This is the first of two Bulletins that will discuss the removal of various types of stains from laundry items. General methods of stain removal will also be addressed. Most of these stains will be removed if appropriate laundry formulas are used; however, there will always be some stubborn stains that will require special treatment.
GENERAL METHODS OF STAIN REMOVAL
The following sequence of treatment steps should give you the best chance for stain removal:
- Wash with a concentrated built soap or detergent solution. Treat fugitive colors, silk, and wool fabrics with a concentrated soap solution (approximately 0.5 percent of neutral soap or detergent). If stain is not removed, go to step 2.
- Treat with organic solvents such as drycleaning solvent, volatile dry solvent, or acetone. Test fabrics to make sure the solvent will not affect the fabric or the color. Rinse well. If stain is not removed, go to step 3.
- Treat with a solution of sours such as oxalic acid, sodium and ammonium acid fluorides, and hydrofluoric acid. Rinse well. If stain is not removed, go to step 4.
- Treat with an oxidizing agent such as sodium hypochlorite (common laundry bleach). However, do not use sodium hypochlorite on wool, silk, nylon, or spandex, and test for colorfastness prior to use. Rinse well. If stain is not removed, go to step 5.
- Treat with warm solutions of reducing agents or strippers such as sodium hydrosulfite. Rinse well after using all of the above listed treatments.
(NOTE: If the stain is an obvious grease or oil-based stain, use Step 2 before Step 1.)
SPECIFIC STAIN CATEGORIES
▲ Albumin Stains
Albumin stains are caused by protein-based substances, such as blood, cream, ice cream, eggs, gelatin, mayonnaise, meat juices, milk, salad dressing, and vomit. Because such stains can be “set” by heat, it is important that the first wash used to remove these stains not exceed 100°F. The treatment should also be long enough to remove the protein matter prior to the application of hot suds and rinses. If a high temperature must be used, suds must be applied at the beginning of the wash cycle. Make sure the pH of the load is between 11.2 and 11.4 in order to avoid setting the stain.
If the stain is not completely removed after washing, a digester can be helpful since it attacks albuminous stains with enzymes, which make the stain soluble. Although digesters are extremely valuable for the removal of stubborn stains, they require a soaking period prior to washing. It is important that you follow the directions on the container precisely. Some of the enzymes in digesters are sensitive to heat and alkaline conditions. After using a digester, relaunder the article.
Some albuminous stains may contain grease. If the grease is not completely removed, spot with an organic solvent such as drycleaning solvent or a volatile dry solvent.
Blood stains are usually eliminated by the washing process. However, the use of a bleach may be necessary. Chlorine bleach is very useful in removing the hemoglobin stain but if the garment contains silk or wool or dyes that are not colorfast to chlorine bleach, you may consider substituting with hydrogen peroxide. In some cases, a brown stain may have developed from the iron in the blood. This can be removed by using an oxalic acid solution or a proprietary rust remover.
It is practically impossible to remove aged blood stains that are on sheets and towels from mortuaries. Although the discoloration may be lightened, they are seldom completely removed by the treatments listed above.
▲ Urine Stains
These stains generally appear as yellowish or brownish discolorations and usually will be removed during a regular washing process. If the stain remains, or an odor persists, rewash the article in a high alkalinity formula. If necessary, the use of a digester bath may be needed.
▲ Dye Stains
Dye stains, such those from direct contact with dyes, food dyes, or pencils, can be difficult to remove. Because it is often impossible to identify the type of dye, the bleach steps used in removal cannot be specific. While some dye stains can be removed solely by rewashing, others require the use of an oxidizing or reducing bleach. In some cases, removal of the dye stains may be nearly impossible.
The removal of dye stains on colored materials will depend upon the original color’s colorfastness. Whenever possible, use an unexposed portion of the garment for colorfastness testing. If it proves to be safe for the fabric, first use sodium hydrosulfite, a reducing bleach, then chlorine bleach, an oxidizing bleach. (Caution: Do not use on silk or wool. Use hydrogen peroxide on silk and wool.)
▲ Ring Around the Collar
The stain called “ring around the collar” is comprised of body oils and perspiration. With the resurgence of the French cuff, this staining is no longer specific to just the collar. This type of oily stain is not readily soluble in water.
For effective removal, hot water and high alkalinity are required. The laundry formula should contain three suds operations, ranging from 140°F to 160°F. The pH of the load during the sudsing operation should be around 11.0. This can be accomplished through the use of sodium orthosilicate and built soap. The use of this type of wash formula should eliminate a great amount of pre-scrubbing for collars and cuffs.
Mud stains are usually removed by washing. If residual brown stains remain, they are probably due to the presence of iron and can be removed with a warm or hot solution of oxalic acid or a proprietary rust remover. Rinse thoroughly after these treatments.
Concrete stains occur when a fabric comes into contact with wet cement. These stains are often permanent. In some cases, the lime can be removed by using a strong acetic acid; any residual stains may be removed with bleach. A two-percent solution of hydrochloric or nitric acid is recommended. (Caution: Use these acid solutions very carefully. Always pour acid into water— not water into acid— to avoid rapid chemical reactions. Do not use on protein fibers such as silk or wool. Use goggles and rubber gloves when handling acids.) It is extremely important that the fabric be thoroughly rinsed and neutralized with an ammonia solution after the use of such treatments.
▲ Iron (Rust)
To remove rust stains, use a reducing agent, such as oxalic acid, sodium or ammonium bifluoride, sodium trisulfate, or hydrofluoric acid. Every rust-removing treatment must be followed by a thorough rinsing. Oxalic acid does not rinse readily from fabric and can cause chemical damage. It is safer to use fluoride salt-based rust removers (ammonium or sodium fluoride) or hydrofluoric acid. Bifluorides and hydrofluoric acids are relatively safe for fabrics because they can be left in the fabric at lower concentrations without weakening the fabric. Fluoride compounds are hazardous and must be used carefully. Hydrofluoric acid is fatal to humans and must be used with extreme caution.
To remove rust using oxalic acid:
- Use a low water level in the washer at 150°F to 160°F.
- Add oxalic acid (8 to 16 ounces per 100 pounds of textiles that are being treated).
- Agitate for about 20 minutes.
- Follow with three to four rinses.
To remove rust using regular souring agents:
- Use two to three times the amount of regular sour at 160°F for 10 to 20 minutes.
- Follow with three rinses (hot, split, and cold).
- The treatment is useless unless the temperature is between 160°F and 170°F.