Perchloroethylene (perc)
Advantages: Perc is very well established as a drycleaning solvent and there is a wide range of suitable stain removal reagents and detergents. As a result, it can be used successfully with silks and delicates, with suedes and leathers and with heavy-soiled business suits and muddy items.
It is the most powerful retail drycleaning solvent in use, (90 on the kauri butanol (Kb) scale, which measures solvency). It is therefore ideal for the removal of heavy, oily staining and soiling. Its power gives it a clear edge when reducing stains that cannot safely be pre-treated.
Surprisingly, it has the lowest drying temperature of the three main solvents, so it can even be safely used to process modacrylic fun-fur (thermostat setting 40C).
Disadvantages: Perc will soften polystyrene beading, even when the beading has a protective coating, as the solvent enters the bead through the hole used for attaching it with thread.
This can reduce the decoration on an expensive wedding dress or ball gown to a sticky mess of “melted” plastic. Its power can make it equally damaging to polyurethane coated fabrics, when it enters the tiny stress cracks and can lift sections of the coating away.
From a safety viewpoint, perc is an anaesthetic, so it is important to dry bulky items thoroughly, otherwise they could prove to be dangerous if transported home in a poorly ventilated car.
Summary: Perc gives good results for cleaners who regularly take in heavily-soiled goods. It is particularly effective in removing engine grease and similar contamination. It is highly regarded by professional cleaners who value its power, but who also know how to control this strength when cleaning delicate items.
Hydrocarbon
Advantages: Hydrocarbon has a solvency power of only 30Kb so it has only one third the power of perc. In general, it will not damage polystyrene beads nor does it strip-out yarn oils from silk or cashmere so these fabric keep their handle.
It is odourless, so working conditions can be pleasanter.
Disadvantages: Hydrocarbon requires a high drying temperature, typically 60 – 65C, so be careful when drying heat-sensitive acrylics.
The lower solvency power means it may not be as effective as perc with heavily-soiled items. Although hydrocarbon does not usually damage coated fabrics, these must be dried thoroughly, as even a trace of solvent left on an item can cause nasty skin reactions.
Good machine maintenance is essential to stop bacteria and other micro-organisms breeding, leading to a stinking machine and smelly work.
Fire hazards have not proved to be significant in the many machines installed in the UK and Western Europe.
Summary: Hydrocarbon is relatively safe for beads and gives a superior finish on silks and cashmere. Stain pre-treatment is much more important and stain removal chemicals can be more difficult to flush from the cloth in the drycleaning machine.
Cyclosiloxanes
Advantages: This solvent is a pure chemical, which is used in cosmetics. It is odourless and generally regarded as very safe, despite recent Canadian concerns about bioaccumulation potential (see LCNi July 2).
The solvency power is around 20Kb so the risk of bead damage, or dye-bleed is minimal and it is a very good choice for delicate beadwork and trims as well as silks and angora. It produces a soft delicate finish and vibrant colours.
Disadvantages: This solvent is too low in solvency to remove heavy soiling. Stain removal reagents for this solvent have only recently been developed and can be more difficult to flush out, so stain removal requires more skill and care.
The drying temperature is 60 – 65C, so temperature sensitive goods require special care.
Summary: Cleaners who have made this choice work successfully have generally invested in stain-removal training. Trims can be cleaned without damage and customers are generally pleased with the results. It is especially good for delicate natural fabrics such as silk and mohair as it overcomes most of the associated problems and allows delicate and expensive designer items to be handled confidently.
