Material solutions

Making the right choice

1 November 2007



It is essential the right fabric be purchased at the start of any contract, says Ian Harris


An increasing number of laundry users such as hotels, nursing homes, restaurants and schools are asking the laundry service provider to buy and supply the textiles that they need. Choosing the right product can be a minefield for the unwary, but can make the difference between a profitable account and one that is a drain on resources.

For example, a 580g towel may cost £4.50 from one supplier and £6.75 from another. If you are budgeting to achieve 150 cycles to failure from the towel over a 24 month contract, the amortised cost per wash cycle will be in the region of 3.8p to 4.9p depending upon which towel is purchased and prevailing interest rates. But if the cheaper towel only lasts for 100 cycles, the amortised cost will be almost identical at 4.9p per cycle.

In addition, when deciding which towel to buy the following criteria should also be taken into account:

• fabric life;

• retention of colour;

• dimensional stability, including shrinkage and shape retention;

• processing methods;

• and processing costs.

The fabric life will depend upon a number of factors such as loss of pile through degradation in multiple laundering; pulling of threads causing “bald” areas on woven towels or ladders on poor quality knitted towels; holes and tears through loss of strength in multiple laundering; abuse by the user leading to irreversible staining, such as from make-up or shoe polish; and theft.

The tendency for the pile to degrade and be lost as lint in the wash or tumble dry stages depends on the length of the cellulose chain in the cotton. This in turn depends on the quality of the cotton used and the chemical damage to this in manufacture. This can be predicted by measuring the cuprammonium fluidity of the new cotton pile, provided this is 100% cotton and any polyester occurs only in the ground fabric.

If the pile contains even a small proportion of polyester then the life can only be predicted by experiment as part of the tear strength test.

To predict life expectancy, select a batch of 10 identical new towels. Remove one for measurement of tensile strength and keep it as the “control”.

Subject the batch to 25 commercial washes and remove a second towel for tensile strength measurement. Then give the remainder of the batch (eight towels) further 25 washes and remove another towel is removed.

Repeat until 10 readings have been obtained.Then plot the tensile strength versus number of washes.

The simplest way to compare towels from possible suppliers is to take a batch of 10 of each type of towel and wash these together, taking one of each type out after every 25 washes. The loss in strength of each towel type can then be plotted on the same graph.

The results can then be compared with standard performance ratings, such as those in the provisional European Norm prENV14237:2001 “Textiles in the healthcare sector”, which gives minimum strength requirements are given for both woven and knitted towels. Knitted towels are assessed by their burst pressure – minimum 600kPa warp and weft. Woven towels are tested for tensile strength – minimum 600N in warp and weft.

It is also advisable to run the trials both with and without bleach. The inclusion of polyester (which is unaffected by bleach) should give any towel a significant life advantage over a pure cotton one.

Although this test programme gives accurate results, it is time consuming. A more practical, but less accurate, method would be to wash all the sample towels together 25 times and then compare the strength of the cellulose chains with the results obtained on the new unwashed items. This can be done by measuring the cuprammonium fluidity of the cotton in each case. From this it is possible to project the life expectancy of the towel (see table).

Colour retention

There is often some performance variation between different colours so, if coloured towels are required, towels in two or three shades should be processed 25 times to assess the effect on the colour of processing:

• in a conventional detergent containing optical brightening agents;

• at high temperature (over 71C) to achieve thermal disinfection;

• with hypochlorite bleach;

• with hydrogen peroxide bleach.

White towels, especially those containing any polyester yarn content, should be assessed on how well they retain their whiteness and brightness after repeated laundry cycles with and without bleach.

Shrinkage

Many commercial laundries now use automatic or semi-automatic towel folding equipment and therefore the dimensional stability can have a major influence on the folding methods and presentation of the bundle of folded towels to the user.

Excessive shrinkage (or stretching) will affect not only the folding of the towel but also the acceptance by the user.

However, it is readily recognised that some relaxation and wash shrinkage will inevitably take place during the initial five laundry cycles. Most professional manufacturers and suppliers cater for this in the sizing of the articles during the “cut, make and trim (CMT)” manufacturing process.

Laundering methods

The launderer can either cause either greying or yellowing by incorrect washing or tumble drying. This can be exaggerated if the towel contains any polyester yarns. The key factors are degree of loading, detergent dosage, water hardness and detergent components (especially if work is heavily-soiled work or if the water is hard).

The washer-extractor should be loaded at 10 litre cage capacity per kg of dry towel.Tunnel washers should be loaded to 100% of the design batch weight. Heavily-soiled towels need enough detergent to get them clean, with sufficient suspending agent in the recipe to stop them going grey.

Over-drying in the tumbler creates a tiny static charge on the end of the bone-dry terry loops, attracting every particle from the drying air stream, causing progressive greying.

Processing costs

Although labour is the largest single cost in the laundry operation, the processing costs in terms of steam, water, chemicals and electricity are major factors. Of possibly greater importance is the effect on productivity/production.

Using towels with polyester in their construction will usually reduce drying times and energy costs. The increased tumbler productivity alone makes this valuable.

Although it is possible to conduct relevant comparison tests using one or two towels of each type, the potential margin for error is significant. Ideally, full 25kg batches of work should be assessed.

Assessing the types of towel can make save significant savings in time and money. For a 100 double-bed hotel with 80% occupancy and a weekly collection/delivery you can expect to process 291,200 towelling items.

A 2p saving in life expectancy could, over a 24 month contract, increase profits by £5,824, excluding savings in production and energy. With 20 similar customers, savings would rise to £116,480 – on just one classification! The same principles apply to all other classifications purchased.




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