A chrome-nappa percentage is not a vegetable-tannage formula. State veg, EI, or semi-chrome on the request.
Dispersion before addition
On semi-chrome and vegetable stock the problem is often fat that is already in the hide. A dispersing fatliquor is there to stabilize sulfated oils against electrolytes and to spread natural fat, not only to add softness. The Esteem dispersing grade says that in its application note.
Chrome nappa packages assume a different ionic bath. They can leave veg leather greasy in one area and empty in another.
Tannin and dye
Vegetable tannins react with cationic products and with some emulsions. The dispersing grade’s published stability to vegetable tannin is the reason to start there for combination work. It also claims a leveling effect on anionic dyes without excessive lightening, which matters when the retan is already dark.
If the dye lightens as soon as the oil goes in, you are looking at that dispersing effect, not at a dye-fixer failure. Change one of them.
Articles that are not chrome nappa
Phospholipid dispersions in the table give even softness and a warm silky feel and note limited stability to chrome and aluminium. That limitation is a reason to declare tannage, not a footnote.
Beam-house wetting and degreasing still decide how much natural fat reaches this step.
| Tannage | Selection emphasis | Risk |
|---|---|---|
| Vegetable | Natural-fat dispersion | Drawn grain |
| EI / combination | Tannin-stable dispersant | Patchy oil |
| Semi-chrome | Dispersing plus chrome awareness | Chrome soap |
| Chrome nappa | A different package | Copying it onto veg |
The fibre is already full
Vegetable tannins are polyphenols. They hydrogen-bond and bind across collagen, so the leather is full, acidic, and less willing to take a large anionic oil offer than a chrome leather of the same thickness. The fatliquor’s job is often to disperse residual natural fat and to give a controlled lubrication, not to soften the leather the way a garment chrome fatliquor does.
If the emulsion breaks on the acid grain, oil deposits as a surface film. The centre stays dry and the grain looks dark and greasy. A weakly anionic or nonionic dispersing grade is used because it is less likely to shock out on that surface. The grade still has to be chosen for vegetable tannage, not copied from a chrome main-fatliquor line.
Natural fat is part of the formula
Hides and skins carry glycerides and waxes. In chrome leather a lot of that fat is removed or combined earlier. In vegetable leather more of it remains, and it becomes the bloom that customers call spew. A dispersing fatliquor is there to distribute that fat through the structure so it does not travel out later.
Adding a heavy sulfited oil on top of undispersed natural fat increases the mobile fraction. The leather may feel softer in the drum and then bloom in storage. Degreasing, or a dispersing offer before the main oil, belongs in the process if spew is the complaint.
Acidity and exhaustion
Vegetable liquors sit at low pH. An emulsion stabilised for a dye-house pH near 4 to 5 can coarsen in a stronger vegetable bath. Coarse droplets do not penetrate. They filter out on the grain. Temperature and float length change the same result: a short hot float exhausts a fine emulsion; a long cool float lets it cream.
Specify the tannage (mimosa, quebracho, or a blend), the pH at the fatliquor addition, and whether the defect is empty centre, dark grain, or bloom after storage. Those three defects are three different oil decisions.
How to Specify with Esteem
- State veg, EI, semi-chrome, or combination.
- Describe drawn grain, chrome soap, or greasy patches if you see them.
- Use a dispersing grade stable to vegetable tannin for the combination work.
- Do not copy a chrome garment offer.
- Check grain after drying and toggling, not only in the drum.
The weakly anionic dispersing fatliquor on fatliquors is described for semi-chrome and combination leathers and for stability to vegetable tannin.