Analysis of variation of the skin substance with the application of different acids in the pickle stage in Ecuadorian serrano bovine leathers

A chemical analysis was carried out to determine the content of skin substance in different leather samples prepared using several acids in the pickling stage. Ecuadorian bovine skin was utilized. It went through the tanning processes until reaching the pickling stage in which three treatments employing sulfuric acid, formic acid and oxalic acid, respectively, were applied. Later, tanning was applied, wet blue samples were obtained and their contents of skin substance were measured by means of AST D2868-17 rules. Results were verified through a statistical analysis using Infostat software. After post tanning stages a dyed leather was obtained upon which physical tests of tension resistance, elongation percent and lastometry as well as sensorial essays of feeling, softness and swelling were executed. The treatments produce results of skin substance from every leather area, that is, head, loin and backside. It is found that the sulfuric acid pickling features the highest content of skin substance (72.63%) followed by the formic acid pickling (70.94%) and the oxalic acid pickling which has the lowest amount of skin substance (65.04%). In order to validate the results, a statistical analysis was performed which confirms the chemical analysis. To ratify which one was the best treatment, a comparison based on the properties of each acid was made. The formic acid was confirmed as the most appropriate since it differentiates from the sulfuric acid due to the skin substance content by complying with the required parameters of elongation (15.89%), and softness/swelling (4%). On the other hand, oxalic acid produced lesser quality results.