Architects memo no.
85: November 2006
Bacteria that is! These oldest of life forms are also the most ubiquitous.
They will live, not only in all the most obvious places, but also on
top of mountains and in the deepest ocean; in the frozen rocks and ice
of Antarctica to near boiling mud pools in Rotorua. They can live with
or without oxygen and even thrive in atmospheres toxic to humans. And
if life gets a bit too tough, well, they can close down their systems
and go dormant for extended periods.
But are they goodies or baddies? Well they really are a mixture. At
the dawn of life on earth cyanobacter, such as stromatolites, were able
to exist in the nitrogen rich atmosphere of that time and deliver up
oxygen in sufficient quantities that would later create a hospitable
atmosphere for mammals. So let's hear it for cyanobacter!!
There are many other synergies. There are bacteria that live around
the roots of some plants and which are able to convert gaseous nitrogen
to the soluble nitrates that the plant can beneficially use; there are
benign bacteria that live in the human gut which protect us, by sheer
weight of numbers, from other, more malign types; there are other strains
which use a fermentation process to produce energy and pee almost pure
alcohol - which suggests another, as yet undeveloped, synergy with man.
They are a vital part of the carbon cycle; have been used to help clean
up oil spills; are essential to the production of cheese, pickles, wine,
sauerkraut, yoghurt and can be used as miniature biotechnology factories
for the production of therapeutic drugs such as insulin.
There is a dark, pathogenic side to bacterial society, harbouring such
nasties as cause tetanus, typhoid, tuberculosis, cholera et al as well
as sepsis and most food-borne illnesses.
Paint chemists have always had an eye on the small world of microbiology
and have long protected their waterborne products from bacterial spoilage
in the can by the addition of small amounts of bactericides. They have
also been aware that paint films can support the development of defacing
moulds, fungi, algae and dosed their products with appropriate fungicides
and algaecides. These strategies can be looked upon as self-protective
Some years ago a new trait developed, especially in Japan, whereby
the paint surface was looked upon as potentially being bacteriostatic
and providing an actively hygienic surface. These technologies have
progressed to the stage where they are becoming mainstream in Japan,
Europe and the United States.
There are several possible technologies for achieving this but the
most popular are proving to be based on silver. This 'noble' heavy metal
has shown to have bactericidal properties while having no human toxicity.
The supply of biocidal coatings is not without controversy. Some of
the considered arguments against it include: - they could give consumers
a false sense of security; reduce the level of cleaning; lead to the
development of resistant organisms and possibly, by producing a 'too
clean' environment, lead to the development of lower childhood antibody
production resulting in a greater incidence of, say, asthma. There could
also be a legislative backlash if consumers had higher expectations
than could be met in practice.
Resene have taken the position that silver is a useful tool in the
fight against pathogenic bacteria and can make a positive contribution
in rest homes, food processing areas, bathrooms, toilets etc. They are
offering a silver containing option in their premium interior wall coating
Spacecote Low Sheen - for these uses as a useful adjuvant to normal