We welcome Steve Anderton for the first in a series of guest blog posts from LTC Worldwide - the UK's leading textile care specialists, regularly seen in the press. LTC offer a wide range of consultancy, training & testing services for the textile services and laundry industry, and provide independent expert services to both Government and private institutions. Based in the UK, they work globally, particularly in Europe, North America and the Middle East.
Steve is taking a look at 5 of the toughest stains laundries have to deal with, and giving advice on how to remove them - even if you don't yet use the Hydrofinity system.
How to Remove the Top 5 Toughest Stains
If you get a regular visit from your detergent supplier, it pays to get them to do a stained rewash analysis each time they come, so that you can get a clear picture of what stains are not coming away - and do something about it. The ones which feature in most lists as recurrent problems, both for washer extractors and for tunnel washers, are:
Old bloodstains with a brown rim on sheets and towels
Animal fats and fish oils on polycotton and 100% polyester table linen
Faint blotchy yellow-brown marks which appear on bedlinen and towels during the wash
Red or brown marks from sauces on table linen
Black metal marks on kitchen cloths, and sometimes on table napkins
There is a sixth major problem on certain sites – discrete pairs of black dots, several mm apart, which are termed ‘snakebite’ marks, because of their appearance - but these are massive problems only on a small number of sites. These arise from seal breakdown on tunnel washers and there is currently only one successful method for recovery of the stained linen (based on the Hydrofinity process).
1. Removal of old bloodstains
Blood contains fatty proteins which must be softened in a cool pre-wash (38C is ideal, but certainly below 40C), so that they come away completely in the main wash. This requires good detergency, vigorous mechanical action and five to ten minutes at main wash temperature. If this is done correctly every time, then all the blood will be removed and there will be no old bloodstain to fret about. The Hydrofinity machine design is particularly effective with the softened fatty proteins in blood, because the polymer XOrbs™ will automatically attract them and aid removal.
If the pre-wash is too warm, even by a few degrees, the fatty proteins will be ‘set’ onto the textile and be extremely difficult to remove (ed - not a problem in the Hydrofinity machine, which operates at lower temperatures). Tackling the residual stain with excessive bleach is the wrong solution, because bleach is not very effective on set blood and it will damage the cotton in the textile. It is better to use a rewash process with high alkalinity (using sodium metasilicate for example, or sodium hydroxide in a Hydrofinity machine) in a single main wash stage, which will saponify and solubilise the blood proteins and get them away. The textiles then need three good rinses to remove the residual alkali.
If, despite your best efforts, there is a brown ring left on the textile round the edge of the bloodstain, this requires a different solution. The ring is staining of the fabric with iron oxide, made by chemical reaction between the haemoglobin in the blood and the oxygen in the air in the guest room or in the wash water in the laundry. This is not a washable stain. Iron stained fabrics should be accumulated for a single chemical treatment using oxalic acid crystals.
Use a single wash process in a washer extractor, dosed with 20g oxalic acid crystals per kg of dry textile. Do not add any detergent. Run the stage for 10 minutes at 60C. The iron oxide will be converted to iron oxalate, which is soluble and will go to drain at the end of the stage, leaving the fabric stain-free. The load then needs three good rinses to remove any acid residues.
2. Removal of animal fats and fish oils from polycotton & 100% polyester table linen
The problem with animal fats and fish oils is the very strong attraction between fats or oils and the polyester fibres in the cloth. Washing with normal detergent dosage will not overcome this attraction and increasing the detergent sufficiently to achieve this can be very expensive.
A better solution for a washer extractor is to dose the pre-wash with an emulsifier designed for animal fats and fish oils (ask for one with an HLB (hydrophilic-lipophilic balance) ratio in the range 9 to 13). The Hydrofinity machine should need only a minimal dosage of emulsifier, because the polymer XOrbs™ in this machine will already have a substantial attraction for the animal fats/fish oils.
Although the chemicals supplier will be able to give some advice on dosage, trial and error may be needed to meet customer requirements at minimum cost, especially for food industry workwear with substantial contamination.
3. Faint blotchy yellow-brown marks which appear on bedlinen and towels during the wash
Faint yellow or yellow-brown marks, which become visible, after washing, on previously unstained textiles, can be infuriating. Rewashing with bleach can either have no effect or make them worse.
