Persuaded by at least one manufacturer's glossy brochure that synthetic brushes were nearly as good as sable, I devised a simple (non-scientific) test that ought to allow direct comparison of the results: I would charge up each brush in turn with paint, and paint a line across a piece of watercolour paper. By labelling each stripe, I would know which brush had created it, and I could compare the lines/stripes with each other to see how the brushes had performed. The unscientific parts of the trial would be that I would not measure how much paint each brush took up, nor could I be sure that I was using the same pressure on each brush to paint the line.
Since I already had several different makes of brush in size 6 round, and further examples weren't going to cost me silly money for what might be a one-time use, I settled on size 6 round for this experiment. As the image above shows, I used a Cotman series 111, a Pro Arte Prolene Plus, a Winsor & Newton Sceptre Gold II, a Ken Bromley Artists' Value Profile (identical to a Pro Arte Prolene), a Pro Arte Connoisseur, a Daler-Rowney Aquafine, and a Daler-Rowney System 3. The paper I used was Ken Bromley Practice Paper (apparently made by Fabriano and excellent value for a rag paper). I had an old 21 ml tube of Winsor & Newton Cotman Hooker's Green Dark, so I had no qualms about mixing up a generous quantity of paint for the test.
substance used to keep the hairs together before sale, and gave them a couple of shakes to remove most of the water. I took a 1/16 sheet (5.5 by 7.5 inches) of paper, and using it in landscape, used an HB pencil to write the name of each brush in the left margin -- spaced about 3/4 inch apart. Now I could start painting. Using each brush in turn in the order on the paper, I swirled it around the palette of Hooker's Green Dark until it was charged up with paint, and then painted a horizontal stripe on the paper starting at the left hand edge under the writing. I then picked up the next brush in the list and repeated the exercise, until I had run out of brushes to test.
Once the watercolour paper had fully dried, I was able assess the results, and compare the stripes. After some deliberation, I rated the stripes from 1 to 7, with 1 being the best, and 7 the worst. Things I looked for were evenness of colour along the length of the stripe, consistency of stripe (no pale horizontal bands), and colour the full width of the paper. As can be seen from the image above, first place was awarded to the W & N Sceptre Gold II, with the Pro Arte Connoisseur coming second. An impressive third place finish went to the W & N Cotman, and the Daler-Rowney System 3 brush ranked in fourth place. Fifth, sixth, and seventh places went to the Pro Arte Prolene Plus, the Daler-Rowney Aquafine, and the Ken Bromley Artists' Value Profile respectively.
A couple of observations. Most of the pure synthetic brushes displayed the (apparently known) tendency to unload their paint at the beginning of the stroke, resulting in a darkish blob to start and a failure to produce an even stripe on the right side of the paper. The Cotman brush behaved least like this, which was why it was awarded third place. Secondly, I have seen a recommendation somewhere on the Internet that a synthetic brush size should be two sizes bigger than its sable equivalent, to compensate for the difference in performance. As can be seen in the image of the brushes, the two Daler-Rowney brushes on the right have longer hairs, and are indeed closer in size to other manufacturers' No. 8 rounds. Should I adjust the scoring to account for this? Oh well, I did say this wasn't scientific!
For actual painting, I alternate between Sceptre Gold II and Prolene Plus, as these are the brushes I have most examples of at present. I find the Sceptre Gold II brushes better for watercolour glazing techniques.
