Query Related To Leather

Q. Specially in cold climate areas spewing occurs on the hide surface of leather for footwear. How can this problem be tackled?

Ans. Technicians define "repus" as a perspiration that solidifies on the hide surface and produces white stains during leather or footwear storage.This perspiration may be caused by : organic substances such as greases, fatty acids and their mineral soaps (calcium, chrome), mineral substances for example sulphate or sodium chlorate, which have not been well washed from the hide at the end of retannage processes in the drum.
To verify the presence of these fats bring a heating source near to the white stain. In case of the presence of fats, this stain will easily melt for fats have a quite low melting point temperature. A flame brought near to the leather flesh side is the first test commonly performed.
If a mark appears on the grain side in the area where the stain has come off, the stain is a fat spew.
White stains may be due to ingredients contained in the fatliquors used.
Not a complete neutralisation or inadequate washing after neutralisation, that is to say a bad fixation of the fatliquors

Cause
The most frequent cause is the excess of natural fats in the leather. It is due to the lack or inadequate degreasing in the drum Storage of leathers in a cool and excessively humid place mould formation.

Prevention
In order to avoid any stains forming due to spewing, it is necessary to degrease, neutralise and wash the leather correctly during tanning and to employ well-known and appropriate products and technology.
Spewing generally occurs after the shoe is manufactured since the shoe is forced into a high temperature oven and this operation tends to facilitate grease perspiration and excessive solidification on the surface.
In fact when cooling, grease can form a typical white layer, even some days after the shoe has been manufactured. The low air temperature and the high degree of humidity facilitate spewing but, of course, only if leather contains inadequate substances.
This defect is easily eliminated by a brush or, even better, by rubbing gently with a dry soft cloth, over the large areas. Unfortunately this problem still tends to re-appear due to the continuous and progressive perspiration.
To solve partially this problem or to eliminate it completely in less difficult cases, we would suggest to degrease the leather with FENICE's speciality DC 1200. Apply then a basecoat filler as a screen and proceed with ordinary finishing.