Into the blue

My involvement with denim garment washing began in 1986. At that time, it seemed that washing was more of an art, relying heavily on the traditional skills of the laundry operator.

My impression, ten years on, is that it is now more of a science, where traditional skills have been largely superseded by modern sophisticated equipment, and greater scientific controls.

What sort of changes have taken place, and have they all been for the good of the industry, and beneficial to the consumer?

To answer that, one has to go back to 1986 and trace the various developments that have occurred since then. These include:

• Variations in washed fashion appearances.

• Improvements in machinery to produce these fashions.

• Development of chemicals to facilitate washed appearance.

• The advent of new fibres introduced to stimulate trade growth.

Washed fashions

This factor is primarily responsible for changes in washing procedures and washing machinery, most notably in stonewashing and bleaching.

In 1986, the preferred appearance was for dark, indigo colours, with only a modest amount of abrasion.

Bleaching down to mid-blue shades was just becoming popular and soon led to heavy bleaching to obtain the very light superbleach colours.

Denim appearances underwent a complete revolution during the early part of 1988 when, in an attempt to infuse new life into a very static period of sales, the so-called “marble” and “snow” washes were introduced.

The new technique involved dry washing garments with pumice stones saturated with permanganate or hypo-chlorite solution.

The impact of a bleach-saturated stone on an unwashed indigo dyed garment produced an immediate reduction in colour which, on completion of anti-chlor and other finishing wash treatments, produced an endless variety of marbled effects which duplicated severe abrasion washes.

The only other significant change imposed by fashion since then has been the introduction of coloured denim garments. This has flourished fairly steadily since 1993, commencing with overdyes in blue and black, and graduating to all colours of the rainbow. These are not normally stonewashed, and shades of traditional blue are still the most popular denim colours. It has to be said, however, that another radical change in washed appearances is overdue.

Improved machines

Stonewashing in 1986 was extremely crude. Pumice stones were used in large amounts and remained with the garments throughout the wash. Machinery was largely adapted to stonewash with small Planet machines doing a great deal of the work.

These were strong, rugged machines, many of them second-hand, and considered expendable.

The industry was in the denim doldrums during 1987-88. The market was stagnant: a new fashion stimulus was needed. This came with the new marble washes, and the small Planet washers were the only machines to hand that could adapt readily to this most hostile of all denim washes.

Such small washers could only produce small wash lot sizes which meant a lack of consistency in finishes, low production and thereby greater costs. In some cases, laundries could charge up to £3/garment.

Barrel machines appeared towards the end of 1988. These were especially designed to handle the marble style washes. The very first machines could only handle the “dry” stonewashes.

A further development produced machines that could also provide aqueous stonewashes.

The craze for marble washes only lasted two fashion seasons. The main reason for its demise was probably due to so many cowboys jumping on the bandwagon and turning out poor quality work from inadequate machinery. This style of wash has not reappeared in the UK, but is still being produced in the US and the Far East.

Around the same time that the aqueous barrel washers were introduced, there were developments in continuous batch washers.

Laundries engaged in high volume production of jeans for such outlets as Levis and Lee found that it was possible to modify certain tunnel washers and carry out a large-scale desizing operation.

Whatever the claims, only the largest of denim washing businesses could afford such large capital outlay and by 1993 even those companies had found disadvantages that directed them back to desizing in barrel machines and completing the washes in washer-extractors.

The big problem with barrel machines has always been unloading them and then separating out the stones before passing to the final washing operations. Since they were unable to hydro-extract, the unloading operation was very messy, dirty and laborious.

During the past two years, a new generation of washers has been developed that have been designed to compromise bet-ween barrel machines and low-extract washer-extractors.

With a loading capacity and large volume cage size comparable to barrel machines, they are able to rinse and hydro-extract at low speeds of between 140-160 rpm. This is sufficient to get rid of surface water, and so make the handling procedures much less messy. The traditional barrel machines of the late 1980s are now considered obsolete.

As far as traditional washer-extractors are concerned, basic design has remained the same. The main differences are merely in their larger rated capacities, and more sophisticated control systems. All new machines come equipped with microprocessor controls, which can be linked to a master control that can tell the laundry manager at the touch of a button exactly what every machine is doing.

Some machines can calculate the correct liquor ratio to weight of load, ensuring accuracy of conditions from wash load to wash load, and most have pH sampling facilities. Variable speed drives are now offered which increase flexibility.

For the larger wash load sizes now possible, most machines have tilting facilities to make loading and unloading easier. Most are readily adaptable to automatic chemical dosage systems.

