Controlling holes, tears and residual staining

27 January 2016



Richard Neale of LTC Worldwide explains strategies that will help to minimise holes and tears, deal effectively with residual staining, and maximise textile life


There is a strong, though not obvious, link between minimising hole and tear damage and residual staining. This is because a standard method of reducing the amount residual stains is to increase the oxidisation in the process either by increasing bleach dosage or by allowing longer bleaching time.

Either solution will tend to shorten the life of any textile with a cotton or linen content as the bleach will start to rot the cotton as well as de-colouring the stain.
Bleaching in laundering should be designed to remove vegetable dye stains. It does this by oxidising the dye so that it becomes colourless.
This technique will also work on protein stains (from human body fluids and foods) but completely removing these stains needs much larger doses and longer times, so the effect on the textile is more severe. The bleach effectively chops the long cellulose polymer molecules in two, causing an immediate reduction in strength and ultimately in lifespan.
The strategies described here for controlling the holes and tears resulting from oxidisation and the techniques for removing protein stains without excessive bleaching will bring substantial benefits by extending textile life and so reducing stock costs. In plants that face yearly replacement costs of several hundred thousand pounds sterling, just 20% reduction will be significant.
That level can be easy to achieve and even saving a further 30% is not that difficult providing the business takes a disciplined approach. This involves taking precautionary measures in buying and receiving textiles and in wash processes.

Ordering and specifying textiles
British, European and international standards can assist greatly when ordering against a specification for strength and durability.
The BSI publication DD ENV 14237 is a draft European standard for healthcare textiles but it also works well for hospitality textiles. It provides draft specifications for tensile strength, wash shrinkage and many other features that affect durability.
The standard requires a minimum tensile strength of 400Newton in both warp and weft.
For 100% cottons it allows maximum wash shrinkage of 5% in warp and weft and for cotton-rich and polycottons, the maximum is 7%.
Sheets, duvet covers or pillowcases that meet this specification stand a good chance of lasting 200 wash and use cycles, providing the linen is not lost, stolen or abused.
All the launderer needs to do is to ensure that linens are not rotted or weakened by incorrect bleaching, over-souring or by abuse damage at the customers' premises.

Setting 12 month targets
Most rental linen only survives for 90 to 120 cycles (with hand towels lasting an average of 70), so a 20 cycles increase in life will achieve that initial 20% saving in stock costs.
If customers will accept cotton-rich rather than 100% cotton, achieving a high initial strength is much easier, particularly if over-bleaching might be an issue. Bleach does not have the same weakening effect on polyester as it does on cotton or linen.
A specification is still needed and eventually bleaching must still be controlled, otherwise the cotton fibres in a blend will rot away, leaving lightweight sheets consisting only of the remaining polyester.
Some customers have successfully ordered against a sample from the textile supplier. Before ordering in this way, the sample should be torn in both warp and weft directions to assess the initial resistance to abuse. It must also be washed and ironed five times to confirm its performance in ironing and its finished quality.
It is essential to keep a new unwashed and untorn reference sample both from those used for ordering and from each delivery afterwards.
This allows laundries to investigate disputes about quality if problems arise after delivered stock has gone into circulation. The reference samples should be kept for two years but can then go into stock.

Optimising wash processes
Best practice indicates that keeping the pre-wash below 40C prevents protein stains setting so they can be removed more easily.
Now only around half of UK laundries keep the pre-wash at this level but attempts to remove set proteins in the hot wash are unlikely to be successful.
The detergent supplier then has two options, either increase bleaching to burn the stains off chemically or use high levels of alkali in the hot wash. This approach shortens textile life significantly, hence the poor average figures quoted earlier.
Those laundries that do keep the
pre-wash below 40C have found that they only need to use the relatively small amount of bleach that will
de-colour vegetable dye stains, so the textile is stronger, the number of holes and tears reduces and textiles last much longer. Theft and abuse are then the main causes of early stock replacement.

