Why old stains are harder

In detail

Every trade procedure this catalogue has read opens with some version of act quickly, and the reason is not urgency for its own sake. Four things happen to a deposit over time and each makes it harder. It PENETRATES, moving from the surface into the structure by capillary action, so a mark that could have been blotted becomes one that has to be extracted. It DRIES, which concentrates whatever was dissolved in it and brings the deposit into intimate contact with the substrate. It OXIDISES, and this is the one that changes the chemistry outright — many pigments and oils react with atmospheric oxygen into new, more strongly coloured and less soluble compounds, which is why an old oil mark yellows and why a stain nobody could see reappears brown months later. And in the case of sugars and some proteins it POLYMERISES or cross-links, becoming a solid film rather than a residue. The consequence is that the treatment which would have worked on day one may not simply be less effective later; it may be the wrong treatment for what is now there. The conservation guidance names brown oxidised stains as a category of their own, separate from greasy soiling and general grime.

Why

• Burnt-on food and carbon deposits is explained by Why old stains are harder
• Oil and grease on textile is explained by Why old stains are harder
• Coffee is explained by Why old stains are harder
• Fruit juice is explained by Why old stains are harder
• Rust is explained by Why old stains are harder
• Engine oil is explained by Why old stains are harder
• Bird droppings is explained by Why old stains are harder
• Coffee oil residue is explained by Why old stains are harder
• Soaking is explained by Why old stains are harder
• Lipase is explained by Why old stains are harder