilst the alkyd resin
oils are often derived from plant products (the fatty acids may
come from safflower, sunflower or fish oils) the solvents that
evaporate as the paint dries are harmful. Toluene, benzene,
acetone, paraffin oil (white spirits) and ethanol contain high
levels of volatile organic compounds (VOC’s) and exposure
to high concentrations has been the cause of ill health among
painters for decades. Most of us will have at some time
experienced the general narcotic effects of using solvents –
headaches, drowsiness, dizziness & nausea. The dangers of
long-term exposure to solvents can be much more serious.
In Denmark a chronic cerebral syndrome is referred to as
‘painters’ dementia.’ All manufactured decorate coatings
must comply with VOC limits. There are many who believe
that these limits are still too high, the paint industry giants
were certainly reluctant to change and effectively lobbied
government to ensure that some of their products (albeit
modified) could comply and profits could be maintained.
The VOC limit for solvent-based oil paint for wood is 300
g/l, traditional linseed paint will contain less than 18g/l.
The Introduction of Modern Paint
Since the 1940’s the paint industry moved away from
traditional (linseed) paint production in favour of chemical,
petroleum and solvent based paints (Alkyd & Acrylic). Paint
manufacture became a high-tech industrial scale process,
think large carbon footprint, which continues to this day.
Vast quantities of paint could be made at relatively little
expense, thanks to the use of fossil fuels. We are now in a
period of ‘green enlightenment’, it’s unlikely we would have
chosen the petrochemical and paint industry giants solutions
if they were proposed today, even with the marketing
departments telling us otherwise.
Acrylic and Alkyd paints have a dry matter content of around
40% and 55% respectively, the remainder is solvents, and
these evaporate as the paint dries. So, about half the ‘paint’
in the pot goes into the atmosphere, not on the surface being
painted.
Coverage rates for the Alkyd and Acrylic paints are between
10% & 40% lower than for the linseed paint, meaning you
need more paint to cover the same area. Lower coverage rates
combined with the necessity to apply primers and undercoats
(topcoats do not stick to wood) result in higher overall costs
for the application of the modern paint system.
I
Conservation & Heritage Journal
41
I
