by Aziz Ullah, Ph.D., MBA

It’s a fact that aging edible oils — especially certain varieties — will create yellow stains very difficult to remove from textiles.

Several possible chemical structures have been suggested that contribute to this yellowing color, including diketones and metal salts.

Oils that are unsaturated are particularly prone to yellowing.

Edible oils will oxidize on exposure to air. This is a natural process.

The studies show…

Studies have revealed several factors that accelerate the food oil auto oxidation:

1. One is the fatty acid composition of oil. Unsaturated fatty acids like oleic and linoleic acids oxidize rapidly.

2. A second factor in favor of oil oxidation is the increased surface area inherently present with oils on textiles.

3. Increasing oxygen concentration is another way of promoting oxidation, as is;

4. Exposure to ultraviolet light and other ionization radiation.

5. Metals are major pro-oxidants. Metals are present in oil, earth soil on the fabric and dye mordants.
 
A suitable stain removal system must remove stains without causing harm to the color and structure of the textile.

In one study, three methods were examined on removing aged oily stains. The cleaning methods examined were:

Dry-cleaning solvent with ultra-sound

Spotting with solvent and vacuuming

Pre-spotting simulation of hand washing

When oil binds particulate matter to the fiber, the cleaning process consists of two parts: Breaking up the oil by detergency in wet cleaning or solvency in dry-cleaning and dislodging the particulate matter with mechanical action.

Rubbing the fabric by hand or machine can supply the mechanical action.

In the study, olive oil was aged by oxidation. The fabrics were cleaned by all three methods and measured by the three indexes: Stain Removal Index (SRI), Percent Soil Removal Index (PRI), and the AATCC Gray Scale.

It was found in the analyses of pre-spotter cleaning that dyed fabrics showed higher cleaning ratings than did the non-spotted fabrics.

When the pre-spotter cleaning system was examined by PSR, both the textile and dye were found to be important factors.

Wool and dyed textiles showed the best cleaning in the pre-spotter cleaning system.

Evaluation of the cleaning process by Percent Soil Removal showed that the textile type and the cleaning systems had a significant effect in cleaning when the systems were exposed to ultrasound and vacuum.

Cotton was cleaned better than wool and the vacuum system was the best cleaning system. These results compare favorably with the Stain Removal Index results.

Final results

All stain removal systems used were successful in removing highly oxidized oily stains from cotton and wool fabrics.

Overall, the vacuum system was the best cleaning system.
 
However, the pre-spotter system was superior for cleaning most fabrics but inferior for cleaning cotton.

Several interaction effects were encountered between the dye in the fabric and other factors in stain removal. Therefore, the presence of dyes should be given special consideration in cleaning.

Aziz Ullah, Ph.D., MBA, is president of Fabpro Manufacturing, and is a leading formulator of top-quality carpet and upholstery cleaning products. He is a member of the American Chemical Society, senior member of the American Association of Textile Chemists and Colorists, and member of The Textile Institute (UK). He can be reached at www.fabpro.com.