Abstract

Some of the literature applicable to low float techniques and elevated temperatures is reviewed. An experiment using calfskins is described comparing a convention al tannage with a low float tannage in which the chromium was fixed by application of heat and addition of alkali during tannage and hot washing after shaving instead of neutralisation. A second experiment compares the conventional tannage with a low float tannage in which chromium was fixed by heat during chroming with out the addition of alkali, applying hot washing after chroming and again giving a hot wash after shaving instead of neutralisation. Comparisons are made between full chrome and chrome retanned leather. Weight yields, thickness, grain strength, extensibility, fullness, firm ness, tensile strength and shrinkage temperature were determined. Results of the first experiment indicate that the short float method gave adequate chrome contents without tedious additions of alkali at the end of tannage and without giving the usual ageing period. The maximum temperature reached was 50°c. The leather was stronger than that made by the conventional method but slightly thinner and firmer. Differences were smaller after a retannage. In the second experiment when no alkali was added during the short float chroming at elevated temperature and when chrome was fixed by hot washing at 60°c, the leather showed an increased chrome content and shrinkage temperature but had been weakened. it is concluded thit elevated temperatures during chroming and hot washing can be used to save the time taken for basification, ageing and neutralising but there is a limit to the temperature used if leather of maximum strength is required. The colours obtained with acid or basic dyes on full chrome and retanned leathers are demonstrated. The methods of chroming con siderably influenced the shades produced. A final comparison is made on retanned sides using sides from 50-59 lb. cow hides suitable for corrected grain leathers. The low float tannage using heat in this case is shown to produce leather with a higher content of C,023r and more mellowness. Grain strengths were similar for both types of tannage and the sides by both types of chrome tanning finished as commercially sound leathers.