Dr. Ph. Martin's Pen-White is perfect for fine writing, and was made to be used in a technical pen with a tip of at least 3x0 (0.25 mm), airbrush, or a brush. This pigment based and archival product delivers the same brightness and permanency of traditional watercolors in tubes, but is much more versatile and easy to use. It will also adhere to a variety of surfaces that include film and acetate-type material. The color is incredibly opaque and can cover dye and marker color and is not waterproof. Comes in a 1oz glass bottle with a dropper-top.