Red rot is a degradation process found in vegetable-tanned

leather Leather is a strong, flexible and durable material obtained from the tanning, or chemical treatment, of animal skins and hides to prevent decay. The most common leathers come from cattle, sheep, goats, equine animals, buffalo, pigs and hog ...

. Red rot is caused by prolonged storage or exposure to high

relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

, environmental pollution, and high temperature. In particular, red rot occurs at pH values of 4.2 to 4.5. Sulfur dioxide converts to sulfurous acid which forms

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

. The peroxide combines with residual

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'' ...

s in the leather to oxidize proteins, creating

ammonium sulfate Ammonium sulfate (American English and international scientific usage; ammonium sulphate in British English); (NH4)2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen a ...

and

ammonium bisulfate Ammonium bisulfate, also known as ammonium hydrogen sulfate, is a white, crystalline solid with the chemical formula, formula (NH4)HSO4. This salt is the product of the half-neutralization of sulfuric acid by ammonia. Production It is commonly co ...

. Red rot is also caused by problems in the tanning or in the bookbinding. In the tanning examples are: sulfuric acid residue, use of contaminated water and incomplete tanning. The bookbinding process can cause red rot when acids and bases are used when coloring the leather. The decay manifests as a characteristic powdering of the leather's surface, along with structural weakness through loss, delamination, and a felt-like consistency. The damage caused by red rot is irreversible. However, its spread, if caused by environmental factors, may be retarded by an application of a consolidant (such as Klucel G) coated with a sealer (such as Renaissance Wax). The progress of red rot can be stopped or slowed with a treatment of aluminium alkoxide solution, which increases the pH value and becomes (in the presence of water) a buffering inorganic aluminium salt in the leather.

References

{{reflist, refs= {{Cite journal , first=Anna , last=Johnson , year=2013 , title=Evaluation of the use of SC6000 in conjunction with Klucel G as a conservation treatment for bookbinding leather: notes on a preliminary study , journal= J. Inst. Conservation , volume=36 , issue=2 , doi=10.1080/19455224.2013.815646 , pages=125–144 , s2cid=194080498 {{Cite journal , first1=Anne , last1=Lama , first2=A. Paula M. , last2=Antunes , first3=Anthony D. , last3=Covington , first4=Jeffry , last4=Guthrie-Strachan , first5=Yvette , last5=Fletcher , year=2015 , title=Use of aluminium alkoxide and oxazolidine II to treat acid-deteriorated historic leather , journal= J. Inst. Conservation , volume=38 , issue=2 , pages=172–187 , doi=10.1080/19455224.2015.1071713 , s2cid=93393173 , url=http://nectar.northampton.ac.uk/11904/1/Lama_Anne_Taylor_Francis_2015_Use_of_aluminium_alkoxide_and_oxazolidine_II_to_treat_acid_deteriorated_historic_leather.pdf Leather Bookbinding Materials degradation