Vegetable tanning extract powder

01

Compare tannin content, moisture and pH — and the method behind them

ASTM D6401 determines how much of an extract's soluble solids are tannins and how much are soluble non-tannins: tannins are the portion of soluble solids absorbed or bound by a prepared hide powder, non-tannins the portion that is not. It applies to liquid, solid, pasty and powdered extracts, and its results depend on solution temperature, the kaolin layer on the filter paper, the run-out rate and the hide powder, so the method has to be followed exactly. [5] Silvateam states its tannin contents by the filter method and gives pH at 6.9 °Bé; its powders list chestnut at 76 ± 1.0% (astringent) or 72 ± 1.0% (sweetened), quebracho at 72 ± 1.5%, myrobalan at 70% minimum, gambier at 50% minimum and tara at 48% minimum, with humidity at 8% maximum for chestnut, quebracho and myrobalan, 12% for gambier and 13% for tara. [1]

Tanac's WEIBULL natural mimosa extract datasheet lists 72 ± 2% tannins (77% ± 2 on dry basis) by the filter method on an analytical solution of 0.4% w/v pure tannin, moisture at packing of 6.5% maximum, pH 4.5–5.0 in a 20% w/v solution, Lovibond colour of red 1.1–1.3 and yellow 2.5–3.0, anionic character and good electrolyte stability; it is a dust-free, hygroscopic light-beige powder soluble in cold water. [3]

A 2024 open-access study of a chestnut extract and a sulphited quebracho extract supplied by Silvateam measured tannin and insolubles by ISO 14088:2020 and reported: chestnut 40.2% tannin, tannin-to-non-tannin ratio 4.6, moisture 5.0%, pH 3.5, ash 0.98%; sulphited quebracho 79.4%, 5.2, 5.3%, pH 4.6, ash 6.52%; insolubles were below 1 mg/mL in all extracts. Purified fractions reached 83.1% and 87.8% tannin with ratios of 8.3 and 11.2. [4]

Editorial calculation: Tanac's 72% as packed divided by (1 − 0.065) for 6.5% moisture gives about 77%, the dry-basis figure on the same sheet — so compare offers on one basis and ask which method (filter or other) produced each number.

Give the supplier the plant source and type you need, tannin content with method and basis (as is or dry), non-tannins or tannin-to-non-tannin ratio, insolubles, moisture at packing, pH with solution concentration, colour (Lovibond or visual), ash, the leather type and process (pit, pit-drum, drum, retanning), package and quantity.

02

Choose the plant source, solubility type and dosage

Silvateam describes quebracho (Schinopsis balansae and S. lorentzii) as a South American tree harvested after at least 80 years' growth and sold as spray-dried moistened powder. Cold-soluble grades are sulphited to turn phlobaphenes into soluble tannins and offer rapid penetration, high tannin content and relatively low non-tannins; semi-soluble grades penetrate more slowly, fill more and contain a small quantity of insolubles. Its ordinary grade gives the rosy quebracho colour, another grade a yellowish shade, and a decolorized semi-soluble grade a pale rosy colour. [2] Silvateam adds that "Tara tannins are mainly used in automotive upholstery" and "Gambier extracts are mainly used for full grain and fine valuable articles", says myrobalan gives a uniform colour and soft touch, and lists astringent chestnut at pH 3.5 against sweetened chestnut at pH 4.5. [1]

Tanac obtains its mimosa extracts from the water extract of black wattle bark and recommends, for vegetable tanning, 25–30% on limed weight for vaqueta, 35–40% for soleta, 38–42% for sola fachete and 45–50% for sole leather (sola); for retanning, 4–8% on shaved weight for nappa, 8–14% for semi-chrome, 15–25% for vegetalizado (vegetable-retanned) leather and 5–10% for nubuck. It supplies 25 kg bags or pallets of up to 2 t, notes that colour can change slightly one year after manufacture, and gives a 2-year shelf life in dry, ventilated, closed storage away from sunlight. [3]

In the 2024 study, pelts were tanned in a drum with 100% water, NaCl at 7 °Bé and 40% tanning agent on pelt weight, run overnight to pH 4–5; chestnut extract was brown, sulphited quebracho red-brown, and the purified fractions yellow, cutting wastewater COD by 13.5% and 19.1%. [4]

Editorial calculation: 1,000 kg of limed pelt tanned for sole leather at 45–50% takes 450–500 kg of extract; at 72% tannins that delivers about 324–360 kg of tannin.

03

Powder and liquid grades across six plant sources

The reviewed sources show powders from chestnut, quebracho, mimosa, tara, gambier and myrobalan, and liquid tara and gambier grades at 27% and 28% minimum tannin with 60% and 65% maximum humidity. [1] When requesting quotations, ask each supplier for a certificate of analysis per lot with the tannin method named.

04

Tannins, non-tannins, insolubles, moisture and ash in an extract powder

The tannin/non-tannin split is defined by ASTM D6401's hide-powder test; moisture runs from 6.5% maximum at packing for Tanac's mimosa to 13% maximum for Silvateam's tara powder. [5] [3] [1]

05

Tannin content, moisture, pH, solubility and shelf life for a tanning extract order

Particle size, bulk density, sulfated ash and heavy metals are not stated in any reviewed source, so those rows depend on the supplier's certificate of analysis.

06

Send the source, grade and dosage together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Source: [mimosa; quebracho; chestnut; tara; other]
Type: [cold-soluble; semi-soluble; astringent; sweetened; clarified]
Tannins: [%; method; basis]
Moisture, pH: [% max; pH at concentration]
Colour: [Lovibond or visual]
Use: [tanning on limed weight; retanning on shaved weight]
Packaging: [25 kg bags; pallets]
Quantity: [tonnes]

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