Solvents may be classified by their by their ability to dissolve greases, oils and fats. The usual method of comparing the cleaning efficiency is by using the KBV (kauri-butanol value) scale of solvent categorisation. The higher the KBV number, the stronger the solvent and the spotting chemical trichloroethylene 130KBV is the highest value drycleaners are likely to encounter.

Perchloroethylene has a value of 90 KBV and the high cleaning efficiency of the solvent, coupled with its relative safety, has meant that it is the mainstay solvent of commercial drycleaning. It is relatively straightforward in use and is safe in that it does not catch fire or explode. It also has a good flushing action and pre-stain removal is fairly straightforward.

Removing oils

However, its efficiency in removing oils also makes it damaging to certain types of textile fibres and finishes. Fabrics or trimmings which use polyvinyl chloride (PVC), polycarbamide, polystyrene or polypropylene materials will be embrittled and hardened by perc. The cost of damaging a garment by inappropriate solvent immersion is usually laid at the feet of the drycleaner. Errors in application can prove costly as novel types of materials are usually associated with expensive designer or high-performance clothing.

The care of solvent-sensitive materials has necessitated the use of less aggressive solvents in drycleaning. For more than thirty years, chlorinated fluorocarbons (CFCs) were used in drycleaning where it was necessary to employ a solvent with a low KBV value. However, the environmental damage associated with CFC compounds has meant that a replacement for them had to be found.

Hydrocarbon solvents with a KBV value of about 30 have been gradually introduced as cleaning plant suitable for the containment of the solvent has been developed.

Milder than perc, hydrocarbon is not such an efficient degreaser. Pre-cleaning treatments have to be carried out with much more attention and often dry-side staining has to be totally removed before the garment can be cleaned. This solvent is particularly useful for cleaning silk and wool and delicate items such as wedding and ball gowns. Leathers also fair well.

Optional still

Machines are supplied with filters but a still is optional. Without a still, the solvent will tend to build up dissolved impurities and bacteria. A still involves additional expense, but the advantages generally outweigh the costs.

If a business handles only relatively clean work, then hydrocarbon may be the best answer. For greater soiling, perc will be the best choice.

The degree of mechanical action which can be applied to a textile is of huge importance. Some materials are highly susceptible to abrasion damage, pilling and shrinkage. Physical damage can be limited by enclosing a garment in a protective shroud but, more importantly, a reduction in the severity of the cleaning process can be the most beneficial.

The mixing of normal and sensitive materials in a cleaning machine is not recommended. As colour permanency cannot be guaranteed and various dyestuffs applied to textiles have different affinities for materials, it is also important that goods for cleaning are segregated with regard to their colour. Whilst colour-loss may not be prevented, the effects of colour transference from one garment to another can be minimised. In sorting loads, cleaners should also consider factors such as the degree of soiling. Oily or dirty garments should be treated with caution, especially in hydrocarbon cleaning.

Reputable supplier

Importantly, the solvents should be procured from a reputable supplier. The use of cheap solvent can be likened to putting cheap engine oil in a high-performance motor car, engine damage is likely to occur. Similarly, inferior, unstabilised, or recycled solvent will cause major problems to a drycleaning machine. Corrosion caused by impure solvent can invalidate the guarantees of machine suppliers.

Some drycleaners choose to use solvent alone when cleaning garments. However, if quality cleaning is to be achieved then the use of detergents is vital. Drycleaning detergents have the ability to capture particles of dirt and loose dyestuffs and carry them away to a machine’s filtration system or still. They also help carry free moisture through the system safely. A quality detergent used in conjunction with an appropriate cleaning programme will prevent particle redeposition, the cause of greying.

Because detergents are engineered for drycleaning, it is important that they are used within a wash programme at the right time and drycleaners need an awareness of how best to use the products available. Some are used at the first wash stage with a second one at the second wash stage, pre-wash and main wash. Second-stage cleaning detergents are available with retexturing agents, bacteriacides, or anti-static reducers.


The type of additives used by a cleaner will invariably reflect customers’ requirements. There are many additional treatments which drycleaners may be required to use on certain occasions. Reproofing of rainwear is probably the most common in the UK’s climate. This is best carried out in the machine, perhaps on a weekly basis. Rainwear is cleaned and then put to one side until sufficient items have been amassed to make it a viable proposition.

The garments are placed in the machine for a set programme, which usually consists of a pre-wash to remove detergents, followed by washing with the reproofing and then drying as normal. The application of treatment is now simplified as most modern drycleaning machines can be fitted with automatic pumps which carefully dispense accurate quantities of chemical compounds.

Stain-guards are specific treatments used to protect garments or textiles from absorbing water-based staining during use. They can also be used as reproofing agents. These types of treatment are becoming much more popular and even items such as ties can be stain guarded with excellent results. They attract an additional premium so are well worth considering. Most detergent suppliers will be able to advise you.

The additives must be injected at the correct stage in the cleaning process and your supplier should be capable of programming your machine so you obtain the best results.

When the items are re-cleaned, the stain guard will be washed off and should be replaced, as with reproofing. This means that the additive will pass into the still. It is essential that still maintenance is adhered to when these additives are used, otherwise films can build on the still walls and this will eventually slow the distillation.

Engineered chemicals

Drycleaning has come a long way in its 150 years. The range of engineered chemicals available to aid the cleaner is great and the machinery used is safe and reliable. In fact, the reliability of modern engineering and electronic control mechanisms has made it possible to develop novel cleaning systems, such as liquid carbon dioxide treatments.

However, whether this type of system will gain widespread popularity has yet to be seen. Other plant systems are currently examining the use of propylene glycol, Rynex.

If cleaners increase their knowledge of the systems and services available, they will find many ways of improving services to the customer and SATRA Technology Centre can provide answers to the cleaners’ problems. It provides many different training courses to help drycleaners improve their knowledge and understanding of both the processes and of the chemicals employed in cleaning.

The courses are modular in nature and some are specifically tailored to allow both employers and employees to attain industry qualifications in cleaning.

Effective cleaning

Different courses look at subjects such as the importance of process application in maintaining an effective cleaning plant, where the use of correct chemicals is reviewed as an imperative to ensure clothing is effectively cleaned and not damaged.

Health and safety awareness courses reaffirm the duty of care that attaches to using chemicals correctly.

Importantly, good practice reviews aim to ensure customer satisfaction and, in the longer term, reductions in running costs and increases in unit profitability.

One of the important features of the courses is that they give drycleaners an understanding of the limitations and uses of the chemicals which can be employed to achieve effective cleaning. Knowledge in this area also means cleaners can talk confidently about the processes and procedures they offer to customers.