Tanning and Production
Chrome-Tanned Leather: How It Is Made, What "Wet Blue" Means and Why It Suits Jackets
Chrome-tanned leather is tanned with chromium(III) salts in a drum in a day or two. See the steps, what wet blue means and how it changes a jacket.
Chrome-tanned leather is hide tanned with chromium(III) salts, usually chromium sulfate, in a rotating drum. The chrome step takes about a day or two, and the hide comes out greyish blue, a stage called "wet blue". It is the main way leather is tanned today, at roughly 80 to 90% of production depending on the source.
The tannage gives a soft, stretchable leather, which is why it is used for garments and handbags. This page follows the process step by step. For the safety question, see chromium in leather.
This page is part of our guide to leather tanning and production.
The process, step by step
Chrome tanning sits in the middle of a longer chain. The hide is cured, cleaned and prepared first, and finished afterward.
| Step | What happens | Why |
|---|---|---|
| 1. Beamhouse | Soaking, liming, unhairing, fleshing, deliming and bating | Removes hair, flesh and fat, leaving the collagen layer |
| 2. Pickling | The hide is made acidic | Lowers the pH so the chromium can enter evenly |
| 3. Chromium uptake | Hides tumble in a drum of chrome salt solution until it reaches the full thickness | The small chromium complexes fit between the collagen fibers |
| 4. Basification | The pH is raised to about 3.8-4.0 and the bath warms to about 40 °C (104 °F) | Fixes the chromium to the collagen |
| 5. Wet blue | The hide is greyish blue and can be stored or sold at this stage | A trade stage between tanning and finishing |
| 6. Splitting and shaving | The hide is split and shaved to thickness | Sets thickness and opens the nap on suede |
| 7. Retanning, dyeing and fatliquoring | The leather is dyed, retanned and lubricated | Colors it and coats the fibers so they slide past each other |
| 8. Drying and finishing | Drying, staking and finishing steps follow | Sets the final feel and surface |
What "wet blue" means
Wet blue is the greyish-blue color chrome-tanned hide has when it comes out of the tanning bath and before dyeing. Undyed chrome-tanned leather is pale blue.
It is also a trade term. One factory profile says the factory buys hides in the wet-blue state from Argentina and Spain and dyes them in its own tannery to each buyer's color. A Leeds suede tannery says skins arrive in wet blue or wet white and are rehydrated, split, shaved, dyed and retanned there.
So the tannery that chrome-tans a hide and the plant that dyes and finishes it are not always the same.
How chrome tanning changes a jacket
Chrome tanning changes how leather behaves in ways a wearer can notice.
For a jacket this matters because the leather has to bend, stretch and drape. Chrome tanning produces a stretchable leather that is used for garments.
Leather Collection's jacket pages name the animal but do not state the tanning method. We cannot say which tannage a given Leather Collection jacket uses. For how a leather factory works, see Leather Collection's look inside the leather factory.
| Property | Chrome-tanned | Vegetable-tanned |
|---|---|---|
| Handle | More supple and pliable | Stiffer; used for luggage, furniture and belts |
| Thickness | Thinner leather | Thicker and stiffer |
| In water | Does not discolor or lose shape as drastically | Discolors; hardens and shrinks if soaked then dried |
| Shrinkage temperature | Over 100 °C (212 °F) | 70-85 °C (158-185 °F) when new |
| Tanning time | A day or two | Several weeks; as long as two months by one source |
Chrome vs vegetable: a short video
A leather supplier's presenter compares the two tannages. He puts chrome at about 80% of leather and a chrome tan at about two days, figures that differ slightly from the 85-90% and "a day or two" given above, and he describes chrome tans as the upholstery and garment leathers.
Is chrome tanning the only option?
No. Wikipedia's tanning article lists the alternatives. Vegetable tanning uses plant tannins, and wet white uses aldehydes or aluminum, zirconium, titanium or iron salts. See vegetable-tanned leather and what it means to tan leather.
Chromium(VI) is the concern people raise about chrome tanning. Chromium in leather covers what the EU limit is and what to ask a maker.
FAQ
What is chrome-tanned leather? Leather tanned with chromium(III) salts, usually chromium sulfate.
Why is it called wet blue? Because the hide is greyish blue and still wet when it comes out of the chrome bath.
How long does chrome tanning take? The chrome step takes less than a day by one source and a day or two by another. Vegetable tanning takes far longer.
What share of leather is chrome tanned? Sources differ: about 80%, 85-90% and as much as 90%.
LeatherGuru Editorial Team
LeatherGuru articles are researched from published sources, cited in the text, and reviewed before publication.