Leather Dyeing
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Long before the advent of synthetic dyes, haematine, fustic, pcachwood and other natural dyes were widely used to dye leather along with mordants like aluminium, copper, iron, tin, ( titanium al1d chromium. For examplc, haematine with iron 1 produced a rich black colour.
When syntl1etic dyes like basic dyes wcre introduced, these dyes largely replaced the natural dyes. Basic dyes are prized for the vpry full, rich and powerful shades they produce on leather. Because of the very compact structure of leather, penetration of the dye in the interior of leather does not take place with these dyes and hence they produce srurface dyeing.Since leather is made up of proteins, it can be dyed with acid dyes. The dyeing,is done in the presence of formic acid to fix the dyes. When the dyeing is started in the presence of ammonium hydroxide, better penetration of the dye can be obtained and produce level or even shades. Generally acid dyes are used to dye light shades on leather. They do not give the fullness of shades produced by basic dyes.