With washers equipped to this degree, the work of the laundry operative is largely reduced to loading and unloading machines, and there is much more scientific control over processing. The development of larger, more sophisticated washing machinery had to be matched by advances in drying equipment.

At the beginning of the decade, all denim garments were tumbled dried in steam-heated tumblers, the majority of which were of 50 kg capacity and with little more than a temperature gauge and a simple timer.

In 1996, there was an increasing number of gas-fired dryers, and with capacity to take 200 kg loads. These machines came complete with microprocessor controlled operation of a variety of programmes and with accurate temperature and residual moisture controls.

Automatic lint removal was an innovative option on such machines, and some of them could dry large wash lot sizes of jeans in half the time it used to take to dry a 50 kg load.

The introduction of live steam chambers has created the possibility of drying and steam finishing garments on hangers.

It is eventually hoped to produce garments that will either not require final pressing, or be more presentable and easier to press.

Chemical changes

While machinery manufacturers were busy building bigger and better washers and dryers, the chemical suppliers had not been idle. The most significant development was the introduction in 1989 of cellulase enzyme products.

These enzymes revolutionised stone-washing practice. They had the unique property of being able to digest cellulose particles. In doing so, they also degraded the indigo dye on the surface of the cotton fibres, thereby creating an abraded effect that was uncannily like that of pumice stone.

During 1989, many laundries switched entirely to enzymes in place of stone. Gone was the perpetual noise of rattling stones. Gone, too, were the maintenance problems of damaged cages and bearings and troubles with effluent disposal.

The whole process was cleaner and a step forwards to a more environmentally friendly situation had been made.

There were some repercussions. The price of pumice stone plummeted, and certain barrel machines stood idle.

By the summer of 1990, fickle fashion changed again. Strongly abraded finishes were in demand, and the industry compromised by combining stones and enzymes and returning to barrel washers. This remains the most universally practised stonewash treatment.

At the start of 1986, hypochlorite bleach was often added from jugs or pails through front-loading hoppers. Crude, inaccurate and hazardous, it often caused bleach spots on garments.

Around 1991, peristaltic pumps became popular to feed liquid supplies to washers. They were considered to be more accurate and could be used in large automatic dosage systems. Wash programmes could be set on the microprocessor controls of the washer and when a particular chemical was required, a signal to the pumps via a chemical control would result in the correct amount being fed into the washer at the correct time.

By 1996, however, even this development had been superseded by systems that use flowmeters in place of peristaltic pumps. The microprocessor still operated a unit that signalled for supplies, but the chemical lines were under constant pressure by means of a small air-activated diaphragm pump, and each washer had a flowmeter through which each chemical was measured accurately. This system needs less maintenance than the peristaltic pump system, and is claimed to be more accurate.

On the subject of bleaching, it must be mentioned that the denim washing industry stands on the threshold of a major breakthrough which could have even greater repercussions on the trade than the introduction of cellulase enzymes.

There has been enormous pressure from local authorities and environmental protest groups to cease use of hypochlorite in bleach washes.

New products involving a laccase enzyme (a type of oxidoreductase) are able to bleach indigo dyed denim down to all levels including superbleach shades. Where a sulphur dyed bottom has been used in the indigo dyeing, the shades are more greyish in tone, which some customers actually prefer. There are no problems of fabric degradation.

The whole process is much more environmentally friendly and the extra costs are minimal.

Fibres impact on processes

With so many developments in new machinery, new chemicals and modifications to processing, it has been fortunate for laundries that the nature of new fabrics introduced during the decade has not been so challenging. Indeed, the only truly new fibre to have made a significant impact in denim fashion has been Tencel from Courtaulds.

Very distantly related to rayon, Tencel is a much stronger fibre with improved properties that can compliment the properties of 100% cotton, particularly in softness of handle. It can also be used in 100% form in the lighter type of chambray denim where the lush peach-skin handle is a particularly pleasing feature.

Laundries have had to learn “bio-polishing” techniques to develop the unique handle of Tencel, but such treatment can be done without the need of new machinery, or for different chemicals.

Mention of cellulase enzymes has already been made, but in this case their use is not for an abraded appearance but to remove unwanted fibrils from the fabric surface once the initial fibrillation process has been completed.

In conclusion, the years between 1986 and 1996 have been both worthwhile and full of interest. Denim washing has advanced from a rustic art to a controlled science, and ultimately the consumer has shared the benefits. Will the next decade be just as eventful and progressive?

One thing is certain. Denim will continue to be in demand and fashion will strive to create new washes and standards to challenge laundries.