Aircraft dope is a plasticised lacquer that is applied to fabric-covered aircraft. It tightens and stiffens fabric stretched over airframes and renders them airtight and weatherproof.
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 often include colouring pigments to facilitate even application, and are available in a wide range of colors.
Dope has been applied to various aircraft fabrics, including madapolam, but also more recently on polyester and other fabrics with similar fine weave and absorbent qualities.
Accidents have occurred when dope is not used correctly, for example when mixed with other chemicals, used on the wrong fabrics, or applied to contaminated or improperly prepared surfaces.