The simple answer to the question ‘can greying be avoided?’ is no, it can’t. While greying can occur in wetcleaning, with the exception of colour migration due to inadequate classification and/or detergency, it is mainly a problem confined to drycleaning. However, from a practical standpoint, provided the drycleaner has a good understanding of greying and in the case of an item that appears to be greyed on reception, brings this to the customer’s attention, it is unlikely to be a problem.
Greying occurs when particulate soiling or loose dye released during cleaning is redeposited on the textiles. It can be extremely difficult or impossible to remove but in a well-structured cleaning process with good detergency the amount of redeposition in drycleaning is so small it is quite unnoticeable and can only be measured/assessed by means of a reflectometer. Unfortunately, as greying is cumulative, with repeated drycleaning of white and pastel shades, very small amounts of accumulated greying may eventually become noticeable to the customer, leading to complaints of them looking dingy.
During drycleaning greasy soil particulates and others from direct contact and from atmospheric pollution are rapidly released by solvent and detergent action; if after release, these particulates are not removed rapidly from the vicinity of the garments some are likely to redeposit on the fibre surfaces where they become very firmly attached.
To minimise the risk of greying it is essential that the following risk factors are strictly controlled.
Classication
Poor classification is a very common cause of greying. White items in particular will be at risk if, say one, is included in a load of light garments, with the risk being greatly increased if included in a medium load. Coloured garments with white panels or white trim are at considerable risk of greying and cleaners should note that good classification demands that coloured items should always be classified in terms of their lightest colour so any with white panels or trim must be considered to be white. Make no mistake, if such items are included in other classifications and are greyed, it is the cleaner’s responsibility. It is also down to the cleaner if white items are discoloured by a coloured garment. There is no easy answer to this other than to accept the risk, clean the item on its own or, ideally, handwash or wetclean it if the care label allows.
Free moisture in the solvent
This is often characterised by a cloudy appearance and exposes textiles to a high risk of greying and shrinkage. Free moisture is attracted to some textiles and particularly to cellulosics such as cotton and linen; particulates, colour or dissolved impurities in the solvent may then be carried on to the load by the moisture and cause catastrophic greying. This explains why, in some cases, a white garment may grey noticeably while others in the load remain unaffected. Water based pre-spotting chemicals or damp patches from stain removal can also attract released soiling leaving a grey discolouration in the spotted area.
Process Structure
Pastel shades and whites are very much at risk if cleaned in a single circulating dip of distilled solvent without detergent as practiced by many cleaners. To reduce the risk of redeposition as far as possible it is vital that detergent is used and maintained at the dosage level recommended by the manufacturer as this promotes the removal of soiling, assists with its suspension and the control of moisture within the system. As the removed soiling needs to be removed quickly from the vicinity of the garments, the first stage of the process should be a wash from the base tank over the filter, followed by a rinse in distilled solvent to remove detergent. The filter must be producing crystal clear solvent before the process starts.
The following outline process structure is suitable for cleaning robust white loads in perc.
- 6 minute filter wash low dip using base tank solvent (solvent must be no more than a very light straw colour)
- Drain followed by short extract to still.
- 2 – 3 minute rinse in distilled solvent drain and final extract to base tank.
- Dry at a maximum air temperature of 60ºc
Removal of greying
If you are very lucky, depending on the fibre type, a reclean followed by a rinse in distilled solvent may restore the item. However, wetcleaning or washing offers a much better chance of success.
