31.14 How do I remove stains and deposits?
Description
This article is from the Chemistry FAQ, by Bruce Hamilton B.Hamilton@irl.cri.nz with numerous contributions by others.
31.14 How do I remove stains and deposits?
- Test any planned treatment on an unimportant part of the material first,
(spots and holes aren't currently fashionable ).
- Chemicals for removing stains are often toxic and corrosive, handle with
care, and follow any provided safety instructions.
- Often stains are a diverse mix of chemicals, and the best solution is
to solubilise as much as possible, remove insoluble material through
washing, and then carefully bleach. Chemists should not assume they can
perform this process better than housewives.
- Some stains are more easily removed by physical means - such as using
abrasives ( household cleaning pastes, steel wool, metal polishes, etc ),
or freezing solid and scraping ( chewing gum ).
- The fresher the stain, the easier to remove. Avoid using hot water or soap
on unknown stains, and use solvents (eg glycerine) to help keep the stain
fresh. In cases when the stain is known to be water-soluble (eg bird
droppings ), it is often preferable to allow the stain to dry and carefully
scrape most away, before additional treatment.
- When using solvents, apply around the outer edge of the stain and work
towards the centre to prevent a stain ring forming.
- Many stains result from pigments, and they are seldom soluble, so once the
other components are removed, use physical agitation to remove the
insoluble material.
- Sometimes a dried stain can be "freshened" by using more of the stain
before treating - but use this approach very cautiously.
There are books on stain removal [25,26,27], and many of the common recipes
are also often found in some home-care and cookery books. Home-care magazines
also have question and answer sections that frequently include advice on
how to remove specific stains. Very few chemical books cover chemical
cleaning and stain removal, and smart chemists avoid offering to remove
stains :-). Common stains are usually attacked with the household chemical
arsenal that may include:-
* Absorbents - Cornflour, French chalk, fuller's earth, starch, talcum powder.
* Acids - Inorganic = hydrochloric ( galvanising remover, concrete cleaner ).
- Organic = acetic ( white vinegar ), citric ( lemon juice ),
tartaric ( cream of tartar )
* Alkalis - Sodium hydroxide ( drain cleaner ), ammonia solution,
* Bleaches - Sodium hypochlorite solution ( household bleach ), calcium
hypochlorite ( bleaching powder ), hydrogen peroxide
* Drycleaning Fluids - 1,1,1-trichloroethane, perchloroethylene.
* Enzymes - Pepsin
* Petroleum Fractions - mineral turpentine, kerosine, gasoline, white spirits.
* Sodium carbonate ( washing soda ), sodium bicarbonate ( baking soda ),
sodium tetraborate ( borax ).
* Solvents - Acetone ( nail polish remover ), amyl acetate, methanol, ethanol
( methylated spirits ), glycerine, toluene, xylenes, iso propyl
alcohol.
* Terpenes - Eucalyptus oil, citrus oil, camphor
Specific Stain Strategies.
Ballpoint - methylated spirits, fullers earth, glycerine.
Blood - cold salty water, cornflour paste, or dilute bleach.
Copper deposits on sink or bathtub - ammonia (1 hr) then detergent.
Chewing Gum - freeze, or sponge with eucalyptus oil.
Chocolate - methylated spirits, or soak in 5% borax solution
Lipstick - glycerine, eucalyptus oil, dry-cleaning fluids.
Rust - oxalic acid, citric acid, tartaric acid
Tar - toluene, xylenes, eucalyptus oil.
Tea or Coffee - glycerine, warm borax solution
Wine - glycerine, borax solution, lemon juice
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