Artist brush makers have recently introduced synthetic mongoose brushes to the market. The synthetic hair in the brushes comes from manufacturers like Toray Co in Japan and Dupont in the USA. Most synthetic brushes are derived from nylon material. The manufacturers dye the orange fibers dark to make them look more like mongoose hairs. An orange brush would probably not sell well.
This raises the question: how will the dyes used on synthetic mongoose brushes hold up in thinners used for oil paint. To answer this question, we set up a test using a popular mongoose synthetic. We suspended the brush in Biobased Artist Thinner for 36 hours. At two points during the process, we pulled the brush out of the thinner and scraped the fibers to see if there were any loosening of the dye pigments. We also stroked the brush on white printer paper to see if there were any colors being dissolved or removed.
At the end of the test, there was no discernible change in either
the color or the physical condition of the brush fibers. Our conclusion
is that the dyes used on synthetic mongoose brushes hold up very well,
and are not affected by long term submersion in Biobased Artist Thinner.