Producing excellent results on cotton-rich fabrics

28 May 2015

With the right processing techniques, cotton-rich bedlinen can prove as acceptable to many users as 100% cotton. Richard Neale of LTC Worldwide gives his tips for producing high-quality results with this fabric

Most rental laundries in the UK now offer cotton-rich bedlinen rather than using only 100% cotton. The practice probably started around 2009/2010 when cotton shortages reached "crisis" levels and including polyester in fabrics gave a price advantage.
Now cotton-rich fabric can be seen as a good rental product in its own right as it has the potential to last much longer, with less risk of tear or burst damage, both in the laundry and during use in the guest room.
However, the inclusion of polyester is sometimes still seen as a negative in terms of quality but cotton-rich can be just as acceptable as pure cotton to the average user - indeed many cannot tell the difference until they are told that the fabric is a blend.
Success with cotton-rich fabrics starts with the right textile specification, but it is important to get the details right at every stage - washing, membrane pressing, conditioning and finally ironing. This is the only way to achieve perfection. It doesn't usually involve extra costs just the commitment to watching the fine details that marks out the true professional from the "wash and squash" merchant.

Textile specification
Suppliers offer both 70:30 and 80:20 blends of cotton-polyester, but laundries generally find a 70:30 blend slightly easier to process. Polyester makes the fabric much stronger than pure cotton and therefore less susceptible to chemical damage in washing, so the slightly higher content in a 70:30 blend can be an advantage.
It is important to specify that the cotton-polyester blend applies to both the warp and the weft of the fabric, with an intimate blend of both fibres in both directions. It is much cheaper to make a fabric with a spun cotton warp and a continuous filament polyester weft, but the high weft strength only improves the tear strength in one direction. So if the fabric is caught under a trolley wheel then it simply tears in the weakest direction and there is no net benefit in terms of textile life.
There is a relatively new European standard which is published by British Standards as a 'draft for development' as DD ENV 14237. This offers a specification for healthcare bedlinen but has also been found to be a useful benchmark for hospitality textiles. This document suggests a tensile strength in both warp and weft of 400N for good serviceability and a good cotton-rich cloth should have no problem meeting this specification without a cost penalty.
This is one of the keys to achieving a textile life in excess of 120 wash-and-use cycles, a level which is believed to be the average for rental pool-stock single sheets in the bulk market.
The life of double and king sheets falls to 110 cycles and 100 cycles respectively. This is very poor when the theoretical life of a 100% cotton sheet is 200 cycles if washed and finished correctly and the life of a cotton-rich item should be at least 50% higher than this!
The difference between actual and theoretical life is the result of abuse, accidental damage (yanking from under the trolley wheel or over enthusiastic bed-making), irremovable staining and progressive greying.
These problems can be minimised with careful management and attention to detail. Cotton-rich offers the opportunity, as yet unrealised, to reduce stock injection costs by at least 30%, which could make a considerable difference to the laundry's bottom line.

The cotton fibres in cotton-rich can be kept white and rendered stain-free by a standard process that starts with a cool pre-wash to soften protein stains and soiling. The main wash should then be at a temperature that is high enough to swell the cotton fibres and release the soiling and should have enough mechanical action to get the soiling clear and enough detergency to complete the removal and suspend the soiling in the wash liquor, so preventing greying.
However, the polyester fibres are highly oleophilic (oil-loving) and they trap the food oils, fatty food proteins, skin sebum and human body fluids that come into contact with the bedlinen. So they need a detergent with an adequate non-ionic content to break this oleophilic bond and get the fats and oils off the polyester fibres and into the wash liquor. If this is not achieved, then the remaining fats and oils will "set" and grey the polyester, giving the whole fabric a slightly dingy appearance.
If this problem is not dealt with swiftly, it will get worse with every wash and there is little chance of exceeding 120 wash-and-use cycles, as the fabric will become unacceptably grey. The problem will be even worse if there is insufficient suspending agent in the wash liquor because the soiling will then re-deposit onto the fibres and irreversibly compound the greying.
Whereas with a pure cotton fabric this problem can sometimes be countered by using a detergent with a good quality optical brightener (OBA), with cotton-rich fabric, the OBA will only bond to the cotton fibres, so the effect will only be 70% of what it would be on a 100% cotton.

