Aircraft dope (nitrate, butyrate)

http://en.wikipedia.org/wiki/Aircraft_dope

Aircraft dope is a plasticised lacquer that is applied to fabric-covered aircraft. It tautens and stiffens fabric stretched over airframes and renders them airtight and weatherproof.[1]

Typical doping agents include nitrocellulose, cellulose acetate and cellulose acetate butyrate. Liquid dopes are highly flammable; nitrocellulose, for instance, is also known as the explosive propellant "guncotton". Dopes will often include colouring pigments to facilitate even application. The material is available in a wide range of colors.

Dope has been applied to various aircraft fabrics, including Madapolam, but also is used on more recently used man-made polyester fabric.[2] or fabric with similar fine weave and absorbent qualities.[3]