What to Expect From Your Tannery at Each Sample Stage
A footwear brand's development calendar has four material checkpoints, and each one is cut from a different piece of leather. Knowing what each stage can and can't confirm avoids surprises when bulk arrives.
A guide by TL San Martín, a tannery of origin in Elda (Alicante, Spain) since 1995, LWG Gold certified under the Leather Manufacturer standard.
A tannery works through four distinct samples, not one: a swatch, a lab dip, a pre-production (PP) sample, and the bulk delivery. Each comes from different material — a stock skin, then a test dye lot, then the actual planned batch — so approving one doesn't approve the next. The PP sample is the one most often skipped, and it's the closest thing to a preview of what the bulk will actually look like.
A shoe factory's development calendar has names for every stage — fit sample, proto, PP sample, TOP, bulk. Most footwear founders learn those names from the factory. What's less visible, because the factory doesn't usually spell it out, is that the leather changes at every one of those stages too — cut from a different piece of hide each time, with a different level of certainty attached to it.
Treat all four as "a sample" and it's easy to approve something once and then be surprised twice: once when the shoe factory says the lining doesn't quite match the upper, and once when the finished shoes arrive a shade off from what was first signed off.
What are the four leather samples in a development calendar?
| Stage | What it's cut from | What it actually confirms | What it does NOT confirm |
|---|---|---|---|
| Swatch / hand sample | A single skin already in the tannery's stock, close to the target | Hand, grain, general colour family | Exact shade, thickness spec, or availability at your volume |
| Lab dip | A small test dye lot, mixed toward your reference | The formula gets close to your colour, on that skin | Whether the bulk dye lot will land in the same range |
| PP sample (pre-production) | Leather cut from the crust and dye lot planned for the bulk order | Shade, thickness, and finish close to how it will actually ship | Nothing perfectly — natural material still carries some variation |
| Bulk delivery | The full order, tanned and dyed in one production run | Consistency across hides within that one run | Consistency with a future reorder (see the note on repeat orders below) |
The swatch and the lab dip both happen before a drum is committed to an order. The PP sample happens after — it's the closest of the four to being cut from the same batch the shoes will be made from, though as a natural material it's still not a pixel-perfect guarantee. Our guide on colour approval covers how the lab dip stage works in detail; this piece is about the calendar around it.
Why can a swatch look right and the bulk still come out a little different?
Leather is a natural substrate. Two skins tanned in the same drum still vary hide to hide, and a single hide varies zone to zone — the butt takes dye differently than the belly or the neck. A synthetic material dyed from a formula doesn't have this problem; leather does, and it's not a defect, it's the nature of the material.
That's the gap between approving a swatch — one skin, usually a good-looking example — and approving a PP sample cut from the actual planned batch. If a bulk shipment has already come in off-shade or off-thickness from what was signed, that's a different, more specific problem: see why bulk leather doesn't match the sample for how to diagnose it. This guide is about narrowing that gap before the bulk order is ever cut.
What's worth confirming on a PP sample, together with your tannery?
A useful PP sample isn't just a bigger swatch. It's worth agreeing with your tannery, upfront, how you'll both check a few things — most tanneries are glad to align on this, since it saves rework on their side too:
- Shade, under more than one light. Daylight (D65), shop lighting, and incandescent read colour differently — a piece that matches under one can look different under another. It's reasonable to ask whether the PP piece can be viewed under a couple of these together.
- Thickness, as a measured number, not an estimate. Leather thickness is measured to ISO 2589 and quoted with a tolerance — commonly around ±0.1 mm for footwear uppers. Confirming this on the PP sample, rather than assuming it, avoids a mismatch discovered at the pattern-cutting stage.
- Finish and hand together. A pigmented finish changes how leather folds and how the grain reads compared with an aniline or semi-aniline finish on the same crust. If a pattern is built around a specific fold radius, it's worth confirming that on the PP piece rather than the earlier swatch.
For lightfastness — whether a colour will hold up under a shop window or daily wear — the general industry reference point is EN ISO 105-B02, tested against the Blue Wool scale, with commonly cited minimums around grade 3 for aniline or nubuck finishes, grade 4 for semi-aniline, and grade 5 for pigmented leathers. Not every tannery runs this test on every order by default — it's worth asking early whether it's included, since testing takes time and, on some orders, a small additional cost.
Who checks what on the PP sample?
Roughly: your factory checks that the PP sample cuts and constructs the way the pattern expects. You and your tannery, together, confirm the material is close enough to what was ordered — shade, thickness, finish, hand — and agree in writing which reference governs if the eventual bulk delivery and the PP sample end up slightly apart: the PP sample itself, or the original lab dip. Our guide on your first leather order covers this "two references" idea and why it helps to settle it before the bulk order ships, not after.
Does the calendar reset on a reorder?
Partially. A reorder in the same colour and spec usually skips the swatch stage — the hand and grain family are already known — but a fresh PP sample is still worth requesting. A new dye lot, even mixed to the same formula, is a new drum, and the same zone-to-zone and hide-to-hide variation applies. Treating a reorder as identical to the last one without a fresh PP sample is one of the more common ways two production runs of the same shoe end up visibly different on shelf — not because anything went wrong, but because nobody re-checked.
Conversations like these are exactly what the TL San Martín Business Board exists to support — post a Materials or RFQ · Production listing and compare how different tanneries handle sampling before committing to a first order.
Frequently asked questions
Is a PP sample always necessary if the swatch already looked right?
It's the more reliable check. The swatch is one hand-picked skin from stock; the PP sample is cut from the actual dye lot and crust the bulk order will use. They can legitimately differ a little, and the PP sample is the closer preview of the finished shoes.
How big should a PP sample be?
Large enough to view under a couple of different light sources, and large enough for a factory to test-fold or test-stitch a small piece if construction depends on hand. Worth agreeing the size with your tannery upfront rather than assuming.
Does every tannery offer a PP sample as standard?
Not always, and it's reasonable for it to come with a small charge or added lead time — it's a real cut from planned production material, not a leftover offcut. Asking early, as part of the order conversation, avoids a surprise later.
Does a PP sample apply to lining leather too, or only the upper?
Both are worth including. Lining leather has its own thickness and, on some brands' sheets, chrome-free specs, and it goes through the same swatch-to-bulk gap as the upper. If a shoe pairs a specific lining with a specific upper, it helps to request PP samples of both together.
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.