6 Leather Decisions You Can't Undo After First Run
The header guide covers what to decide before your first prototype. This is the sequel: what's already frozen the moment your first production run ships, and what it costs to change any of it on the second one.
A guide by TL San Martín, a tannery of origin in Elda (Alicante, Spain) since 1995, LWG Gold certified under the Leather Manufacturer standard.
Colour, thickness, batch (drum load), tannage type, finish, and lining all lock in at first production — not at prototype stage. Changing any of them afterward means a new lab dip, a new minimum order, or in some cases a different tariff classification. Knowing which of the six you're actually free to revisit before you commit is what separates a founder's second order from their first.
Our guide on the leather decisions nobody explains covers what a founder has to decide before the first prototype is cut. This is what comes after: the moment your first production run actually ships, six of those decisions stop being decisions. They're now specifications, written into your pattern, your costing, and — in a couple of cases — your customs paperwork. Changing any of them for run two isn't a tweak. It's closer to a re-launch of that colourway.
Here's what locks, and what it actually costs to reopen each one.
What leather decisions freeze after your first production run?
| # | Decision | What "locked" means | Cost to change on run two |
|---|---|---|---|
| 1 | Colour (approved shade) | Your PP sample and lab dip become the reference every future dye lot is measured against | A new lab dip, a new approval cycle, and — if it's a bespoke shade — a new colour minimum (see below) |
| 2 | Thickness / substance | Your pattern, stitching, and last are built around one gauge | Re-costing the pattern, possible re-tooling of dies, and a new thickness spec on the tannery's cutting order |
| 3 | Batch / drum load (the "partida") | Your first run's shade and hand come from one specific drum | A different drum is, by definition, a different partida — some variation is normal, not a defect |
| 4 | Tannage type (chrome vs chrome-free) | Chemistry, hand, and often the finish process are built around the tannage | Switching tannage is closer to sourcing a new material than adjusting an order |
| 5 | Finish (pigmented, semi-aniline, aniline) | The finish determines fold behaviour, scuff resistance, and how the grain reads | A different finish on the same crust can require a new lab dip and a new hand approval |
| 6 | Lining spec | Lining thickness and tannage are matched to the upper for comfort and durability | Changing lining after launch means re-testing the pairing, not just re-ordering leather |
Why does the colour lock in so hard once you've shipped?
Because your approved PP sample — not the swatch, not the lab dip — becomes the legal reference for every dye lot the tannery mixes after that. If your first run used a bespoke shade, you've also set your colour minimum: a tannery doesn't tan a drum for one small reorder, so a custom colour's real minimum is the size of a drum load, not the size of your order. Our guide on crust leather and the real colour minimum explains why dyeing from crust already in stock is the one lever that can lower that minimum on a reorder — but only if the crust itself was part of the original decision.
Why can't I just ask for a slightly thicker leather on run two?
You can ask — but it isn't "slightly." Footwear leather is measured to ISO 2589 and specced with a tolerance, commonly around ±0.1 mm for uppers, and your factory's pattern and stitching allowances are built around that number. Move the substance and you're not adjusting a spec, you're re-costing the pattern: seam allowances, skiving, and in some constructions the last itself all assume one gauge. See leather thickness for shoe uppers for how substance is selected by construction in the first place — before it locks.
Does the drum load actually matter, or is that just tannery jargon?
It matters more than most founders expect. Two hides tanned in different drums — even to the same formula — will show small, normal variation in shade and hand. That's not a defect; it's the nature of a natural material processed in batches. What it means practically: your first production run's "reference" pair of shoes came from one partida, and a reorder from a new drum should be expected to sit close, not identical. If your factory or your customers need identical, that has to be written into the spec — and priced — from day one, not assumed for free.
What does switching tannage actually involve?
More than a supplier swap. Chrome and chrome-free (vegetable, or other chrome-free systems) tanning produce leather with different hand, different behaviour under heat and folding, and often a different compatible finish. If chrome-free compliance — REACH Annex XVII entry 47, tested to EN ISO 17075, with the 3 mg/kg chromium VI limit — becomes a requirement after your first run has already shipped in chrome-tanned leather, you're not amending an order, you're sourcing a second material and validating it against your existing pattern from scratch. Our guide on chrome-free leather for shoe brands covers when that switch is worth the cost and when it isn't.
Is the finish really locked, or can I change pigmented to aniline later?
Technically yes, practically rarely without consequence. A pigmented finish adds a protective coat that changes how light hits the grain, how the leather folds at the toe, and how it takes wear — none of which are true of an open aniline finish on the same crust. Change the finish and your factory's fold-radius allowances, your durability testing, and possibly your lightfastness rating (pigmented finishes generally hold colour better under light exposure than aniline) all need re-checking. It's a new material decision wearing the old crust's name.
Founders comparing tanneries before locking any of these six in are exactly who the TL San Martín Business Board was built for — post in Materials or RFQ · Production and get quoted before the decision, not after it's already frozen in your first production run.
Frequently asked questions
If I only change the lining, does the rest of the spec stay locked?
Mostly, but not entirely — lining thickness and tannage are usually matched to the upper for comfort and moisture handling, so a lining change on its own should still be re-validated against the upper spec rather than swapped in isolation.
Can I renegotiate the colour minimum after the first run if I switch to a stock shade?
Yes — a stock shade drawn from leather already dyed and held by the tannery has effectively no practical minimum, unlike a bespoke colour that requires its own drum. This is the fastest of the six to "unlock."
Does a different drum load count as a defect I can reject?
Normal batch-to-batch variation isn't a defect on its own — it's inherent to a natural material processed in drums. What matters is whether your agreed tolerance, set at the PP sample stage, was met. If it wasn't, that's a claim; if it was, that's leather doing what leather does.
Which of the six is cheapest to change on a second order?
Colour, if you move to a stock shade instead of a bespoke one. Thickness, tannage, and finish all touch the pattern or the chemistry and are the most expensive to reopen once a production run has shipped.
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.