High quality, heavier towels produced cost-effectively17 March 2021
Grey towels are a total turn off for hotel guests and Richard Neale of LTC Worldwide has been looking into methods to ensure your top-end towelling stays sparkling white for life
Despite the ravages of the present pandemic, there is still a desire, from four- and five-star hotels, for heavier, more luxurious towelling, which is stain-free, consistently soft to the touch and which stays a brilliant white throughout its life of (hopefully) at least 200+ wash and use cycles. Achieving this elusive target is by no means universal, with 120 cycles to failure (or disappearance) being the common and visible greying appearing half-way through a towel’s short life. This month we look at how to put this right – the simple keys to success.
Avoiding progressive greying
Greying occurs at two points in the laundry cycle – from re-deposition in the wash and from re-deposition in the dryer. Both are completely avoidable, by simple application of the craft skills of the professional launderer.
Re-deposition in the wash is mostly controlled by the suspending power of the detergent system which relies on the choice of suspending agent in the formulation and the dosage employed. (But, of course, there are other factors including poor emulsification, iron (FE++) contamination, hard water, turbidity and dye transfer from recycled water to name a few.) Modern premium detergents do not require over-dosing to negate greying. Of course, this assumes that the washer is correctly loaded, and optimisation of load-factor is discussed towards the end of this article. It is important not to skip this.
Re-deposition in the dryer is governed by the dryness endpoint for the load. If the textiles are taken to bone dry, then as they brush against each other and against the rotating cage, a tiny electrostatic charge is generated on the tip of the terry loop. This attracts every particle of dust and dirt from the drying airstream, causing progressive greying. This increases with every second of over-drying and it increases with every wash and use cycle, leading to the progressive greying which spoils so many circulating stocks. Controlling over-drying is discussed later in this article.
Current stain removal issues
There are two common sources of yellow/ brown stains currently appearing on hotel and spa towels. Many of these are caused by the disinfectant chlorhexidine which is used in some spa preparations and in some proprietary products. If this comes into contact with chlorine bleach, it forms an indelible yellow/brown mark. The only present solution is to switch to bleaching with hydrogen peroxide or peracetic acid.
The other annoying marks (also yellow/ brown) are caused by polyquaternium copolymers (‘polyquats’), which are used in some ‘all-in-one’ shampoo/bodywash formulations. These are colourless, but when they bond to the towel surface they attract and bind any loose soiling in the wash liquor to form what appears to be an indelible mark. In a previous issue of LCN (in August 2018), we reported on the release of research by Ecolab which has found that its product Turbo Colour Protect can now deal with this problem.
Many spa products contain essential oils and other ingredients which pose a challenge, even to the professional launderer. Washed towels often retain the odour of the treatments with which they were contaminated. After a time, they start to smell rancid and it is noted that they tear and go into holes very easily, resulting in a much shorter life. This raises important safety issues, because it is believed that failure to wash spa towels correctly can give rise to spontaneous combustion. Unremoved oils can start to oxidise with the heat in the dryer. This is a chemical reaction which is exothermic (it gives off heat) and if this occurs in a warm pile of incorrectly washed towels, the build-up of heat could cause the pile to ignite, sometimes hurling flaming towels over the immediate area.
One way of reducing this risk to a low level is to institute a dedicated wash process for spa textiles, based on an emulsifier designed to match the low HLB (hydrophilic-lipophilic balance) of the spa products. If this is done correctly then other benefits become apparent. Firstly, they no longer retain their scented odour after washing, secondly there is nothing left on them to go rancid and to smell unpleasant and thirdly, they yield a full life of up to 200 wash and use cycles, without tears and holes.
Creating tumble dryer capacity
There are two or three ways of creating extra tumbler capacity. Firstly, it is important not to waste tumbler minutes by unnecessary conditioning of flatwork prior to ironing. Flatwork for ironing should be dewatered as much as possible in the final spin or the membrane press, before being taken directly to the ironer from the washer extractor. For textiles processed in the tunnel washer, then time in the dryer should be limited to that just sufficient to break the ‘cheese’ from the membrane press. The savings in time from not over-drying, and from eliminating or minimising conditioning in the dryer will frequently free-up enough tumbler minutes to cope with an increase in towel weights to meet the latest customer demands. This not only saves the capital cost and disruption of not needing to install extra drying capacity; the reduction in running cost also offsets the extra gas needed to dry the heavier towels.
There are two factors to assess when deciding on the load factor for washing towels. Firstly, the washer and dryer must never be overloaded. It has to be accepted that the number of 650gsm towels might per load might never be as great as the number of say 500gsm ones. Having said this, the customer might accept heavier towels that are a few cm smaller in both width and length, which will offset the capacity problem partially. Overloading is taboo for several reasons and is never the key to countering the effects of increased towel weights. Overloading in the wash can reduce soil and stain removal, creating variable results for wash quality. It will also compromise re-deposition, leading to variable and progressive greying early in the towels’ life, because there will be an impact on suspending power (however good the detergent). So, what is the correct load factor? Cotton towels should be loaded to the manufacturer’s design weight for tunnel washers and at the rate of 1kg per 10 litre of cage capacity for washer extractors. This is based on dry weight, so it applies directly to new towels being given their pre-wash before first issue. For used towels, the weight of moisture they carry can be added on. This is usually in the region of 20%, which means that a 50kg tunnel washer could be loaded to 50kg + 20% = 60kg. To avoid any risk of overloading, it is a wise precaution to check the weight of a few batches of towels from the dryer, to verify that these are always around 50kg.
Overloading also has a detrimental effect in the dryer, because it prolongs the drying cycle and tends to create more variation, leading to some towels that are a little damper than others. This can be corrected by increasing the drying time, but this wastes energy and increases greying of those that were not damp. Regular daily checks on the dry weight can help to avoid both underloading and overloading.
The drying time depends on the initial moisture on content of the wet towels from the final spin or from the membrane press, so the first thing to do in creating more tumbler capacity is to minimise this. Extending the final spin time in half minute steps is one way of doing this for washer extractors, setting the spin time so that increasing the time by half a minute makes no further difference in moisture content. Tuning the membrane press to give at least 30 seconds at full pressure is a good rule of thumb for tunnel washer lines, although for older lower pressure presses 60+ seconds may be needed.
It is extremely difficult to achieve a consistent final moisture content of around 2% in the finished towels using manual settings for drying time. The best way is to invest in automatic cycle terminators, which use infra-red technology to measure the moisture percentage in the tumbling textiles themselves. The cost of these is relatively modest and can often be recovered within 12 months, from the energy savings alone. However, many laundries have found that the extra capacity created is even more valuable, together with the improvement in quality. Towels dried just down to the correct final moisture content stay whiter longer and are consistently softer to the touch.
The time is ripe just now to tackle towel capacity, because it closely linked to greying, to operating cost and to productivity, even without any desire to move to heavier towels. As laundry customers start to think about reopening their operations after lockdown, there could not be a better time. Good luck!
- If you have problem that you think LTC Worldwide can help with, or that you feel would make a good subject for Material Solutions, please call T: 00 44 (0) 816545