Richard Neale of the Laundry Technology Centre explains the risks posed by handling Spa towels and suggests how launderers can avoid these as much as possible
Spa towels often carry residues from the skin care products used in treatments and these residues can, if not removed properly, can pose a safety risk or lead to expensive damage to stock. There are three main problems:
– Fire risks
– Unusual holes in "young" towels
– Indelible brown stains
Unfortunately, the towels often appear unstained when they arrive in the sorting area and so potential problems go unnoticed and untreated until much circulating stock has been damaged and the need for action is clear.
The potential risks of this category must be addressed with systems and wash processes that are suitable for busy, high volume rental laundries.
This is not easy but all leading detergent suppliers have the right technology and if problems are identified early in the wash house system then solutions can be put in place. The effect on overall quality, productivity, reduced fire risk and reduced textile costs can be dramatic.
Explaining the risks
Essential oils such as cloves, eucalyptus and similar products are a main feature of spa treatments.
In their pure form many of these essential oils would be classed as flammable liquids with flash points in the range 50 – 60C. The product formula usually dilutes them in a carrier oil at a concentration of 0.5 to 3%, so the final flammability depends to a large extent on the carrier being used. However, the essential oils do not dissolve in or mix with water, so the carrier oils are likely to be well able to support combustion once ignited. Essential oils are exceptionally difficult to wash out of towels, either partially or completely, so the residues remains on the wet towels when they go from washer to dryer.
Once the water has evaporated, the towel warms up and many oils will start to react with the oxygen in the drying airstream and give off heat. This (exothermic) reaction continues when the towels are unloaded into a barrow, although at this point any heat generated usually (but not always) dissipates naturally. The towels then pass to the towel folder where they are folded and stacked.
If the reaction continues, heat builds up in the centre of one or more of the stacks and the surrounding towels insulate it and prevent it dissipating. As the temperature of the centre rises the reaction develops faster and faster until eventually the whole stack ignites, exploding and hurling flaming textiles all over the laundry.
This has been advanced as one of the main reasons for the unexplained laundry fires that break out in the middle of the night.
In most laundries there are no staff on site overnight to deal with the problem so the whole laundry can burn down leading to a typical insurance bill of £5million – £10million each time.
Currently the UK laundry and rental sector loses one or two laundries a year through fire. The most likely common factor in this scenario is un-removed oil on the textiles at the seat of the blaze.
Spa towels that have not been properly washed usually smell, either of hot essential oils, if the staining is recent, or of the oils’ foul and rancid breakdown products if the contamination has been left to build.
Laundries should regard such odours as a sign of developing problems and take action. If the wash process is doing its job then there should be no residual oils and no odours.
The odour problem underlines the difficulty of removing these oils in a standard wash. They need not only good detergency and plenty of alkali, but also the correct emulsifier at a good dosage. The oils will then be removed with a main wash temperature of 75C (which is needed for disinfection in any case). The process can be carried out in a washer-extractor or a tunnel washer, the secret is in the chemistry not the machine.
The emulsifier is the most important ingredient in a specific essential oil treatment. It must have an HLB value similar to that of the essential oil being removed. The HLB value defines the hydrophilic lipophilic balance and hence the relative solubility of the oil to be removed.
Typical HLB values for essential oils can be as low as 7 and even lower. To put this into context, many emulsifiers designed for engineers’ oily work-wear need an HLB value of 14 – 15, which is unlikely to remove eucalyptus oil completely or even adequately.
If the emulsifier has an HLB range which spans the oils’ HLB values, then it should give complete removal (provided the detergency and alkali have also been optimised).
Towels with essential oil residues need higher detergent doses – up to double the dose used for a standard towel wash.
Sodium metasilicate is probably the best alkali for this application but it might not be possible for liquid feeds (in which case potassium hydroxide or sodium hydroxide are preferable to weaker alkali builders such as sodium carbonate).
The thermal breakdown products of many essential oils are acidic and they will rot cotton towels very quickly. This results in holes appearing prematurely in relatively young towels.
The yarns around the hole’s edges will be very weak, while those in the rest of the towel will be much stronger.
The cause can be confirmed quite accurately by applying Sudan Red indicator and examining the towel under UV light.
If there are essential oil residues, the dye will adhere to these, identifying and showing the extent of the staining.
If oxidation of un-removed essential oils has led to holes in one towel, then urgent action is needed, because almost certainly, similar damage will be developing in the rest of the circulating stock.
Essential oils can also be accompanied by brown staining, which resists all attempts at removal by heavy bleaching or even by the use of a reducing agent such as sodium dithionite.
Marking of this type, which survives a re-wash, so it is unlikely to be protein-based, could be caused by rust or by chlorhexidine, a disinfectant used in many skin products and certainly in some essential oil treatments.
Unfortunately chlorhexidine reacts with chlorine bleach in laundering to form an indelible dye. It is the most likely culprit if spa towels have been indelibly stained.
Stains: The following procedure is recommended for recovering as many still-stained towels as possible.
1: Sort-out those towels that are still stained at the towel folder into re-wash.
2. The re-wash must use a dedicated one-stage process at high temperature. The process should include an alkali booster and enhanced bleaching. A washer-extractor process will give a higher recovery rate (because the enhanced chemistry will not disappear into other compartments on the tunnel washer).
3. After this re-wash sort the load again. Put the unstained pile back into circulation and put the towels that still have residual staining into a washer-extractor and run an iron removal process.
4: Finally scrap any towels that are still stained.
This procedure will deal with oxidised protein staining (which should be removable in a well-designed
re-wash) and rust marks (which will come out in the final recovery wash). However, it will not deal with the hazards of essential oils unless the re-wash includes the right range of emulsifiers.
Fires and holes: If the launderer removes the essential oils completely in the normal wash (by incorporating the correct dose of a well-researched emulsifier, good detergency and an alkali booster) then there will be no oxidation in the dryer and the fire risk will be very low. This means re-designing the normal towel process, because most standard towel washes do not take out enough of the staining caused by essential oils and similar products. The residual aroma gets more pungent and obnoxious as the essential oils are degraded in the dryer. This is an early warning of the fire risk and the risk can only be reduced by attention to the wash process.
Improving the cool-down and emptying the dryers every night is only tinkering with the symptoms, adjusting the wash is the essential to tackle this risk.
Reducing fire risks is so important that it must start with the normal wash must be fortified with the correct emulsifier and other features.
Fortunately, the detergent suppliers are right up with the latest technology for fire prevention by good washing and particularly by the use of emulsifiers which can be hand picked to meet the different demands of work-wear and spa oils.
With a concerted effort there is now the knowledge available to make laundry fires from un-removed oils a hazard of the past.
Indelible chlorhexidine marking: If these marks become a significant problem then the only satisfactory solution is to change the bleach method from sodium hypochlorite to hydrogen peroxide (which is more expensive).
The healthcare laundering sector has largely done this, either with hydrogen peroxide directly or with a peroxide generator such as sodium percarbonate or peracetic acid.
Otherwise the method for dealing with still-stained towels given earlier will enable rapid identification and scrapping of towels with chlorhexidine staining. This will minimise the number of loads that are repeatedly sent to
re-wash and increase the laundry’s costs without bringing any improvement.
It is expected that, with the increasing uptake of skin preparations both domestically and in commercial spa treatments, the incidence of chlorhexidine staining on hospitality work will continue to increase.
Putting in place the correct solutions to remove difficult staining, as described in this article, will not only improve the appearance and odour of many towelling products but it will also greatly improve laundry safety with respect to fires which break out unexpectedly in the middle of the night.
These procedures should now be forming an integral part of the launderer’s standard fire prevention measures.