Pigment retention

In detail

A soil sits on or in a material; a stain is a colour bound to it. The distinction decides what success looks like. Where a pigment is merely deposited, lifting the carrier lifts the colour with it. Where the colouring molecule has bound to the fibre or penetrated the substrate — by the same mechanisms a dye uses, because many stains are dyes — the substance can be entirely removed and the colour remain. That is why the conservation guidance says microorganism growth PERMANENTLY stains a textile, leaving a darkened area that only radical treatment would diminish; the organism is long gone. It is why the stone trade separates etching from staining and treats the first as a re-polishing problem. And it is why the honest end of many procedures is not a solvent but a decision. What removes bound colour is not cleaning at all but bleaching — an oxidiser that destroys the chromophore rather than dissolving it — which is a different operation with a different risk, since it cannot distinguish the stain's colour from the material's own. Sunlight does the same job more slowly and with the same limitation.

Why

• Red wine is explained by Pigment retention
• Coffee is explained by Pigment retention
• Tea is explained by Pigment retention
• Tomato stain is explained by Pigment retention
• Mustard stain is explained by Pigment retention
• Fruit juice is explained by Pigment retention
• Ink is explained by Pigment retention
• Permanent marker is explained by Pigment retention
• Grass is explained by Pigment retention