Material solutions

Checking that new stock meets expectations

1 June 2011



Ian Harris explains the importance of correctly specifying stock and checking it when it comes into the laundry


Most laundries have to handle new textile stock on a fairly regular basis. Even the best quality linen will eventually need to be replaced – for example, because it has started to disintegrate or is permanently discoloured or stained or has turned grey.

This new stock will either have been bought by the laundry’s customer and sent in for processing or it will have been specified and purchased by the laundry for use in rental contracts.

No matter who has purchased the textiles, everyone involved will have certain expectations.

The laundry will be concerned about how easily the textiles can be handled and processed and may also expect them to last for a defined period of time.

The customer may expect them to maintain their appearance and, in the case of bed- or table-linen be easy to handle or, in the case of uniforms or workwear, be comfortable and practical to wear and work in. If the customer has bought the linen, they may also have expectations of how long it will last.

Specification

Before textiles are purchased those responsible for selecting and buying them should have taken three key steps to ensure textiles meet expectations.

The buyer must produce a textile specification for the quality of fabric. They must also produce a specification for the finished goods, which should cover cutting out, sizing, hemming and stitching. As a last stage buyers should obtain validation that the purchased textiles meet the specifications.

Unfortunately not all textile buyers specify the textiles either correctly or adequately. This may apply both to customers buying their own textiles for laundering and to laundries that buy textiles for rental contracts.

Even so, when the laundry receives new stock it is essential that this is checked to see whether it is fit for purpose and whether it can withstand the laundry processes without any serious problems.

Checking choice

There are two main options for checking and it is up to the management/executive how the checking proceeds. Option 1 is to retain samples of each classification from the consignment and store them un-processed in a secure location.

Option 2 is to take samples and to put them through at least three, and ideally 25, laundry wash and dry cycles before sending them off for a range of laboratory tests so that the results can be assessed against the original specified requirements appropriate to the end-use of the fabric.

Batch codes

Irrespective of which option the management chooses, the supervisor carrying it out should note that each consignment of goods received will always have a manufacturer’s coding that identifies each batch of fabric with a unique sequence (often only identifiable to that company) to indicate when and where it was manufactured.

Even though the laundry may not understand the batch code, it is essential to take samples from each batch within a consignment as there are often variations from batch-to-batch.

If the laundry chooses the first option, the samples from each classification taken from each batch should be clearly labelled, re-packaged and stored in a suitable location. They must be kept for at least six months and ideally for 12 months from the date the new stock was placed into circulation.

Identification

It is also essential that the new stock that goes into circulation is clearly and readily identifiable. Then if anything does go wrong, it can be easily withdrawn from the system. Even then it is a logistical nightmare if, for example, a new consignment of duvet covers shrinks excessively in the width and it is necessary to isolate and withdraw 1,000 new stock covers from a total pool circulating stock of 100,000.

Many laundries will make weekly or monthly stock injections as old stock is withdrawn, so that the circulating stock is topped-up with new stock on an on-going basis. Marking and identifying each stock injection can become a time-consuming and laborious task. However, failure to do this can result in a continuous stream of user complaints.

Additional benefits

Identifying each injection of stock can have an additional benefit as it will then be relatively easy to identify the age of each item in circulation. Then if an excessive number of young stock starts to appear in the laundry’s rags this will act as a warning that one particular batch is failing to achieve its target life expectancy.

If the management decides on the second checking option, the laundry will have to take samples of each classification from each batch of the consignment and examine and test them before any of the stock goes into circulation.

The range of tests will be largely dictated by the quality of the original purchase specification given to the manufacturers or, in the absence of any company specification, the specification given by the manufacturers.

Essential tests

The three checks given here represent those that are absolutely essential.

Shrinkage: The new unwashed samples should be measured and the results recorded. They should then be put through at least three and ideally 25 wash and dry cycles, then re-measured. The measurements can then be compared with the original to obtain the percentage dimensional change. The management will then have to decide whether the results are acceptable.

Strength: The type of test may vary somewhat depending upon the fibre content. For example, for a 100% cotton item a cuprammonium fluidity test should be completed on a new unwashed sample and the test then repeated on the same sample after it has been washed 25 times.

The test house will give the results of this test in either reciprocal poise (rp) or degree of polymerisation. UK companies tend to use reciprocal poise and the new fabric should be in the range of 3 – 5rp. If the new unwashed fabric has a reciprocal poise value that is greater than 5rp, it is highly likely that the textile mill has over-bleached the fabric during manufacture and this will reduce the target life expectancy proportionally.

