Neptune Watercolor Brushes Neptune Brushes are a true breakthrough for watercolorists. They provide a new level of finesse and control in your painting. After seven years of development, we created our softest and thirstiest synthetic hair ever. Neptune brushes hold a reservoir of water, delivering oceans of color with each stroke. We developed a collection of professional quality synthetic paintbrushes that are more durable and affordable than the natural version and are animal friendly.