Highly Substantive, Anionic, Direct Dyes, Specially Developed for the Paper Industry. They are Particularly Suitable for Dyeing Paper and Board in the stock and at the size press. Advantages of PAPTRON Liquid Dyes: High affinity, giving high color yield, clear backwaters and the possibility of adding the dyes late in the stock flow system. The liquid dyes are particularly suitable for continuous addition. Good Bleedfastness. Brighter Shades.