If the article is white, pastel, or aniline, say so in the first line. A garment fish-oil offer is a different product.
What the table actually promises
The lightfast synthetic is a brown clear liquid that forms a micro-emulsion, penetrates the cross-section, and is called out for white, pastel, and aniline. It is also described as compatible with fish oil and vegetable oil. Compatibility is not permission to add those oils to a white formula.
The nonionic paste is called out for white and pastel because of lightfastness and for elegant handle. The cationic paste is called out for high lightfastness and electrolyte stability. Pick from those sentences.
Heat as well as light
Furniture and shoe nappa see heat as well as light. The synthetic-oil specialty softener is described for furniture, garments, and shoe nappa with lightfastness and heat resistance. That is the sentence for upholstery whites, not the fluffiest garment oil.
Aniline leather shows every discoloration. Finish cannot hide it. Align the fatliquor with the finishing chemicals before the shade is approved.
Offers are not interchangeable
Offers on the lightfast synthetic include white goat and sheep at a higher shaved-weight percentage than cow nappa. Copying the cow number onto a sheep skin under-softens it, and copying the sheep number onto bovine can greasy the grain.
Record the lamp and the time. A pass at four hours is not a pass at the customer’s method.
| Article | Start from the note that says | Avoid as the main oil |
|---|---|---|
| White goat or sheep | Lightfast synthetic, higher offer | Unstated fish oil |
| Pastel suede | Nonionic lightfast handle | A dark sulfited blend |
| Aniline grain | Lightfast synthetic penetration | Surface grease |
| Furniture nappa | Heat and light resistant softener | A garment fluff oil only |
What lightfast means chemically
Lightfastness here means the fatliquor does not develop colour under the light and heat the leather will see. Synthetic esters and selected nonionic or cationic products are used because their chains are less prone to that oxidation than drying oils and fish oils. The table calls this out on specific grades. It is not a property of every synthetic oil, and it is not created by calling an oil synthetic on the purchase order.
Compatibility with fish oil, which the lightfast synthetic notes mention, means the emulsions can be mixed. It does not mean the mixture stays lightfast. The fish-oil double bonds are still in the leather.
White, pastel, and aniline fail differently
A white shows yellowing as a shade change against a standard. A pastel shows it as a dirty cast. Aniline grain shows it immediately because there is no pigment finish to hide the crust. Furniture nappa adds heat: a lamp test without a heat condition misses the failure the upholstery specification is written around.
The specialty softener described for furniture, garments, and shoe nappa with heat resistance is the sentence for that upholstery case. A high-offer sheep or goat garment oil, even a lightfast one, is a different offer and a different hand. Copying percentages between those articles is how whites become greasy or goat skins stay empty.
How to isolate the cause
Change one of dye, fatliquor, or fixing agent per trial. Dry the leather the way production dries it, then expose it. A wet bath that looks pale can oxidise in the toggle or the vacuum dryer. Record the lamp, the hours, and the temperature, because a four-hour pass is a different specification from the customer’s method.
If a blend is required for hand, add the dark oil in a known small step and retest. Stop at the last step that still passes. That step is the specification. A verbal “a touch of fish oil” is not.
How to Specify with Esteem
- State white, pastel, or aniline.
- Name the lightfastness method you already use.
- Avoid fish-oil and dark sulfited blends unless they are proven on that shade.
- Keep dye and fatliquor changes separate.
- Check yellowing after drying, not only in the wet bath.
The lightfast synthetic, the nonionic handle modifier, and the cationic high-lightfastness grade are all on fatliquors.