catechol tans, often obtained from barks, contain usually about 60 per cent.
Tanning materials are divided into two main classes: Pyrogallol, catechol.
These skins are tanned with turwar bark, which contains a catechol tannin.
The other is called the catechol group and is strongly condemned.
It is particularly advantageous to blend judiciously the two main types of material, the pyrogallol and catechol tans.
The tannins are classified into "pyrogallol tans" and "catechol tans," according to the parent phenol.
Generally, the best mixed tannages for solid leather consist of a combination of both pyrogallol and catechol tannins.
Like all catechol tans, the resulting leather darkens on exposure to sunlight.
It is a catechol tan of peculiarly mellow quality and great practical value.
Xanthin and catechol browns are pleasing in appearance, but their effect is less rich than that obtained with potash.
catechol cat·e·chol (kāt'ĭ-kôl', -kōl')