Leather supplier audit: what to check on a tannery visit
A certificate tells you what an auditor saw on one day. A two-hour visit tells you whether the leather you will pay for comes out of that building. Here is the order in which to look.
A guide by TL San Martín, a tannery of origin in Elda (Alicante, Spain) since 1995, LWG Gold certified under the Leather Manufacturer standard.
Before a first leather order, a tannery visit should verify three things: that the address on the LWG certificate is the site you are standing in, that the machines on the floor match the certificate's audit category, and that one batch can be traced from drum to label. Leave with five documents in writing; a supplier who cannot give them has told you something.
Why visit at all if the tannery is certified?
Because a certificate and a visit answer different questions. An LWG certificate says that one site, at one address, passed an environmental audit against a named standard within the last 24 months. It does not say that the leather in your quote is made there, in the article you approved, from the process you assume.
Most buyers skip the visit for a first order of a few hundred square metres. That is reasonable. But if the programme will repeat — a footwear brand re-ordering every season, a group re-lining its shoes every year — two hours on site cost less than one wrong batch. Do the paperwork first with the 12 questions to ask a leather supplier; visit to confirm the answers.
Three terms, translated once. Crust is leather that has been tanned and dried but not yet finished. Finishing is the surface work — colour, top-coat, embossing, milling. Batch (or lot) is one production run from the same drums, with one colour result.
Does the site match the certificate?
Start at the gate, not in the showroom.
- Address. Open the certificate on the LWG public directory on your phone. The audited address must be the one you are standing at. A second warehouse or a finishing unit across town is not covered unless it has its own audit.
- Standard. LWG runs four standards: Leather Manufacturer, Commissioning Manufacturer, Trader and Subcontractor. Only the first two award medals; a Trader reaches at most "Approved". If you are told "we are LWG" at a site that holds a Trader certificate, you are at a merchant, which is legitimate but changes who you should be auditing. The difference is explained in tannery or distributor.
- Audit category. This is the check almost nobody makes, and it takes one minute.
| LWG category | Process covered | What you should see on the floor |
|---|---|---|
| A | Raw hide/skin to tanned | Salted hides, beamhouse, tanning drums |
| B | Raw to crust | As A, plus retanning, dyeing and drying |
| C | Raw to finished | The whole chain, beamhouse to spray line |
| D | Tanned to finished | Tanned stock arriving, retanning, drying, finishing |
| E | Crust to finished | Crust arriving, finishing lines, milling drums, measuring |
| F | Tanned to crust | Retanning, dyeing and drying, no finishing line |
| G | Raw to pickled / pre-tanned | Beamhouse and pickling only |
Source: LWG Leather Manufacturer Standard, audit scope. A category is not a ranking: a category E site finishing leather to a tight colour standard is as legitimate as a category C site. What matters is coherence. If the certificate says E and you are shown raw hides, ask where they go. If it says C and there is no beamhouse, ask where the certificate was earned.
How to read the rest of the certificate — medal, validity, traceability percentage — is in how to read an LWG certificate. One reminder: traceability is scored separately, as a percentage, and can be 0 % on a certificate in good standing. A medal is not proof of hide origin.
Can one batch be followed from drum to label?
Ask to follow one real batch, preferably one in production that day.
- Drum or recipe card. Every batch should carry a recipe reference: article, colour, date, drum. If the answer is "the operator knows", repeatability depends on one person.
- Rack or pallet label. The same batch number should appear on the stock, not only in a system screen.
- Measuring. Leather is sold by area. Ask to see the measuring machine and when it was last calibrated; ask whether your invoice is issued from its printout. A few percent of area is a few percent of your price.
- Retained samples. A good tannery keeps a physical cut of each shipped batch. That cut is what settles a colour dispute. How to sign off colour before production is in leather lab dip approval.
- Grading. Watch a sorter at the selection table for five minutes. Then read what leather grades on an invoice commit to and ask which grade your quote assumes.
What does the warehouse tell you?
The stock room answers the question every sales deck blurs: is what you were quoted produced, on a shelf, or reserved in your name? Ask to see the rack where your article would sit. The three meanings of "in stock" and what each costs you are in catalogue, shelf or reserved batch.
Also look at what sits on the floor as second choice. Every tannery has it; how it is sorted and sold tells you how the first choice is protected. What is normal on a hide and what is a defect is covered in leather defect or normal.
Which five documents should you leave with?
| # | Document | Why it matters |
|---|---|---|
| 1 | Certificate URN and audited address, in writing | Ties the medal to the site you visited |
| 2 | Technical data sheet of your article | Thickness range, tannage, finish, tolerances |
| 3 | Chemical test report, per batch | Chromium VI below 3 mg/kg under REACH Annex XVII entry 47, tested to EN ISO 17075 |
| 4 | Written production address for your order | Makes "who makes it" a contract term, not a conversation |
| 5 | Batch reservation or lead-time confirmation | Separates a quote from a commitment |
If any of these arrives as "we'll send it later", note the date you asked. A supplier who delivers all five within a week of the visit has passed the part of the audit that matters most: saying in writing what they showed you.
At TL San Martín the visit is part of the process for brands building a repeat programme; the plant and the team are introduced in behind TL San Martín. We are LWG Gold under the Leather Manufacturer standard — the only standard in which the Gold medal exists; a Trader reaches at most "Approved". If you are still choosing materials before any visit, start with leather for shoes: what to buy first.
Post your RFQ on the Business Board
Preparing a first order and want tanneries to answer with documents, not adjectives? Post it under RFQ · Production on the open Business Board: article, thickness, quantity, and the five documents you expect. If you need a factory to make the product and not only the leather, the category is Partners & factories. Or request physical samples with the technical sheet of the article.
Frequently asked questions
How long should a tannery visit take?
Two hours is enough for a first visit: thirty minutes on documents at the gate, one hour following a batch through the plant, thirty minutes in the warehouse and on the five documents. A longer visit adds colour work, not verification.
Is a video call an acceptable substitute?
For the documents, yes. For the audit category check and the batch walk, only if the camera moves freely and you choose what it shows. A pre-recorded tour verifies nothing.
What if the certificate address and the plant address differ?
Ask which activities happen at each site and whether both are audited. A finishing unit at a separate address without its own certificate is common and not illegal, but the medal on the quote does not cover it.
Should I visit before or after the first sample?
After. Approve the sample first, then visit with that article in mind, so you can follow the same article on the floor instead of a showcase one.
TL San Martín tans and finishes leather in Elda, Alicante, since 1995: LWG Gold under the Leather Manufacturer standard — the only standard under which a Gold medal exists at all; a Trader tops out at “Approved”. Request samples before you specify anything.