An important decision

SOLVENTS

1 May 2010



Richard Neale explains how the solvent choice can affect a cleaner’s work methods


A drycleaner’s choice of solvent should be determined by the mix of work as it may affect results and work methods may need adjusting.

Perc is the strongest solvent available to the retail cleaner, with a solvency power of 90Kauri-butanol (K-b). It is ideal for heavily soiled and stained fabrics. It also has the widest range of detergents and reagents.

Hydrocarbon has a solvency power of 30K-b, so stains, even oily ones, require more pre-treatment. However, its gentleness makes it kinder to silks and similar fabrics because it does not tend to remove the yarn oils so it preserves the much-valued “scrunch” and the sheen.

Cyclosiloxane with a solvency power of 12K-b, according to the website, is the mildest of these three solvents. It is ideal for dealing with beaded trims and materials such as PVC-coated cloths as the risk of solvent damage is usually minimal. It requires good stain pre-treatment skills as most stains must be either removed completely before machine processing or at least softened effectively. It is the best choice where the workload includes beaded wedding gowns, deep-dyed silk evening dresses, soft angoras and similar high-risk, high-value garments.

The other big difference between the solvents is drying temperature. Long term, perc machine development has successfully reduced this to a typical 45 – 50C air-off-the-cage, which is safe even for acrylic curtains. Only modacrylic fun-furs need a reduction in the drying thermostat setting.

Hydrocarbon and cyclosiloxane both need 60 – 65C air-off-the-cage for the drying airstream for normal goods. This should be reduced to 50C for temperature-sensitive fabrics and materials that are extremely sensitive to temperature can only withstand 40C so modacrylic fun-furs will need a much longer cycle.

Microbial growth is not normally a problem in perc, though it can occur. Routine cleaning is absolutely essential for hydrocarbon or cyclosiloxane machines as otherwise there is a considerable risk of bacterial growth and odours from bacterial excrement.

Loss of third tank brings problems

Problem: A cleaner with a three-tank perc machine changed to hydrocarbon and was persuaded (for cost reasons) that a two-tank machine would be sufficient. Unfortunately leathers and raincoats no longer met customer requirements.

Cause: While some leathers can be cleaned carefully in hydrocarbon without needing re-oiling this does not apply to all leathers. The loss of the third tank made machine re-oiling both difficult and wasteful. Similarly, raincoats still needed re-proofing and again the loss of the third tank made this much more difficult.

Responsibility: A two-tank machine has proved a false economy as a three-tank model would have allowed this skilled cleaner to continue to offer a wider service.

Rectification: Most high street cleaners now batch up rainwear for re-proofing and explain that this kind of specialist cleaning takes longer. Sub-contracting leather to a specialist is generally the best choice for all but the most talented. This cleaner could still continue to handle the original range of services but would have to send much more contaminated solvent to the still.

Oily marks need attention

Fault: The number of re-cleans for oily greasy marks rose steeply after the cleaner changed from perc to cyclosiloxane. Some needed three machine cleans.

Cause: Cyclosiloxane is not designed to remove heavy oils and greases on its own. The marks must be pre-treated with a solvent-based reagent to penetrate the grease’s long chain molecules. Repeated re-cleaning is not the answer.

Responsibility: The cleaner is responsible for stain removal. This type of mark is easy to treat with the right technique.

Rectification: The initial clean might have allowed some of the carbon particles to re-deposit locally onto the fabric but it should still be possible to remove the stain with a “dry-side” reagent, after appropriate pre-testing. It must then be re-cleaned (just once!).

Pre-treat collar and cuff grime

Fault: A switch from perc to hydrocarbon reduced complaints of faded and limp silks but brought far more about grimy collars and cuffs.

Cause: Pre-treatment detergent will soften collar and cuff grime so it all comes away in the machine process. Cleaners may get away with missing this vital step if they use perc but it is essential when using cyclosiloxane or hydrocarbon. You must use properly formulated pre-treatment detergent (thinly applied) to minimise colour damage risks. Machine detergent diluted with water is not suitable.

Responsibility: The cleaner is responsible for pre-treating grime.

Rectification: Applying the correct pre-treatment, tamping the dirtiest areas and then re-cleaning will usually cure the problem.

Don’t remove the spotting table

Fault: When this cleaner returned to perc after using hydrocarbon he thought he could manage without a spotting table. However he found there was a considerable increase in complaints about stains such as blackcurrant or coffee remaining on white sweaters and jackets.

Cause: No solvent can remove vegetable dyes such as these from textiles containing natural fibres such as angora or cotton. Vegetable colourings are very effective dyes that permanently colour the fabric. Such marks generally need pre-treatment with a mild bleach, which is why many tannin removers contain hydrogen peroxide.

Responsibility: The cleaner should take responsibility for treating such marks provided they can withstand either a simple tannin remover or a dilute solution of hydrogen peroxide.

Rectification: Vegetable dye stains should be as easy to remove after cleaning and pressing as before. The only factor that might prolong the process is the presence of sugars, for example in red-wine. These sugars need to be removed carefully with a steam gun or water flush before tackling the tannin stain itself.

Single filter increases greying

Fault: After a decade of careful cost cutting this cleaner replaced his two-filter machines with a single-filter model. Complaints of greying increased, even on single-bath delicate cycles.

Cause: Using two filters, one for darks the other for lights, acts as safeguard against discolouration and greying when programs are adjusted to minimise distilled solvent use. Copying the programs onto a single filter machine will remove this safeguard and increase greying risks.

Responsibility: Greying usually stems from dirty solvent, using too little detergent or failure to pre-dry cottons and wools. The cleaner is generally responsible. The only time a garment maker is to blame is when a contrasting garment is made with poorly dyed dark areas that bleed onto the pale areas or discolour the solvent.

Rectification: Greying is often very difficult or impossible to rectify. Washing in the correct detergent is sometimes successful. White garments that have greyed can sometimes be treated with either an oxidising or a reducing bleach but this requires considerable skill and special chemicals.


OILY MARKS OILY MARKS
THIRD TANK PROBLEM THIRD TANK PROBLEM
PRETREAT GRIME PRETREAT GRIME
SPOTTING SPOTTING
GREYING GREYING


Privacy Policy
We have updated our privacy policy. In the latest update it explains what cookies are and how we use them on our site. To learn more about cookies and their benefits, please view our privacy policy. Please be aware that parts of this site will not function correctly if you disable cookies. By continuing to use this site, you consent to our use of cookies in accordance with our privacy policy unless you have disabled them.