State pickle pH, salt, and whether you need wetting back or a small fatliquor in the pickle. They are different offers.
Acid and salt
Pickle floats are built to suppress acid swelling. They are also hostile to emulsions that were designed for a dye house at higher pH. A wetting agent for this stage has to stay useful in salt and acid, which is why the beam-house and early fatliquor notes matter more than a shampoo surfactant.
Esteem’s multipurpose emulsion is explicitly staged: pickle and tanning, rechrome, garments, upper and upholstery, at different percentages. Use the pickle line.
Wetting back dried stock
Crust or dried pickled stock that must be wet back is a different water demand from a pelt that never left the float. The same multipurpose grade notes excellent wetting-back properties. Name dried versus fresh on the request.
If wetting back is uneven, dye and fatliquor later will map that pattern. Do not wait until the dye house to discover it.
Reading a cut
A small pickle oil can improve the start of tannage and still leave the leather harsh. That is success at this stage, not a reason to dump the garment offer into the pickle.
Salt stains and acid pockets are process control. Surfactant will not fix a bad salt dose.
| Observation on the cut | Likely gap | Not the first lever |
|---|---|---|
| Chrome only at the grain | Pickle wetting or time | More dye fixer |
| Slippery grain, raw centre | Surface oil, poor penetration | Higher main fatliquor |
| Dried stock, slow rewet | Wetting-back package | A lime surfactant |
| Even blue, harsh later | Fatliquor, not pickle | Repeating the wetter |
Pickle sets the charge of the collagen
After deliming, the pelt is brought to low pH in salt so that acid does not swell it. That pH decides how chrome will bind later. If the acid does not penetrate, the surface is pickled and the centre is still near deliming pH. Chrome then strikes on the grain and leaves the centre under-tanned. A wetting agent in the pickle is there to make that penetration even.
Salt is doing two jobs: it suppresses acid swelling, and it changes surfactant solubility. A wetter that needs low electrolyte will separate as an oil slick on a strong pickle. The slick is not extra wetting. It is the product leaving the liquor.
Which surfactants survive the acid
Nonionics with enough solubility, sulfosuccinates, and some phosphate esters are the usual acid-side candidates. Soap-type anionics from the beamhouse are protonated and become fatty acids. They deposit in the pelt and later form chrome soaps. Carrying a lime-bath detergent into the pickle without checking acid stability is a common way to buy that defect.
Foam at pickle pH is again a separate complaint. Air in a pickle drum does not improve penetration. It reduces the liquor contact. Specify low foam if the drum is closed and the float is short.
How to see an uneven pickle
Cut the pelt after the pickle and check the pH through the cross-section with a suitable indicator or by a controlled method you already use. A surface at the target pH and a centre several tenths higher is a penetration failure. More acid on the surface will not fix the centre if the liquor is not entering.
State the acid, the salt concentration, the float, and the temperature. Also state whether the same wetter is expected to work in the chrome bath that follows. Acid stability and chrome-bath stability are related and not identical.
How to Specify with Esteem
- Give pickle pH, salt, and float length.
- Say if the pelt was dried or only delimed.
- Separate wetting back from lubrication.
- Keep chrome offer constant when you trial the wetter.
- Check penetration on a cut, not only surface slip.
The multipurpose fatliquor on fatliquors lists pickling and tanning at a low percentage, separate from garment offers.