Despite the impact of ever-rising cotton prices, demand for 100% cotton percale continues unabated.

This has produced significant problems for rental launderers, even the most technically proficient, but paying attention to detail at each stage of the laundry process, can produce superb results.

Solutions to some of the most common problems in handling cotton percale lie in examining first wash and checking details for tunnel washer processing, membrane pressing, conditioning, ironing, feeding and folding.

Definitions of cotton percale vary but if the number of threads per inch in the warp and the weft together total 200 or more, then this fabric is termed percale. The 200 thread count is traditionally the ultimate achievable with a

one-over-one plain weave. It is physically very difficult to pack in more yarns and still produce a fabric that is practical for use in textile rental.

Higher thread count fabrics are usually constructed using two yarns side-by-side for the warp and/or the weft. This method is called the double-pick insertion and the end result is a very fine cloth that is much prized by the boutique hotel trying to create a discernible difference in a competitive market place. The cloth may well be weaker than that produced by the conventional rental construction which it replaces and this can have a significant effect on the life cycle.

Cloth finish

Weaving efficiency and cloth price relates to the shuttle speed that will produce as many weft threads per minute as possible. To reduce the frictional heat of the travelling shuttle, the weaver coats the warp yarns with a sizing to reduce the coefficient of friction.

The warp sizing must then be removed by the launderer to avoid cracked ice creasing, which is created when the plastic size is crushed in the membrane press or during extraction in the washer-extractor. Sometimes the cloth finisher will apply sizing to the whole of the fabric to help stabilise the fabric and enhance the aesthetic appearance. This can create the same problems for the rental launderer as the warp sizing, so it must be removed at the same time, in the first wash.

Different sizings require different treatments and chemical suppliers are now getting equipped to offer the correct chemistry to remove sizing from any of the nine most popular groups.

This is always best done in a special process. If it is done in a continuous tunnel batch washer then it is best to batch-up the new stock and process it in one long run, each week or month.

Tunnel washer

Cotton percale can resemble parachute cloth in its impermeability. This is fine if you are baling out at 30,000ft but causes problems for the laundry that has to process ballooning duvets through a tunnel washer.

If the sizing has been successfully removed, launderers will have much more success; otherwise under-loading by 40% is the only way to minimise the risk of tunnel blockage. Users of top-transfer machines report far fewer problems with percale blockages than those with bottom transfer (which is the most popular design in the UK).

Membrane pressing

It is five times more expensive, in energy units, to iron a percale sheet dry than it is to squeeze out the moisture in the press so reducing squeezing times or pressures will carry a heavy cost penalty. The answer is to slow the ramp up to pressure as this will reduce the risk of a slug of water (which is incompressible) bursting the percale fabric balloon in which it is trapped.

Modern membrane presses are usually infinitely programmable and if the opportunity is also taken to tune the “wait” times in the press sequence, it is often possible to slow the ramp and still achieve adequate time at pressure – ideally 60 seconds for a 27 bar press.

If the tunnel washer uses warm rinsing, then pressure creases in the new percale will probably be much worse. This calls for detailed attention to the ironer, not reduced pressing. Whatever the moisture retention after pressing, it is a false economy to condition percale in the dryers for more than 30seconds or so.

It is far less costly to slow the ironer and go for maximum bed coverage instead – few ironers achieve more than 60 – 80%, so there is usually enough slack.

Prompt ironing

Percale must be ironed promptly to avoid drying out. A maximum of two barrows in the queue to each ironer feed station, with no overnight storage, is all that should be allowed.

If the fabric exhibits elasticity there will be a tendency for duvets and sheets to form either longitudinal creases down the central area or scallop creases down the edges. These can be minimised by reducing the feeder-to-ironer speed differential, the roll-to-roll speed differential and the ironer-to-folder speed differential.

If there is still undue stretching in the ironer, run the wax cloth at twice the frequency whilst ironing percale (to reduce the roll-to-bed drag and hence the stretch).

Even the best percale fabric, from which the warp sizing and the overall sizing has been successfully removed, will still exhibit cracked ice creasing if the roll-to-bed fit of every ironer roll is not perfect.

This means that every re-clothing must use exactly the right grade of cladding and after re-clothing, each roll should be “girthed” using the manufacturer’s girthing tapes to verify that the diameter is correct.

On some ironers the correct diameter is different for each roll. Only by attention to detail here will the cracked ice be removed.

The roll-to-bed fit should be achieved at a roll-to-bed pressure of around 3bar with fresh clothing, 3.2 metres wide (or proportionally higher pressures for wider ironers). The roll vacuum should be checked using an inexpensive vacuum gauge, testing a range of points across the width and around the diameter of each roll. Poor vacuum does not affect the pressure but it means that cracked ice creases will reappear at the folder stage. Poor joints in the vacuum system and wax accumulations in the ductwork and on the fan blades are the main problems and are easily cured.

Finally, check the clothing’s resilience, gauging its ability to take up double thickness hems without producing a poor finish in some areas.

Life cycle

Percale duvets are more fragile and more expensive than the older, more rugged rental constructions which they replace. They need protecting during their entire journey through the laundry, not just in the membrane press.

This means good transport roll cage discipline, with cages designed to protect the cloth from getting trapped in the locking mechanism, being spiked on loose wires or getting caught under cage wheels and picking up grime and grease from the vehicle’s walls or hoist.

Protecting the percale also requires superb handling disciplines in the laundry, with properly designed sorting facilities that prevent fabric falling on to the floor. The rule in the laundry must be that linen is never allowed to fall on to the floor. Just one black mark on a duvet means writing off a significant investment.

Getting co-operation from the hotel customer is just as essential. The customer service team should regularly check returning stock to identify mishandling and incorrect packaging/cage disciplines.

Modern rental laundries should be able to handle 100% cotton percale successfully. All it needs is good engineering, persistence and attention to detail.