Tell Esteem the finish is aniline, semi-aniline, or pigmented. The fatliquor offer that suits corrected grain can block an aniline coat.
Oil belongs inside the leather
Cross-section softness and a dry, finishable grain can coexist. Overfatliquoring and a heavy top oil push oil outward. Aniline binders then sit on a film of oil and fail flex or tape tests.
Corrected and pigmented finishes tolerate more surface character than aniline, which is why the same crust can be finished one way and rejected the other. Write the finish route on the fatliquor brief.
Spew and storage
Spew that appears after days in a warm warehouse is a different complaint from wet-drum slip. It is often free fatty matter or a salt. A customer who only rubs the crust in the dye house will miss it.
Ask for exhaustion and, if you already see spew, say what it looks like. Esteem cannot guess a warehouse condition from a softness word.
Finish route
Top fatliquors are for handle after the main oil has exhausted. They are the first thing to reduce when adhesion fails, not the first thing to increase.
Dye fixing and finish adhesion are different tests. A well-fixed dye can still sit under a lifted film.
| Finish | Fatliquor constraint | Typical failure |
|---|---|---|
| Aniline | Low surface oil, lightfast | Lift, cloudiness |
| Semi-aniline | Controlled grain oil | Patchy cover |
| Pigmented / corrected | More tolerance, still no spew | Poor plate or adhesion |
| Naked crust | Handle only | Not a finish test |
Adhesion needs a surface the finish can wet
A finish film sticks when it wets the grain and then hardens without a weak boundary layer. Free oil, wax, and some emulsifiers are exactly that layer. They were useful in the drum because they lubricated the fibre. On the surface after drying they are a contaminant. The amount that is too much is the amount that has not been bound or exhausted into the cross-section.
Aniline and semi-aniline finishes are thin by design. They cannot hide a grain that beads water or that peels at the first flex. Corrected grain with a heavy base coat can tolerate a slightly richer surface and still look acceptable, which is why an oil approved on corrected leather can fail the same crust when the finish is changed to aniline.
Where the surface oil comes from
A coarse emulsion, a cationic top used for handle, a fish-oil fraction that migrates, or a main offer that was simply high, all leave material at the grain. So does poor wetting-back of a dry crust before finishing: the finish sits on a hydrophobic surface. These are different mechanisms and they need different corrections. Raising the finish binder does not fix a migrating oil.
Spew that appears after the finish is applied is oil that was still free to move. It can lift the film weeks later. A peel test on day one will miss it. The brief should say whether the failure is immediate poor wetting, immediate peel, or a later bloom under the film.
What to change first
Hold the finish constant and reduce or restage the fatliquor until the grain wets and the peel passes. Then put handle back with a grade meant to exhaust, not with more surface oil. A lightfast, penetrating synthetic is the usual direction for aniline crusts that must stay pale and bondable.
State the finish type, the peel or flex method, and the fatliquor stage that is allowed to move. A sample request that only says “aniline adhesion” will otherwise be answered with a softer oil, which is the wrong direction.
How to Specify with Esteem
- State aniline, semi-aniline, or pigmented.
- Note any spew or greasy feel before finishing.
- Keep a panel with a lower main-fatliquor offer.
- Do not raise top oil to fix a dry break if adhesion already fails.
- Test adhesion and flex after finish, not only crust hand.
Pair finishing chemicals with the fatliquor table. The leather finishing article covers coating and handle from the finish side.