Both laundries and kitchens can be hot, steamy places to work in and both need to make sure that the “recipes” used produce the right results for their customers. For the laundry, the recipe means the correct level of detergent combined with the right wash process.
Linen sent in from hotel and restaurant kitchens may be soiled with cooking oils, grease, food splashes and debris and have exceptionally heavy levels of soiling, which may present a problem for many laundries.
The range of kitchen-soiled classifications includes chefs’ apparel – jackets, trousers, aprons and sometimes hats; and kitchen cloths (known as rubbers) glass cloths and oven cloths. However, the catering sector may also send in other items, such as napkins and table linen, that have similar soiling.
All these classifications need treating differently from more lightly-soiled linen such as sheets, pillow slips and towels.
The first consideration when processing kitchen soiled work is to look at the type of soiling.
Hotels and restaurants may allow employees to use otherwise lightly-soiled items to wipe the excess food debris and left-overs off diners’ plate and such items may be sodden when they arrive in the laundry.
The soiling will be a general mixture of food containing protein and vegetable matter, beverages and high levels of highly refined edible oils and fats – each of which need to be processed differently if you are to get the best results.
Much of the food debris is water soluble or at least can be softened in cool water, making it easier to remove the soiling later. However, if the food debris is subjected to temperatures exceeding 39C, this type of soiling will be effectively “cooked’’ and be difficult, if not impossible, to remove, especially if it has a high protein content.
So the first part of any wash process for heavily kitchen- or food- soiled articles is a clear cold water rinse with a high dip. Letting the load move around in the washer with a high cold-water dip for 4 – 5minutes will often remove up to 75% of the soiling, making the rest of the cleaning process (and use of chemicals) more economical.
Some launderers claim to achieve even better results during this first “breakwash” stage by adding some straight detergent (but not alkali or built detergents).
However most detergents in common use today are fully or partially built with alkalis – and the inclusion of alkalis at this stage can have a negative effect on some soil removal, especially if there are high levels of blood-soiling present.
The next factor that will have a great impact on the ability to get these heavily-soiled textiles clean is the machine “degree of loading” (or DoL). This is the dry weight in grams of textile loaded into the washing machine per litre of the cage capacity. The common degree of loading used for large or small washer-extractors or rotary washers is 100g/litre. So a washer with a total capacity of 2,000litres it will be commonly loaded with 2,000 x 100g = 200kg.
However, the four requirements in any wash process are: time, temperature, detergency and mechanical action (often shown as a pie-chart known as Sinner’s circle) and the loading will have a big impact on the mechanical action.
The higher the degree of loading, the lower the mechanical action and the poorer the soil removal will be.
The effect of reduced mechanical action on soil removal is often difficult to see if the level of soiling is very low. But, for more heavily-soiled classifications, the amount of soiling removed (cleanliness) will be dictated by size of the machine load and the amount of mechanical action during the wash process.
Compare two washing machines: one 90cm diameter and 100cm deep and the other 60cm diameter and 224cm deep. Both have a cage of around 635litre and in theory, both could take a 63kg load. In practice the larger diameter machine will give the better mechanical action because there is a much better “lift and drop and squeeze” action.
Therefore, If the laundry wants to get this heavily-soiled work clean, it must use the correct degree of loading and this should be varied to suit the size and shape of the machine.
As a guide, based on 100% cottons with medium soiling, washing machines with a cage diameter of less than 100cm have an ideal degree of loading of 56g/litre. For machines with a cage diameter of between 100 – 200cm, the degree of loading is 72g/litre and for washing machines with a cage diameter greater than 200cm a degree of loading of 100g/litre is acceptable.
For launderers working in imperial measurements, these equate to 3.5lb/ft3; 4.5lb/ft3 and 5.5lb/ft3.
However, if the restaurant textiles you are processing are heavily soiled, the degree of loading should be down-rated by at least 15%.
After completing the breakwash rinse, the next step is to try to remove the more ingrained and stubborn food soiling. This will require a medium dip, the addition of a normal fully-built detergent and a wash temperature of 60C for 7 – 8minutes.
Some detergent suppliers will make specific dosage recommendations, normally expressed as grams of detergent per kilogram dry weight of work loaded. However these recommendations are made with costs in mind so the dosage is likely to be cut to a minimum.
If you stick to these minimum levels for heavily-soiled linen, it is likely that most of your processed work will start to take on various shades of grey. This work is often heavily saturated with high levels of refined edible oils and fats, which only start to emulsify at lower wash temperatures. The small amount of fat that is emulsified at these lower temperatures will very quickly use up the detergent’s suspending power.
As this fat is emulsified, all the particulate soiling removed during the initial part of the wash process will be released from suspension and redeposit onto the fabric. Once this has occurred it is almost impossible to remove.
The secret here is to ensure that there is sufficient detergent in this wash stage to achieve a light consistent lather throughout the entire stage. This can be done by continuing to add detergent to achieve the lather. Alternatively, and more cost effectively, add your normal detergent dosage but then add an alkali booster (preferably sodium metasilicate as this has excellent suspending power in its own right).
Once this stage has been completed, it is time to remove the last of the grease, fats and oils. This can only normally be achieved at higher wash temperatures and with high levels of alkalinity. A wash with a low dip at 75 – 80C with very high alkalinity for 7 – 10minutes will work extremely well here.
At the end of this wash stage, the rinsing can start, but even with such a well-developed wash process there is likely still to be some unremoved vegetable dye staining from old dried tea, coffee and wine. This can only be decoloured by bleaching.
If you have washed out the oil and protein staining properly, minimal levels of bleach are required. Add sufficient water for the first rinse to ensure the load is cooled to a maximum of 60C before adding sodium hypochlorite bleach. This should be dosed at 1g of available chlorine per kg dry weight of the load and the rinse should then run for 5 minutes. A standard high-rinse dip should be sufficient to cool the load to below the target 60C – but ensure this is achieved before adding the bleach to minimise the risk of increased fabric damage.
Continue rinsing as normal (another two rinses) before unloading. If the machine has an interspin then just two rinses in total are often sufficient.
If you do use the interspin, never use it between the breakwash, first and second washes. The amount of soiling still remaining on the load is often so great at these stages that an interspin will get the soiling embedded into the interstices of the material, making it even more difficult to remove.
At the end of this process you should have bright, clean and fresh-smelling kitchen work.
