50:50 vision is ideal when it comes to cotton-rich rentals

In many parts of the world, the textile rental industry still supplies 100% cotton because that is what the market demands. In others, the trend has been to 50:50 polyester cotton, because of the ease of processing and the longevity of the fabric. 100% cotton ticks all of the boxes for comfort for the sleeper in the bed, which is particularly important in hot and humid climates and even in the North European summer. However, it may well not last as long as 50:50 polycotton unless it is very well specified.
Polycotton looks very 'downmarket' when compared with the crisp, clean luxury and texture of pure cotton. Polycotton looks even worse if the launderer fails to control greying of white, cream and pastel shades.
In several major rental markets worldwide, the outcome of this dichotomy has been a rental sector for which the main textile is cotton-rich, mainly 70:30 cotton:polyester. The fibres are blended uniformly at the carding and spinning stage so that the long term strength of the polyester is available in both warp and weft, otherwise the high tear strength of polyester is lost (because under stress the fabric will tear in the weaker direction - the one with no polyester in it). The result is a fabric with a natural handle and texture, which 'breathes' well, but with the durability of its 50:50 polycotton competitor.
This month we look at the key techniques for success with cotton-rich and the reasons why so many users are not even aware that they have changed from 100% cotton. This advice includes techniques for getting the maximum benefits out of towelling, which uses polyester in the ground weave to improve towel strength and towel life.

Purchasing tips
Users of cotton-rich have found from experience that they can load cotton-rich by weight to exactly the same loading factor as 100% cotton, without encountering problems with tunnel washer blockage or poor soil removal. However, there is a proviso to this, which is that the fabric must be specified to be fully de-sized in cloth finishing. Otherwise brand new fabric can have such poor absorption characteristics that, when new, it can only be processed through a tunnel washer if it is under-loaded by 40%, which is uneconomic.
Each batch can be checked on delivery for adequate absorption by opening out one woven item on a flat table and placing one droplet of water on the horizontal cloth.
If the droplet is absorbed within three seconds, then the de-sizing has been adequate. If the fabric is impermeable and the droplet just sits there (or even if it disappears after 20 or 30 seconds) then there is a strong risk of blocking the tunnel in the first few washes.
If the membrane de-watering press at the end of the washing line delivers a good pressure (say 40 bar or more) then a fabric which has not been adequately de-sized is at risk of bursting, producing one sheet in every batch with a pattern of tiny single thread breaks over the area of a hand-span, which develop into unacceptable holes within three washes.
Fabric which has not been adequately de-sized can also develop 'cracked-ice' creasing, which the ironer will not remove (no matter how well it is tuned).

Classification
Best practice calls for cotton-rich and 100% cotton to be classified separately, so that the correct detergent blend and emulsifier can be used for each. Also, accidental inclusion of a coloured item (such as a coloured or paper napkin) will cause permanent damage to the cotton-rich items in the load. This is because the loose colour will be attracted very strongly to the dye sites on the polyester fibres, causing overall tinting at worst and overall greying at best.
This means that despite the inconvenience, there needs to be separate identification using different coloured side threads for 100% cotton and for cotton-rich, so that they can be classified into separate batches for washing and ironing.

Soil and stain removal
The polyester in cotton-rich is "oleophilic" or "oil-loving", which means it will attract and retain oily soiling from skin sebum, hair oils, cooking oils and spa treatments. It needs a different type of detergent mix from 100% cotton, calling for a blend which includes plenty of non-ionic surfactant, in addition to the normal anionic cleaning agents which are the work-horses in the blend. Many detergent suppliers also recommend a small dosage of emulsifier into the pre-wash, designed to solubilise and wrap up the oily soiling to prevent overall re-deposition later in the wash. A re-deposited layer of oily soiling, which might only be a few molecules thick, is all it takes to build up progressive and permanent greying and customer dissatisfaction.
It is tempting when faced with un-removed staining in the re-wash simply to increase the dosage of sodium hypochlorite into the rinse. This is not the right solution if the stains include retained oil or fatty proteins held by the polyester fibres. Firstly, it is unlikely to work (sodium hypochlorite is for vegetable dyes, not oil staining). Secondly, it will rot the cotton; the fact that polyester will resist bleach damage will not protect the cotton fibres. The cotton will be removed, so that eventually the blend will be reduced to 50:50 or even 30:70 and the strengthening effect of the polyester lost.

Dewatering
It should be quite possible to use the same maximum membrane press pressures for cotton-rich as for 100% cotton, without risk of bursting or irremovable creasing if the fabric is purchased to the correct specification. The moisture retention of cotton-rich is significantly lower than that of 100% cotton, so if the press will give 50% moisture retention for cotton it will achieve under 40% for cotton-rich.
This is important for three reasons: firstly, the amount of energy needed to evaporate one litre of water in the ironer is about five times the amount needed to squeeze it out in the press; it is about 15 times more to evaporate it in the tumble dryer. The cotton-rich will be much cheaper and easier to dry and finish.
Secondly, it enables the conditioning time in the dryer to be reduced to 30 seconds or so, just enough to break up the cheese for easy extraction for ironer feeding. This frees up tumble dryer minutes to increase towel drying capacity.
Thirdly, it enables the ironer to be operated at the correct bed temperature for cotton-rich, without excessive width shrinkage or distortion. The ironer can be run at the same speed as for 100% cotton but with the correct metal bed temperature.
Of course, it is only possible to use the maximum membrane press pressure for cotton-rich if the fabric has been fully de-sized. Otherwise, the cracked-ice creases cannot be removed by the ironer.

Sheeting products
Many customers now purchase sheeting products (including duvet covers and pillow cases) to a strength specification which calls for a tenacity of 400N warp and weft (as suggested in the draft standard for healthcare sheeting published by BSI as DD ENV 14237:2002).
This is believed to have made a major contribution to extending textile life from around 100 wash and use cycles up towards the 200 mark now being achieved by a few leading rental laundries.
The same improvements are theoretically possible with towelling. The draft BSI publication referred to also suggests a minimum tenacity for woven towelling of 300N warp and weft. The reason why the suggested specification for towelling is below that of sheeting is probably because there is more 'give' in towelling, so it is less likely to rupture if yanked roughly
The comments made earlier about intelligent process design for removal of oily, fatty stains also applies to towelling.

Conclusion
Cotton-rich offers substantial benefits (in cost, capacity and unit energy consumption) to the rental operator, but the full benefits are only realised by the adoption of best practice, following the key tips set out here.