This type of mark is becoming increasingly common and it arises from the increasing use of chlorhexidine disinfectant in proprietary skin treatments such as Savlon ointment, protective sun creams, artificial tans and a wide variety of other retail skin products. The NHS uses hibitane soaps and gels which derive their effectiveness from chlorhexidine.
The staining is a consequence of the chemical reaction between chlorhexidine and either free chlorine or the chloride ion in sodium hypochlorite bleach. The reaction produces an indelible yellow or yellow-brown dye, which colours cotton fibres effectively and permanently. The problem can be avoided in laundries processing healthcare linen by bleaching only with hydrogen peroxide, which gives no stain formation. The increasing occurrence of chlorhexidine staining in hospitality textiles could require the same solution.
The real problem is that once the staining becomes visible it is too late to do anything about it. There is no known recovery process.
Some laundries are ceasing the use of sodium hypochlorite bleaching on the normal wash and using hydrogen peroxide for the stained rewash, but this is wasteful of the time and effort to sort the rewash and re-process it.
Others use hydrogen peroxide on the normal wash and stand the extra cost. This works best, at minimum cost, if protein stains are removed by first softening in a low temperature pre-wash (below 40C), so that there is no reliance on hydrogen peroxide for protein stains (because it is not very effective on these – it is designed for vegetable dye stains and medications based on these).
4. Red or brown marks from sauces on table linen
Bleaching is a chemical oxidation process which is very effective at removing vegetable dye stains from blackcurrant, beetroot, tomato, beer and similar natural plant-based sources. However, it only works if the bleach can get at the vegetable dye. If the colouring is masked by oily, fatty proteins from meat juices or nut oils, then bleaching only works if these are effectively removed first.
The same comments as in the previous paragraph apply and if protein stains are removed by softening in the low temperature pre-wash, so that they come away easily with mechanical action and detergency in the main wash, then very little bleaching power is needed, even with very heavy staining.
The side benefit of this is a significant reduction in chemical damage to the textile and consequent increases in textile life. This is why the best laundries need to inject only half as many new items into circulating rental stocks as the poorest ones.
5. Black metal marks on kitchen cloths and table napkins
Black metal marking on kitchen textiles and table napkins used to be caused by iron staining and could be removed using the process given earlier for the iron oxide ring around old bloodstains. Nowadays, the widespread use of aluminium in the kitchen has given rise to aluminium marking, which is more difficult to reduce.
The best results are obtained by a single hot wash using a strongly alkaline detergent at the ‘heavy soiling’ dosage, augmented by a strong dose of an alkali booster, such as sodium metasilicate crystals (sodium hydroxide in a Hydrofinity machine) at a typical loading of 20g per kg dry textiles. The hotter and longer the better, but it is worth trying 60C for 15 minutes as a starting point.
The aluminium metal particles embedded in the surface of the textile are converted into aluminium hydroxide which is sufficiently soluble to be carried off to drain with the wash liquor. Finish the process with three good rinses to remove any residual traces of alkali.
General principles for getting textiles stain-free first time
Laundering is not rocket science and does not require a chemistry degree! The most successful launderers are those who follow basic craft principles.
The first and most important is to understand the need to soften protein stains in the pre-wash by using a small detergent dose (about one third of the total detergent needed should go into the pre-wash, leaving two thirds for the main wash). This only works if the pre-wash temperature is held below the setting point of any proteins present in the staining.
For example, the proteins in egg white and many other foodstuffs start to set and change from colourless to white above 40C, which is why keeping below this temperature is so critical. Watch an egg frying in the pan for a superb visual example of this and note how difficult it is to wash a pan with hardened egg-white securely cooked onto it! This is such a simple precaution but one which is widely missed, even on the latest high-volume tunnel washing lines.
If a textile contains polyester, then a wash process which works for cotton is unlikely to be as effective. This is because polyester is oleophilic – it has a very strong attraction for any fat or oil. You will need significant extra detergency or an emulsifier with the correct HLB value to solve the problem and produce stain-free work.
The only wash process which addresses this from the machine design point of view is the Hydrofinity system, which uses polymer XOrbs with a unique attraction for fats and oils. When this is coupled with the much higher chemical concentrations achievable because of the low water requirement, the advantages of this design for oil stain control becomes understandable.
The best systems produce work which is 97% stain-free. Textiles which are still stained after the normal wash should be sorted from the system and classified for further recovery using one of the processes described earlier. These will increase the stain-free yield to over 99%, economically and consistently.