As every book, article and website tells you, expensive watercolour brushes made from sable hair hold more paint than those made from synthetic fibres. Even the late and great Mark Gottsegen, Professor at the University of North Carolina, in his wonderful book The Painter’s Handbook, included this same statement.

I was rude enough to ask how much more, and to see the figures. I was surprised to discover – as far as I can tell – that no one knows how much paint is carried by any brush, and no one has made figures available to support the claim.

So I set out to develop a test method which would be sufficiently reproducible, sensitive, and meaningful that it can be used to assess the paint delivery capacity of artists’ watercolour brushes. This series of articles presents details of the method, results that I have obtained, and some fascinating insights which the results provide. Inevitably testing takes time, and I am still working through the dozens of brushes that I have. But for the moment I thought that you might be interested to read some of my most important conclusions.

There have, of course, been some previous attempts to test watercolour brushes in this way. A few people have tried charging brushes with a colour wash, and measuring the area which they have managed to paint. Unfortunately there are many problems in trying to do that, which make error and variability too high to enable meaningful comparison. This may be why there does not appear to be any national or international standard for the ‘performance’ of brushes in this way.

However I think that we need more and better information. Given that, for decent quality watercolour brushes, there is a tenfold or greater range in price for any given size, the time has surely come to make more informed choice.

Looking at the online prices quoted by my favourite online retailer Jackson’s, for a size 30 round, you can pay as much as £313.91 for a Da Vinci Maestro Tobolsky Kolinsky Red Sable Series 10, or as little as £48.00 for a Princeton Synthetic Sable 4050. For a size 12 round, you can pay as much as £83.00 for an Isabey Pure Kolinsky Sable Series 6228, or as little as £4.80 for a Daler Rowney Aquafine Watercolour Brush AF85.

There are lots of questions that I would like to be able to answer, besides the most obvious as to whether sable brushes are worth those high prices. For washes, there is an even wider choice of hair and brush, including squirrel mops, and broad synthetic flats. How do they compare, and against the classic sable rounds? How does the paint capacity of a brush change with age and wear? I am sure that you can think of many others too.

In this first article, I would like to address the two most important questions, which set me on this course.

1. Do expensive sable brushes deliver more paint to the paper than cheaper synthetics?

Yes.

To compare typical round brushes in size 12, a full charge of paint in synthetic hair will deliver wash to cover around 90 to 130 square cm of paper; in sable, you should expect the wash to cover around 250 to 330 square cm of paper. Thus a size 12 sable is almost guaranteed to outperform a size 18 synthetic, and comes close to the performance of synthetics in sizes 24 and 30 – which are huge brushes in comparison.

The difference between paint delivery in comparable brush sizes is so great that no statistical analysis appears necessary.

2. How do sable and synthetic rounds compare in terms of cost-benefit (as regards paint delivery)?

Sable brushes do deliver more paint to the paper, but they do so at significantly greater cost.

For each £ (or roughly $ or €) that you spend on a brush, you can expect a size 12 sable to cover 5 to 10 square cm; for each £/$/€ that you spend on a synthetic-haired brush, you can expect sizes 12 to 30 to cover 10 to 30 square cm. One of the best performing brushes that I have tested so far is a synthetic-haired size 24, which consistently covers 450 to 500 square cm of paper at the remarkably low cost of £16.52, that is around 28 square cm per £/$/€.

I hope that gives sufficient food for thought, and whets your appetite for the next in this series, where I will detail my test method.