Material solutions

Meeting the challenge of towel processing

1 July 2010



Ian Harris explains the laundry procedures that will ensure quality results every time


Towels are possibly the most intimate and hygiene-sensitive textiles that the launderer will ever encounter. They routinely come into contact with all parts of the body and therefore deserve special attention and care during handling processing in the laundry.

A towel is one of the few items that demands to be either chemically and/or thermally disinfected each time it comes into the laundry.

It is also one of the few items that is routinely abused by both hotel staff and by the guests. Staff may use the towels to wipe dry ceramics when cleaning the bathroom. This is not a big problem unless the ceramics have been cleaned with an acid descaler or with any products that contain bleach. Prolonged contact with such products, more than 24hours, is sufficient to cause either severe weakening of the cotton used in the construction of the towel or to rot the cotton away, producing large holes.

Hotel guests have been known to use towels to clean their shoes or to wipe off make-up directly onto the towel – something they are unlikely to do with their own personal towelling at home!

The launderer must therefore ensure that the towel is always disinfected. Severely soiled towels demand special processing conditions to clean them successfully without causing more damage than necessary.

Water hardness

Water hardness also plays a part in destroying the cleaning process. While the launderer may well be using softened water to ensure the optimum use of cleaning chemicals during the wash process, few of the launderers’ customers will be using softened water.

If the hotel guest or hospital patient uses unsoftened water to wash, the water that gets onto the towel when they dry themselves, will eventually evaporate leaving behind large quantities of hardness salts. These will destroy the soap or detergent during the wash process leaving the launderer with towels that become progressively greyer and harder with every wash.

All these factors mean that launderers face challenges if they are to produce hygienically clean towels that look as bright and white as the sheets. Towel processing problems start when the towel is purchased and enters the laundry for the first time.

When manufacturers produce terry towels on the weaving loom, the yarns used to form the loop need to have a fair amount of lubricant on them.

As the weft yarns are fed across the loom pointers will force the yarn in between the warp yarns to form the loop and the lubricant is added to reduce the risk of the yarn breaking.

The type and quantity of lubricant used will vary somewhat from supplier to supplier but generally the lubricant will be oil based and this in turn imparts a slippery surface to the towel which our senses interpret as feeling “soft”. This lubricant often makes the fabric less absorbent but more importantly the oils, fats and greases attract hardness salts from water.

These form a protective shell or coating over the oils and fats, As a result both the oils and fats and the salts will be difficult to remove and the towel quickly turns grey.

It is essential all new towelling is washed before being issued to the user and that the wash process should use significant amounts of additional chemicals.

On several occasions, I have tested new towelling directly from the manufacturers and have added more than three times the normal recommended detergent dose to obtain a bead of lather during the main wash stage.

Failure to ensure that new towels are correctly washed the first time will make it significantly more difficult to maintain a bright white towel with subsequent washes, especially if the laundry serves customers in areas where the water is very hard.

Customers want “soft” towels but removing the lubricant used during manufacture will make the towel feel “harsher”. Therefore some launderers like to add fabric conditioner on the final rinse to impart a “softer” feel. If the laundry does decide to use fabric conditioner, it should avoid adding too much to the final rinse otherwise the towel will be unable to absorb any moisture. The fabric conditioner effectively coats the fibres with a cationic waterproofing agent that reduces a towel’s drying ability.

It’s also worth noting that as many fabric conditioners are cationic, they will effectively neutralise the effect of the non-ionic and anionic soaps and detergents used in the wash process. If fabric conditioners are used then further detergent additions are often required when the towels are returned to the laundry for washing.

Tumble drying the towels correctly will often help to achieve the desired softness so that fabric conditioners are not needed.

However, tumble drying can have a negative effect on “softness” under the following circumstances.

• When the towels contain too much moisture from the washroom: The target moisture retention should be not greater than 50% and ideally it should be at or below 45%.

• If they are washed in hard water – greater than 72ppm (5degreesClarke) as measured in calcium carbonate; or

• If they are tumbled dry for too long or at too high a temperature.

This last factor will also reduce the fabric life as the greatest amount of damage to a towel occurs during the tumble drying stages and gets worse the longer and hotter they are tumbled.

Let’s assume that the new towel is correctly washed in the first instance and that the lubricants have been removed. The towel is now in circulation and being sent back regularly for laundering.

Hardness salts

When the towel is sent for washing it will be heavily laden with hardness salts and these must be removed effectively before they the main wash process begins.

To check the level of hardness in the towels, first test the washroom water supply to ensure it is soft (below 72ppm). Load the washing machine with towels and add a normal wash dip (without any detergent or other additives).

Run the machine for 5minutes and then, as the machine is drained catch a sample of the water, test again for the hardness – and be prepared for a surprise.

The options are therefore to either give all towels a cold water rinse before starting the wash process or to increase the detergent dosage on the first stage of the wash process. This will destroy the water hardness salts so that the detergent can effectively remove the skin oils and fats as well as the other soiling during the main wash stage.

It is during the main-wash stage that the minimum wash temperature of 71C for 3minutes plus machine mixing time must be achieved to ensure a reasonable level of disinfection. Launderers in the UK should remember that thermal disinfection temperatures recommended there are significantly lower than in the rest of Europe. So a process that fails to achieve even minimal thermal disinfection is unsatisfactory unless chemical disinfection is also used.

Finally launderers should check their rinse processes. Towels are designed to absorb moisture and at the same time they will absorb any chemicals dissolved in the water. It is essential that towels are correctly rinsed as any residual detergent or alkali can very quickly lead to complaints of skin irritation and rashes as well as turning the towels yellow, especially if they are over-dried in the tumblers.

A good method of checking that good rinsing procedures are consistently achieved is to use a dropper bottle containing phenolphthalein and place one or two drops onto a washed towel every few loads.

If there is no change in colour (phenolphthalein is a colourless liquid) rinsing has been completed correctly but if it turns magenta, then there is a problem.

However, residual alkali and detergent is not the only problem.

Increasingly, many launderers are using chemical neutralisation of the residual wash alkalinity to reduce the amount of water used during the wash process.

This involves using a sour or acid during the final rinse. Overdosing with sour can leave the towel with a strongly acid pH, which can cause skin irritation and also reduce the fabric life as cotton doesn’t like acids.

So the next time you are in a hotel, pick up the towel, bury your nose into it and breathe in deeply through your nose. If there’s the slightest rancid or sweaty residual odour, you will be using a towel that has the residue of the past 10-15 users on it.




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