Greying

Maintaining the colour of a white or pastel is a challenge for many cleaners, but attention to detail will help to avoid the problem.

Even when a whites-only load is cleaned in pure distilled solvent, greying may still be a problem. Some fabrics, especially those containing cotton and wool, have properties that will attract the soiling particles removed by the solvent to redeposit. Any trace of moisture in the fabrics will increase the chance of this happening and just a few molecules of the soil will make the fabric look grey.

Drycleaning detergent is designed to prevent this redeposition by solubilising and suspending soiling, wrapping round each tiny molecule or element to hinder redeposition. Cationic detergents are attracted to the fabric and will form a physical barrier to redeposition. In addition, the detergent safely dissolves and disperses any free moisture that might otherwise cause greying. This includes the traces of humidity from the atmosphere, which cling to the fabric. The detergent may also help to disperse droplets of free moisture carried over into the distilled solvent in the water separator. However, there is a limit as to how much free moisture the detergent can handle, especially if the detergent dose is low.

Ideally, cleaners should take other precautions against greying and the detergent should only be expected to remove the last moisture traces. When sorting the loads, whites should be kept separate from pastels and neither class should be cleaned with medium or dark garments.

Some modern solvents (such as cyclosiloxane and hydrocarbon) are much more forgiving to mixed loads because of their lower solvency power, which also gives them a slightly better tolerance to free moisture.

Garments that contrast white/light colours with dark shades have the greatest potential for greying. Many garment makers do not understand the need for a much higher colourfastness tolerance for the darker parts of contrasting items. Fabrics with which a cleaner can cope with ease in a single colour, dark classification, by allowing the coloured solvent to go to the still for purification, are totally unsuitable for a striking black and white top. This is a problem that needs careful handling when the inevitable complaint comes in.

Reversing the result

Greying caused by redeposition of soiling from the cleaning fluid is very difficult to rectify, especially by re-cleaning. However, specialised wetcleaning (not washing) can often break the strong physical and chemical forces holding the greying matter onto the fabric. It is always worth trying but there is a risk that acetates, silks and sometimes viscose linings may crack, while wool and cottons may shrink.

These risks can be minimised by using the minimum mechanical action and letting the water in the process, aided by detergent, do the work. This requires a large-cage, programmable wetcleaning machine, set for few rotations and for extended dwell times. The detergent should be OBA-free so as not to damage pastels, including ivories and creams. If shrinkage is a risk, cleaners should not only minimise mechanical action but hang the garments to dry naturally – essential for wool, mohair, cashmere or angora. Measure such garments before cleaning so they can be brought back to size in finishing, panel by panel, using tension, steam and vacuum.