In a well managed laundry, 25 washes – with normal bleaching – should produce no more than a 3rp increase in fluidity. Increases greater than 3rp indicate that there is a potential problem with the wash processes and these should be reviewed if fabric life expectancy is to be achieved.

Polycotton blends require a tear-strength test. Again, a new unwashed sample should be assessed against the same sample after it has been washed 25 times to determine how much fabric strength is lost during the wash processing.

The minimum basic requirement on the new unwashed fabric is a tear strength of 400 Newton in both the warp and weft. This should be measured using the strip method given in EN/ISO13934-1.

After 25 wash and dry cycles in the laundry test, the fabric should not have suffered more than a 12% loss in strength so the strength should still exceed 364 Newton after 25 washes.

Pilling tests: Pilling occurs as a result of either insufficient twist being put into the yarns used to weave the fabric or the staple filament fibre length being too short. This means that, especially in areas of the fabric that are likely to be used most or subject to friction, fibres work loose from the individual yarns and roll into little balls that are frequently attached firmly to the cloth by just one or two fibres.

As a result the item can be extremely uncomfortable to handle or wear, especially if it is in direct contact with the skin, which can lead to sores and reddened patches. In some cases an item with pilling may be so uncomfortable that it cannot be used even though the fabric may still be inherently strong and have many more months of service left in it.

As with all the other tests, the pilling test should be undertaken on samples of new and unwashed fabric and then again on the same samples after washing 25 times. Once all of the fabric dressing has been removed through multiple washes and the fibres are no longer effectively “glued” to the yarns, a true pilling result can be obtained.

Additional tests

There are several other tests that can be carried out to minimise the risk of problems in the future.

Colourfastness to light, washing, bleaches and optical brightening agents: Hotels and restaurants will be upset if when all the tables are laid, a manager finds that each cloth or napkin has a slightly different shade.

Choice of stitching thread, stitch design, stitch tension, hem design and seam design: If any of these factors are wrong it can cause excessive puckering (seam tension too high), seams coming open (insufficient stitches per cm or per inch depending on the wording of the specification) or the stitching turning grey whilst the fabric is white (Incorrect sewing thread used).

Allowance for stitch bite in seam and hem design: An inadequate seam allowance often leads to frayed edges on towels. The side hems open to reveal the raw cut edge of the fabric which then frays readily.

Bar tacks and reinforcing of high tension areas: These need to be checked to see that they are placed correctly and that they are strong enough to ensure that the fabric does not split down the seam when the item is used repeatedly. For example, this fault can occur in duvet covers when the side seams come under tension.

Fabric mass, weight of yarn and number of threads per cm, warp and weft: The price paid for any textile is based upon the weight of yarn used (measured in tex) to produce the fabric and on the number of threads per inch (tpi).**

The weight affects the cost, especially when cotton is in short supply as at present.

The number of warp threads affects the spinning and beaming costs. The number of weft threads affects the weaving cost.

For example, a material could have a 200 thread count (which could be made up of 110 warp threads and 90 weft threads per inch). If a 40 tex yarn is used, the mass of the fabric can be readily calculated and should be approximately 315g/m2.

The three components, i.e. thread count, fabric mass and yarn tex are all inter-dependant and if any two of the components are known, then the third can be calculated.

Weighing the options

Choosing which option to take to control stock injections must be a management decision, taken in consultation with the user. The risks of introducing faulty or sub-standard stock into circulation include consequent customer complaints and the costs associated with early withdrawal and replacement.

These risks need to be weighed carefully against the costs of testing and the time needed to complete all the necessary test work, possibly 2 – 3 weeks, before introducing the new stock into the system.

In today’s highly competitive market, the risks of losing customers are high if any aspect of the service falls short of their expectations.

When these are coupled with the steep increases in the cost of the textiles themselves, there is now a sound case for planning and managing stock injections carefully.

Checking that the goods delivered meet the laundry’s specifications is becoming essential when accepting deliveries worth many tens of thousands of pounds. Once new stock is injected the problems of extracting this and then gaining compensation for any mistakes become ten times greater.

**NB: Unless otherwise indicated thread counts are always given in threads per inch (tpi) although other figures are given in metric measurements




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