Abstract

Full chrome leathers were prepared, using the same total amount of tanning agent for all samples but varying the proportions offered in the initial tannage and in the retannage (after storage). Quantitative measurements showed that those batches which received a low level of initial tannage and a substantial retannage had less colour variation than those given a fuller initial tannage and smaller retannage. The improvement was seen even after dyeing to a medium brown. Only after dark, surface dyeing were colour differences of the batches brought to a similar level. Chrome retan leathers were also made, with the chrome tanning being carried out in either one step or as a low-level initial process with a retannage to the required Cr₂O₃ content immediately before subsequent processing. Batches of skins from the latter method were more level than those from the one-step chrome tanning process, with the improvement still being considerable after vegetable retanning and dyeing to a medium brown. Bleaching, by the use of a proprietary Syntan, only marginally reduced the variation of colour within any pack.