Cellulose acid tendering

Tendering Effects. Cellulosic materials dyed with sulfur black have been known to suffer degradation by acid tendering when stored under moist warm conditions. This effect may result from the liberation of small quantities of sulfuric acid which occurs when some of the polysulfide links of the sulfur dye are ruptured. A buffer, such as sodium acetate, or a dilute alkali in the final rinse, especially after oxidation in acidic conditions, may prevent this occurrence. Copper salts should never be used with sulfur black dyes because they catalyze sulfuric acid generation. Few instances of tendering with sulfur dyes other than black occur and the problem is largely confined to cotton. 

Hydrocellulose. Ci2H220n, mw 342.30. The term has been employed since about 1880 to designate a cellulose which has been weakened or tendered as the result of treatment with acids. It retains water strongly. Hydrocellulose is not a single substance but a mixture of hydrolyzed products less complex than cellulose itself and more or less related to it and to glucose (Refs 4 6)... 

Recent approaches directed toward preventing oxidation of cotton cloth included using accelerated aging of alkaline-treated cotton cloth for neutralization of acidic, oxidized, cellulose decomposition components that in cellulosic textiles and in paper are responsible for age tendering and yellowing. Conclusions regarding the relative effectiveness of treatments at room temperature were based on results of treatments at one elevated temperature (8). Predictions of long-term effects of these treatments are unknown (9). 

Sulphur dyes and in particular the black shades are liable to cause tendering of cellulose, on storage. The cause is the gradual oxidation of a portion of the sulphur to sulphuric acid. The work of Zanker and others on this... 

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