Membrane pressing
Cotton-rich fabrics are usually strong so they can be designed to withstand a fast ramp-up to pressure in the membrane press. This allows the maximum pressure to be reached quickly and held for the maximum length of time.
Presses rated at 24 - 28bar, will need at least at least 60seconds at full pressure but this reduces progressively to 30seconds for pressures up to 56 bar.
Cotton-rich fabrics shed water more quickly than 100% cotton, so the moisture retention for sheets can be brought down towards 45%, which is low enough to allow the sheets to be ironed at maximum speeds if the ironer is in good condition.
Tuning the press to give optimum moisture retention is much more important for duvet covers and pillowcases, because these have to be ironed as two or even, with items such as mock-Oxford pillowcases, three layers of fabric.
This needs very careful tuning of the press and the engineer will need to go into the computer sequence and minimise the "wait" times if the residual moisture is higher than 40 - 45%.

The ideal is for fabrics to be conditioned in the tumble dryer for around 30seconds, just long enough to break the cheese of pressed textiles so that pieces can be pulled easily from the barrow, if a cheese-breaker or picker is not available.
Increasing the conditioning time to allow higher ironer speeds is a false economy. Ironers are usually quite energy-efficient (around 95%) but tumble dryers are unlikely to be much more than 50% efficient.
For laundries committed to reducing unit energy consumption by 7% year-on-year (to comply with the Climate Change Agreement), eliminating unnecessary dryer use is essential and very effective.
Optimising the press programs could take several hours, but the laundry will then need to spend more time optimising the ironer process.

The key to high efficiency on most laundry ironers comes from good training and strong leadership from the supervisor.
The first step is to get the bed coverage as near to 100% of what is possible in theory.
This means time spent getting edge- to-edge feeding, so that as work enters the first roll, the gap between pieces is as small as possible. This may mean setting the lay down so that the next piece is laid onto the feed bands with a few cm of overlap onto the trailing edge of the previous item.
This overlap will act as a drag on the trailing edge, improving presentation and the speed differential between the ironer and the feed bands will ensure that there is no overlap by the time the textiles enter the in-running nip.
The ironer needs to run steadily and continuously. There is no point in trying to run at a linear speed that is higher than the operators' feed rate with the result that work comes out with the occasional damp centre.
It is more important to maintain a steady rhythm, so that edge-to-edge feeding is the norm throughout the two hour run between breaks.
This requires a steady supply of full barrows to hand so that as one is emptied the next is in place without any gap. It also means that the arrangement of work in the barrows needs to allow pieces to be pulled free without undue yanking.
This in turns means that tumbler conditioning times must be long enough to untangle the work sufficiently. Operators are not machines and cannot be expected to work like automatons - they need to be rotated between tasks to avoid them becoming too stressed and so they have a variety of work.
Observing a well-run ironer line can be an education - it is surprising how much greater productivity can be obtained from a steady line running at a relatively low speed when compared with the irregularity and interruptions on one which is run slightly too fast and which actually produces fewer pieces per hour.

Shrinkage of cotton-rich fabrics
The correct ironer bed temperature for processing cotton-rich is the same as that for polyester-cotton.
Although the textile supplier will often label the item correctly (for ironing at 150C or with 4bar steam pressure), launderers have found that there are few problems with ironing up to 167C (or 6.5bar steam pressure from the boiler).
However if cotton-rich fabrics are ironed at over 167C, the polyester fibres in the cotton-rich fabric start to soften, and as a result they no longer add strength. The fabric starts to elongate slightly in the machine direction down the ironer, with the normal roll-to-roll stretch plus the drag of the textiles over the metal bed.
This elongation is not reversed in the next wash, as it would be with 100% cotton, and the piece gets progressively longer (by 0.5 - 1.0%).
Obviously regular waxing to control bed drag as far as possible, is even more important with cotton-rich than it is with 100% cotton.
Normal wash shrinkage with cotton-rich is under 5%, which is allowed for in the cutting out of sheets, duvet covers and pillowcases.
However, if a cotton-rich piece is ironed at too high a temperature, it can become progressively longer over the first 25 - 40 wash-and-use cycles until it is as much as 20% longer than it was originally.
As the piece gets longer it "necks-in" in the width, so it seems to shrink, although this is really distortion as the overall area does not reduce.
Avoiding too high an ironer temperature depends on the launderer's skill. It means following all of the tips in this article to produce linen which is white and stain free and which stays the correct shape.

REMEMBER THE BASICS: Handling cotton-rich labric successfully requires sound application of the basic principles of good washing



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