Processing polyester table linen safely

Meeting customers’ expectations of a pristine stain-free, fault-free and well-finished result is not always easy when processing table linen.

Waiting or kitchen staff often use napkins, or even tablecloths, to wipe diners’ dishes, kitchen utensils or surfaces. Staining, especially from exotic spices, can be difficult to treat, as is linen that is left lying around before being sent to the laundry.

Table linen that is made from 100% polyester (including spun polyester) will last much longer than 100% cotton products and polyester also retains colour better. However, it has disadvantages that need to be taken into account in processing if its good looks are to last for its lifetime.

The wash process must be designed to suit the material. To avoid excessive creasing in the wash, polyester items will need to be loaded into the washer at a level that is 20 – 25% below the machine’s rated capacity. Polyester’s physical features mean that if it is loaded to the same level as 100% cotton goods, there is a high risk that the mechanical action will not be sufficient to remove soiling efficiently. So a higher percentage of work needs re-washing.

Too high a degree of loading can also lead to excessive pressure creasing and increase the risk of thermal-shock creases and of larger pieces suffering roping creases.

Polyester is naturally oleophilic (attracted to oily substances). Many of the edible oils and fats used in cooking are highly refined and will be difficult to remove without high levels of alkalinity and a raised wash temperature.

However, higher wash temperatures will often “set” protein stains, such as blood and many food stains and make them difficult or impossible to remove.

The wash process needs to cater for the range of soiling types often found on table linen. This will normally require a 5 – 7 minute wash with a medium dip at 35 ­– 39C to flush away loose particulate soiling as well as to soften and remove as much protein soiling as possible. This should include a good dose of low-alkali detergent (800 – 1,000ppm).

After draining, fill the washer to a medium-low dip level and use high amounts of alkali to achieve a concentration of 1,500 – 2,000ppm. Raise the wash temperature to 71C and run this main wash for 10 – 12 minutes. If possible, subject to requirements, add sodium percarbonate dosed at 5g/kg at this stage to help remove any stubborn and difficult protein soiling and vegetable dyes. Peracetic acid or hydrogen peroxide can be used as an alternative but sodium percarbonate will give a better result.

The wash process must not only remove soiling but also prevent removed soiling from re-depositing. The mechanical action in the wash will generate a strong static charge in the polyester and this charge can attract particulate soiling and non-emulsified oils and fats back onto the fabric.

To prevent this occurring, the process should include a non-ionic surfactant (ie, one that does not have any electrical charge). Polyester also needs a higher level of alkalinity than does 100% cotton. High alkalinity will ensure good emulsification of the oils and fats and prevent re-deposition.

A detergent formulation with an alkali builder that contains sodium metasilicate will have excellent soil suspension properties and also emulsify oils and fats efficiently.

Some detergent suppliers use low levels of metasilicate (to reduce their costs) and use the lower pH alkali, sodium carbonate, which has little or no suspending power. When using such formulations, it is essential to add a good soil-suspending agent, such as SCMC, at the right concentration.

Failure to use sufficient alkali and the correct surfactant will lead to premature greying of white-work and a gradual masking of colours.

A stack of white polyester table-linen with a “zebra” effect of varying shades of grey and white indicates that the processes need to be adjusted to prevent soil re-deposition. Piles of polycottons may also have a “zebra” effect for the same reason.

To avoid thermal shock creasing, a cooldown phase should be used at the end of the main-wash stage before the hot liquor is drained from the machine.

Most modern washers with a cooldown phase will have the cooldown cold water inlet fitted so that the water enters the machine at the bottom, well below the dip-level line.

This allows the washer’s water to cool gradually. The cooldown period can be programmed into the machine’s PLC.

Try to avoid using machinery that does not have such a cooldown function. Spraying cold water from the top of the machine directly onto the polyester fabric can cause localised and severe thermal shock creasing.

Finally, polyester will require reduced extract times or membrane pressure to avoid the risk of pressure creasing. Unlike cotton, polyester does not absorb moisture. The only water on the fabric will be held in between the fibres and weave.

Some launderers believe that a cooldown is unnecessary as the fabric will be fed through a multi-roll ironer at high temperature. They argue that this will effectively remove creases put into the fabric during the wash or while the work is stored until it can be ironed.

While the ironer will remove most readily visible surface creases, if the ironed table-linen is then viewed at an acute angle, break-marks will be readily visible as linear marks covering the whole surface. This is because polyester has the appearance of a “glass rod” at high magnification.

So as the fibres bend, ridges will form on the inside of the bend. Even when the polyester fibres straighten, the inside ridges remain and more ridges form on the opposite side as the “stretched” side now concertinas.

This leads to the “cracked-ice” appearance frequently seen when 100% polyester cloths are laid out over the table. The effect can be seen in both bright and subdued lighting.

To avoid problems, polyester linen must also be stored correctly while it is waiting to be ironed. To avoid pressure creasing on the pieces at the bottom of the pile, it must not be crammed too tightly into containers.

It must not be left lying around too long before being ironed, again, to avoid pressure creasing.

Polyester must always be covered during storage to avoid localised evaporation and dry areas on the linen at the top of the pile.

This is because the residual moisture on the polyester table-linen acts as a heat-sink when the item is fed through the ironer – thus keeping the polyester below its melting point.

However, in areas that do not have any residual moisture, the polyester fibres will be heated above their melting point. As a result the material will glaze leaving oily-looking patches over the cloth, where the polyester fibres have melted and flattened.

Finally, when ironing 100% polyester – never run the ironer so slowly that the polyester items are too hot to handle when they are discharged from the ironer. If polyester is overheated during finishing it will lead to overall glazing giving a very shiny finish and damaging the fibres.

To avoid this, reduce the steam pressure to lower the temperature of the ironer bed or increase the ironer speed.