Bleach Damage Issues
Oxidising bleaches include sodium hypochlorite (domestic bleach) and hydrogen peroxide (which can either be added as a liquid to the wash or it can be generated from the wash powder – look for sodium perborate and sodium percarbonate on the detergent contents). Oxidising bleaches react with vegetable dyes to change them from coloured to colourless. They also react with the cellulose in cotton and linen, rupturing the polymer chain and causing accelerated weakening so that the linen tears and frays very easily and can go into holes.
- You can minimise this problem with sodium hypochlorite by using it at the correct concentration and by restricting the dosage (6ml of concentrated bleach per kilogram of work). Sodium hypochlorite bleaching must be carried out below 50°C, because above this stain removal is minimal and accelerate fabric degradation occurs.
- Hydrogen peroxide is usually designed to work at around 65°C and there is no risk of excessive linen damage provided the concentration and stage times are correct. Hydrogen peroxide works much more slowly at lower temperatures. As a general rule, overnight soaking in very weak sodium hypochlorite solutions is preferred to machine dosing in higher concentrations.
- You can detect bleach damage by examining the strength of the individual yarns on a complaint item. Take out a single yarn, break it between your fingers and compare subjectively the breaking strength with that of a yarn from a new and unwashed item. If you suspect localised bleach damage caused by a bleach splash you may need to compare the strength of a yarn from an undamaged area with one near to a hole.
- The effect of bleach on the warp and the weft may be different and sometimes you will see characteristic holes which have a skein of warp threads with all the weft rotted away.
This is a typical stage in the development of a bleach damage hole.
- Cellulose fibres that have been damaged by bleach are much more sensitive to abrasion which is why fraying at the main wear edges can also be a useful symptom of bleach attack.
- On coloured fabrics the action of the bleach is slightly different on each component of a three component dye recipe. Red is often the least affected which is why blue towels which show bleach damage holes often have a pink tinge around the edge of the hole, which is a giveaway symptom.
Difference between soiling and staining
SOILING SITS ON THE YARN AND MUST BE WASHED OFF
STAINING DYES THE YARN AND MUST BE MADE COLOURLESS CHEMICALLY