red rot n.
A type of deterioration of leather bindings, which occurs as either a brittleness in very old bindings or a powdering of the leather. The powdering appears to affect virtually all leathers, and is apparently influenced by the tanning agents, light, atmospheric conditions and, how frequently the book is handled.
red rot can be treated with hydroxypropylcellulose – known as Kugel G- a non-ionic cellulose ether used as a consolidant. Mixed with isopropanol and sold to treat red rot under the trade name Cellugel®. It penetrates the surface of leather and consolidates the leather substrate by depositing a thin film which provides resistance to atmospheric conditions but does not darken or discolor leather surfaces. It will not stain other materials it comes in contact with.