Sanjet BP21 (JS21) Ink Cartridge, White The Sanjet BP21 White Ink is excellent for marking porous and non-porous substrates. The Sanjet BP21 dry time is typically instant to a few seconds but can take longer depending on application and environment conditions. Substrates The Sanjet BP21 white ink offers excellent adhesion on glass, plastic, metal, aluminum, concrete, pipe, glossy boxes, film, corrugated boxes, paper, and many other substrates.