Two- bath chrome tanning

A two bath chrome tannage as outlined earlier is based on the penetration of the skin by dichromate which in turn is reduced by the addition of sodium thio sulfate during the tannage. This results in an in situ formation of trivalent chromium and fixation of this chromium by the skin two bath tannage also results in the formation of sulfur from the breakdown of sodium thio sulfate. The formation of sulfur inside the skin has a filling action and results in certain roundness, a fullness and tightness of grain that is desirable. Two – bath chrome tannage is costly in materials, labor and time the two- bath chrome tannage has disappeared from practical application in side upper leather production in the world but is still used in the production of some light leathers, such as glazed kid. The colloidal sulfur aspect of the use of sodium thio sulfate has led some tanners to incorporate thio sulfate into the neutralization process as a part of their normal one- bath chrome tannage.