Problems with sizing
When cotton prices rise, as they may well do in the near future, weavers come under pressure to control their costs by maximising the shuttle's speed across the loom.
To allow such high speeds, the warp yarns are pre-treated with a sizing that lowers the friction between the shuttle and weft yarns.
Polyvinyl alcohol (PVA) is one of the most effective ingredients of warp sizing and it is easily removed with a warm water wash when the cloth is de-sized. But, if the de-sizing is not thorough, any PVA left on the yarns sets firmly in the high temperatures used to "fix" the final finish in the stenter.
Once set the PVA becomes deformed and can only be removed with very high temperature washes containing very high alkali levels.
When new stock arrives in the laundry in this state it will take at least 20 washes before the sizing is finally removed through mechanical action.
Failure to remove such durable sizings before new stock is delivered can cause several problems. The set sizing makes linen impermeable so it will not wet-out properly and this may lead to tunnel washer blockages. The impermeability can also lead to slugs of water getting trapped in the linen, which in turn can lead to linen burst holes during the membrane press stage.
The set PVA can also lead to
cracked-ice creases that cannot usually be ironed out so that customers complain.
The best answer to such problems is to include a requirement for thorough de-sizing before delivery when specifying textiles, rather than just focussing on price and strength. The requirement should also be included when ordering against samples.

Typical holes: causes and solutions
Burst holes:
As mentioned above textiles (often new sheets) that have become impermeable through failure to remove sizing properly can suffer from burst holes when in the membrane press. This cause can be identified by a pattern of eight or nine tiny holes being grouped together over a hand-span sized area.
The best solution is to prevent it happening by putting new sheeting through a de-sizing process that will then allow it to be processed normally. This is usually carried out in a washer-extractor but seek your chemical supplier's advice on the exact process.
Alternatively, if the press is re-tuned to slow down the initial rate of increase in pressure, this will help to prevent the fault in the future.
As well as re-tuning the press, it may also be necessary to re-tune the "wait" times in the computer sequence to avoid reducing the textile's final moisture retention.

Holes caused by piercing
Puncture holes:
Textiles can be punctured in a variety of ways, each giving the holes a different appearance or pattern. A broken wire on a metal laundry cage can pierce small holes in the textiles. If this is the problem the holes are usually isolated, rather than appearing in the closely packed groups produced by a membrane press burst.
Bolt holes: Textiles can also get trapped in the bolt that fastens metal cages. This produces a larger puncture that is identifiable by its curved edge over a small radius.
Broken clips: Crocodile clips are used to join feeder or folder belts and if the clip is broken, one of the prongs will stand proud of the belt surface. If the fault is not noticed this prong can puncture holes in textiles travelling along the belt. This produces a single puncture hole in each affected item, but unlike a cage wire puncture, a crocodile clip puncture usually has a non-circular shape and often crosses the line of the weave.

Snags and tears
Identifying the cause of snag holes, and long or L-shaped tears can be difficult. The first step is to look at the point where the fault started. This is usually the corner of the L or in the middle of a long tear.
The faults might be caused by a puncture but often occur when linen is trapped in a feeder or folder or around a trolley wheel.
Wheel wraps and folder traps: Floor dirt ingrained around this point could indicate that this is a wheel wrap problem. If the area has traces of bearing oil, then the linen has probably been trapped in a folder.
Door and door lock traps: Ingrained marks of black rubber indicate that the textile has been trapped in a washer-extractor or freestanding tumble dryer. These marks come from the door seal.
A trap in the door lock of a washer will produce a characteristic indent. Test this theory by deliberately trapping a piece of scrap linen and then comparing the marks with those to be identified.
Abrasion holes: Holes caused by abrasion can be recognised by the damage to surface yarns, which often form parallel lines. Coloured, high density fibres embedded in the fluffed out ends of the broken cotton yarns will confirm that this is a "bag drag" problem. A sheet has been shaped into a bag to carry linen from the room or a duvet cover has been used for the same purpose. The "bag" of soiled linen has been dragged along carpeted corridors. This is the cause of the worst abrasion damage and where the "bag" picks up coloured carpet fibres.

Keep control
Controlling the amount of linen being scrapped because of hole or tear damage requires vigilance and a methodical approach -- looking for clues to the cause in each case.
This may be time consuming but it is the only way to increase linen life, reduce losses and save on replacement stock costs.

BLEACH/ACID: Splashes of acid or bleach have rotted and weakened the pile yarns on this towel. These yarns have been flushed away in the next wash to reveal the weakened but relatively undamaged ground weave. This can occur if the tunnel washer is stopped at the end on the day just after the bleach or sour injection

SPLASHES OF ACID


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