Keeping colours bright and fresh

15 August 2016



Richard Neale of LTC Worldwide says washing colours is a mix of good laundering practice and careful purchasing of the items


Textile rental operators and many of their customers much prefer white fabrics, because they can see every stain and any overall discoloration is immediately obvious. Even so, there are still a significant number of uses for which coloured items are essential to meet customer requirements, for bright bold colours which enliven the spa, pool or restaurant or which differentiate between various levels of supervisor and management.

Colours pose two problems for the rental operator. Firstly, they must be sufficiently colourfast as not to tint the whites if they are washed in successive batches in a tunnel washer (or if they are washed together in a washer-extractor). Secondly, they must stay the same colour within quite tight limits, without showing enough fade to make them look drab and prematurely old and without changing shade from say peach to pink or from bronze to green.

Sometimes, keeping colours bright and fresh simply calls for good laundering practices, but in most cases it is also essential to purchase correctly any item which uses even a tiny bit of coloured embroidery thread, fabric trim or fabric panels. Items involving different coloured components require much more care than items just in one uniform colour.

This month we look at the key techniques for guaranteeing good colourfastness and controlling any customer dissatisfaction down to a very low level.

Colourfastness

The textile must be colourfast to hot and cold water, so that it will not release dye if it encounters a spill from a glass of water or from a hot drink. This is vital for red and blue trim on white workwear, for example, used to differentiate a supervisor from an operative in the customer factory. This requirement is very different from that for a single coloured garment, because if a load of blue overalls bleeds out blue dye on the first wash this would not give any problems in a washer extractor and would be regarded as quite normal. The same is not true of blue coloured trim on a white coat.

The best suppliers of garments now recognise that they must use two different colourfastness standards when purchasing coloured fabric. They can manage quite adequately with a colourfastness to washing of Grade 4 on the International Grey Scale for Staining, with the same grade for shade change in washing. (The grey scale runs from 1=heavy staining or fading to 5=no staining or fading, in half point steps.) Grade 4 will give slight but visible colour fade in washing but the market expects this; if a white garment is accidentally included in the load then it will be tinted and ruined but it would rarely generate a justified complaint on the garment supplier.

For collar, cuff and pocket trim the requirement is very different. The colourfastness of coloured trim on a white garment calls for a colourfastness to washing of grey scale grade 5 for both colour change and staining. The reason for this is that a trace of, say, red dye goes a very long way and a supervisor is unlikely to be prepared to wear a pale pink garment when the workforce is in pristine white. Some suppliers get away with grey scale grade 4/5, but this often gives problems and complaint. Of course this makes the fabric much more expensive, but very little is used for trim, so the effect on garment cost is generally negligible.

The reason for the extra cost is because it is not possible to remove unattached dye from polyester fibres just by washing off in clear water. There are too many dye molecules loosely held to the cloth surface which do not come away. The solution is to use a ‘reduction clear’ stage at the end of dyeing and rinsing, which uses sodium dithionite and sodium hydroxide. The best suppliers of multi-coloured workwear have completely overcome the colourfastness problem.

Embroidery threads

For many years, accidental use of rayon thread was the only problem with maintaining colourfastness of embroidered logos on bed linen, towels and workwear. Rayon is difficult to dye so as to be adequately resistant to sodium hypochlorite bleach and as this is the main de-stainer in the textile rental sector it was not surprising that the level of colour fade and colour change with many shades of rayon thread led to serious and justified complaint. The best suppliers of polyester threads now use dyes which are resistant to all types of oxidising bleach including hypochlorite, provided this is dosed correctly and at the correct temperature.

Problems of colour fade (say from bright red to paler pink) and change in hue (say from bronze to green) have emerged in the last six years as a consequence of the trend to neutralisation in the final stage of the tunnel washer (instead of removal of wash chemistry by rinsing). There are often traces of wash chemicals left in the fabric after neutralisation, because it is so difficult to get the chemistry in perfect balance. It is not possible to dose an acid sour to give exactly pH7.0 = neutral, or to get the amount of anti-chlor precisely right, so as to cancel out traces of residual bleach.

The problems then come in the ironer, where the heated metal bed evaporates off the water, so that the trace amount of residual chemistry is then concentrated up in the moisture remaining, to a strength which causes colour damage. This effect is variable and unpredictable; it might occur only once or twice in say twenty washes, to the understandable puzzlement of the launderer. The best solution is to use embroidery threads which are resistant to trace amounts of laundry chemicals and tests have shown that 90% of polyester embroidery thread colourways do have adequate tolerance. The prime responsibility might lie with the launderer for leaving trace chemistry on the cloth, but the easiest solution lies in the hands of the embroiderer.

In some countries (Italy and the United States, for example) cotton threads rather than polyester ones are used, which are dyed with recipes designed to be very resistant to colour change in commercial laundering processes. The best of these are every bit as good as the best of the polyester threads. However, there are some colourways which can fade or change hue in the presence of any residual laundry chemistry resulting from imperfect neutralisation in the final stage of the tunnel washer. Again, about 90% give perfect results but the other 10% give marked changes under some conditions. When this appears to occur at random after some washes but not after every wash, one can appreciate the launderer’s bafflement (and the customer’s fury). Again the best solution is to check the threads to be used for adequate resistance to this type of laundry occurrence, even though the embroiderer might believe (rightly) that it is not their fault.

Causes of colour change

Coloured fabrics change colour as the result of exposure in use (to light, urine, perspiration, skin oils, alcohol and so on) as well as exposure to laundry chemicals (alkali, acid sours, oxidising bleaches and so on). This means that the best fabrics must be designed using dye recipes which are verified resistant to each of the groups of chemicals mentioned. International Standards provide an entire suite of test methods covering each of the different types of exposure mentioned, so it is not difficult to specify your requirement and to expect the fabric or garment supplier to be able to match this with justified assurance (in the form of a test certificate).

Exposure to spa oils is a particular problem for coloured towels, because many oils are difficult to remove (giving a problem which can be recognised by the rancid stench after a few washes). Unfortunately, the un-removed oils and other ingredients tend to oxidise by chemical reaction with the oxygen in the air, accelerated by heat in the tumble dryer. The breakdown products created frequently either rot the towel (so that it tears easily) or they change the colour (so that the towel becomes patchy).

The solution to this is to wash spa towels in a process which removes all of the oils in a single normal wash and the leading detergent suppliers now have processes which will achieve this, even in tunnel washers.

Conclusion

Each of the potential problems featured in this article can now be designed out at the ordering stage, simply by specifying to the various suppliers exactly what is required. They are not difficult to solve, but they do require forethought and careful planning. There is no overall standard to which rental operators can refer for fitness for purpose as regards many types of colourfastness, so if disaster occurs as the result of inadequate specification it can be difficult to get redress or refund. It is far better to get it right in the first place!

 

 

POOR RINSING OF BLEACH


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