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generic specifying


Architect's memo 79: February 2005

Once upon a time the world was a simpler place than it is today; technology was limited with the consequential constraints on choice; paint was, well, just paint and an architect could generally specify by generic type and be reasonably assured of getting what they wanted without appearing to favour any particular manufacturer.

Different stimuli foment change; market pull, technical push, societal pressure and, more and more, health and safety concerns. When a species as innovative as ours, armed with our exponential increase in knowledge, confronts a need for change, you can bet your bottom dollar that the approaches (and possible solutions) will be many and varied.

No so long ago, zinc chromate ruled the world of anti-corrosive pigments. So powerful was it that one could make an anti-corrosive paint out of just about anything as long as one put enough zinc chromate into it! Then zinc chromate became recognised as a human carcinogen and the scramble for replacements began. One of about a dozen different technology streams developed was zinc phosphate. Focusing on one of the many zinc phosphate producers in the world, they realised that simple zinc phosphate had many short-comings, which spawned eight second generation products and a further five third generation products.

Not one of this wide range of products can be singled out as omnipotent, each having certain strengths in different paint binders, over different substrates and in different exposure regimes. Generic specification in this particular area is simply not feasible.

The area of colour can also be a minefield. There are some simple colours like red and yellow oxides (ochres) that have not changed in decades and can be relied upon to deliver consistent colour performance. There are, however, about forty classified bright yellow pigments and about sixty organic reds. Whilst not all of these are used in paint, and some have distinctly different shades, nonetheless there is a high possibility of having yellows, oranges and reds of almost identical colour based on totally different pigments.

The pigments within these groups differ on the basis of strength, durability, UV resistance, hiding power, solvent resistance, lime resistance - the list goes on. The performance of the colour is inextricably linked to these properties of the pigment.

Assurances of performance can only come from personal experiences (or that of colleagues) or from a close and trusted partnership with the colour supplier.

The above are just two examples in a plethora of widely divergent technologies used in the paint industry. A book could literally (arghh - what sort of pun is that?!) be written on the different acrylic binders available but we don't want to belabour the point. However, the simple specification of a 'low sheen acrylic' could result in inappropriate products being applied as this generic description could include anything from very simple thermoplastic materials to high performance low sheen enamels. Performance of these materials through a range of properties such as stain resistance to behaviour in a fire situation can differ enormously.

The obvious differences in, say, appliances are such that specifying by brand is accepted without hesitation. The differences engineered into paint are not nearly so obvious but are nonetheless present and important. Suffice to say that generic specifications are becoming as anachronistic as memo writers scratching away on a yellow pad with a pencil!


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