A five-star service for quality embroidered linen

Five-star hotels and restaurants often use embroidered linens to highlight their bespoke service. These look impressive provided their "as new" appearance can be maintained.
Embroidered work needs great skill and care in laundering to avoid problems with the decoration, such as a change of colour or fraying. Sometimes a line of holes or a tear can appear along the line of the embroidery itself and occasionally a "halo" can appear around the embroidery even though the thread is said to be colourfast.
Sometimes the problems will appear during the initial wash (pointing to a thread fault), but all too frequently problems do not appear for some time and then those concerned are puzzled as to what might be happening.
Why should embroidered items that have been washed many times suddenly display faults when nothing has changed? Even more puzzling is a situation where, in most cases, the threads seem to perform satisfactorily for many years in most cases but one or two customers repeatedly report colour changes.

Types of embroidery thread
In theory it is possible to embroider linens with a wide variety of threads and thread colours, made from different fibre types and using different dyeing techniques. In practice, most embroidery threads are made from one of two fibres, either viscose rayon or polyester.
Viscose rayon has a strong following with designers, who praise the wide range of colours and value the very high lustre that can be achieved with rayon and makes the threads look superb.
However, suppliers of viscose rayon are limited by the economic considerations of the dyeing techniques available. Most of these threads are dyed to be colourfast to washing but will not withstand bleaching with sodium hypochlorite.
There are random examples of rayon thread embroidery that does not have this problem. These threads have been vat dyed and can resist sodium hypochlorite but most manufacturers find this technique is not economic. This is because the quantities are too small to justify it when a manufacturer may offer as many as 300 shades and when price competition in the market is intense.
Polyester embroidery thread coloured by disperse dyeing has good resistance to sodium hypochlorite at the concentration and temperatures used in contract laundering and textile rental. As a consequence, the high volume contract market is presently dominated by polyester threads, with high lustre viscose rayon used only where
bleach-free washing can be assured.

The embroidery process
The embroidery process is highly skilled and uses dedicated equipment to produce bespoke results. The linen to be embroidered is mounted on a multi-head embroidering machine, the fabric is tensioned correctly and a backing material is used to stabilise the design so even quite complicated patterns can be produced economically.
If the item to be embroidered is single thickness and the decoration will only show on one side, the increase in fabric weight in the embroidered area is quite modest, depending only on the stitch density specified. However, if the piece involves a double thickness, such as a pillowcase edging, with embroidery appearing on both sides, then in this area there will be two thicknesses of embroidery thread and two layers of backing material in addition to the two layers of pillowcase fabric, so it will hold a lot of water.
Pillowcases acquire stains in use and the quality of establishment that specifies and is prepared to pay for embroidered cases will require any staining to be removed completely. The staining tends to be a mixture of protein and vegetable dye from food and drink or proteins from the user's skin and hair.
The proteins are supposed to be softened in a low-temperature pre-wash so that they can be completely removed with good detergency and mechanical action in the high-temperature main wash. The vegetable dye stains are then decoloured very easily with a little sodium hypochlorite in the rinse zone of the tunnel washer or in a bleach rinse in a washer-extractor.
The economics of modern laundering make it essential for high volume work to be processed in a tunnel washer. In these conditions it is very difficult to keep the sodium hypochlorite from permeating to every batch, even though it might be dosed into only half of the classifications being processed.
It is much easier to keep the items free of this bleach in a washer-extractor and so the standard advice for high volume embroidery is to use high quality polyester thread, because bleaching and colour change in the wash is not normally a problem with this yarn.
Where problems can and do occur is in the rinsing. It is essential to remove every trace of alkali from the textiles by thorough rinsing and/or neutralisation. If fabric that is otherwise perfectly rinsed carries chemical residues in the multi-layer embroidery, the concentration of these residues will increase as the moisture evaporates so eventually the residues cause problems during ironing.
Alkali residues give rise to yellow brown discolouration around the embroidery, creating a "halo" effect. This is caused by the action of heat from the ironer bed on the concentrated alkali, which then migrates from the embroidery.
If the residues include sodium hypochlorite, then the combination of heat and the concentrated chemical results in a chemical attack on one or more of the components of the polyester dye recipe. Even the use of disperse dyes cannot prevent the damage caused by the combination of heat and sodium hypochlorite.
If the chemistry damages all the dye components the colour will probably fade overall, but if one component suffers more damage than the others, the colour can change, for example from bronze to green, which is much more noticeable than a simple fade.

Wash processes for embroidery
How then can embroidered goods be washed in a tunnel washer with success every time and with no fade or change in hue? The first requirement is that the thread is bleach resistant and this can be gauged from the shade card, where the best suppliers indicate with wash care symbols the processes that the thread has been designed to withstand.
If the classification is to be
de-stained in the most economical way (which is normally by using sodium hypochlorite) then the dosage should be restricted to 3ml of concentrated bleach as delivered per kg of dry textiles.
Any stains that remain after being bleached at this dosage, are likely to be protein stains or a mixture of protein with vegetable dyes - in this case the protein prevents the bleach from treating the vegetable dyes.
This is a common problem on modern tunnel washer systems, if the pre-wash is much above 38C, because the higher temperatures can set the proteins rather than softening them. Much higher bleach dosages are then needed to burn off the protein stains and it is more difficult to rinse the bleach out of the embroidery.
High pre-wash temperatures are often associated with the heat that is recovered from either the hot effluent or from the boiler flue and reused in the fresh cold rinse water coming into the tunnel. If this results in poor softening of protein stains in the
pre-wash and if the problem is cured by increased alkalinity in the main wash, then the alkalinity going into the rinse zone will be much higher and the risk of yellow brown "halos" around the embroidery is much greater.
In some parts of the country, the raw water has high levels of alkali so that it is more difficult to rinse even single-layer fabrics efficiently.
In such areas it makes sense the neutralise the alkali in the rinse water by adding an acid sour into the final rinse. The best acid sours, such as sodium metabisulphite, are capable of neutralising not only the excess alkali but also any residual sodium hypochlorite bleach. These chemical neutralisation reactions are both faster than rinsing for reducing the level of alkali and hypochlorite to safe levels, but they still take time. The batch washer stage time must be long enough to allow the reaction to complete or even this technique will not work.
On some designs of tunnel washer it is possible to bring the bleach injection point forward by one stage, to create one complete extra rinse pocket after bleaching. This is a very good solution and much better than attempting to bleach in the pre-wash. Carryover of bleach from the pre-wash into the main wash on these systems is a major source of chemical damage and reduced textile life overall. It can also result in holes and tears along the embroidery if this decoration still contains bleach residues when it reaches the ironer.

GALLING, NOT BLEEDING: The residual alkali in this embroidered motif gave rise to a ring of yellow-brown galling around the logo, leading to the mistaken impression that there had been a colour bleed