Natural tannins for leathers that live and change over time
Quebracho colorado (Schinopsis balansae and Schinopsis lorentzii), commonly called quebracho is an evergreen tree that grows wild in South America, mainly in Argentina and Paraguay, in dense sub-tropical forests which also include a variety of other trees and vegetation. It is only after a minimum of 80 years growth that quebracho is mature enough for the extraction. Silvateam respects the environment and the strict local regulations for the extraction of condensed tannins. Quebracho extract is commercialized in the form of spray-dried moistened powder.
The name is due to its hardness, being derived from two Spanish words, quebrar and hacha, meaning the axe breaker. In fact, quebracho has been used locally for posts, telegraph poles, bridge timbers, railway ties, paving blocks and for any construction where great durability is desired.
Cold soluble and semi-soluble extracts
Quebracho extracts are classified according to their solubility in two main categories: cold soluble quebracho extract and semi-soluble quebracho extract.
Cold soluble quebracho extracts
Are obtained by subjecting the ordinary extract to a sulphiting process which transforms the phlobaphenes into completely soluble tannins. Cold soluble quebracho extracts are the most universally known and used types. These extracts have very rapid penetration, high tannin content and a relatively low percentage of non-tannins. The rather low acid and medium salt content characterize them as mild tanning extracts (low astringency).
The semi-soluble quebracho extracts
Are special types obtained by a partial solubilization, combined or not with a decolorization treatment. These extracts penetrate less rapidly than the soluble types but have a greater filling power. They contain a small quantity of insolubles, while the tannin and non-tannins contents are more or less the same as those of soluble extracts. The pH corresponds to the isoelectric tanning point.
Natural tannins, real leathers
Today, quebracho extracts are used to produce all types of leather (bags, saddles, belts, upper shoes, garment, car seats), but its qualities are highlighted when used to produce natural, full vegetable leather, like harnesses and vacchetta.
Cold soluble quebracho extracts can be blended either among themselves, or with other vegetable extracts, phenolic syntans, naphthalene and phenol-naphthalene syntans and they can be used in all stages of vegetable tanning (rapid, semi rapid and pit drum), in re-tanning of chrome tanned leathers where good fullness, roundness, and buffability are required.
Indusol and Indusol ATO impart to the leathers the typical rosy color of quebracho, Indusol ATG gives a yellowish shade.
Due to their filling properties, the semi-soluble extracts find their main use in the tanning process of very empty vegetable crust leathers and of skins which have been dewoolled by sweating or with enzyme processes. The second most important application is in the retanning of chrome tanned shoe uppers or of vacchetta type and saddlery leathers when the raw hides are rather empty. The semi-soluble quebracho extracts are also indicated for the production of burnish leathers, which will darken easily upon friction.
Indusol ATS imparts a typical rosy color of quebracho to the leathers; Indusol ATD is a decolorized extract and it gives a pale rosy color.
Since quebracho extracts can be used in many and varied applications, according to the kind of leather to be produced and the tanning / retanning systems adopted, a complete explanation and instructions will be provided upon request.