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Singles: Housemaid\'s Hands - No Problem!

Dishwashers are worthwhile even in one-person households

Even if you live on your own, you don't need to be afraid of getting housemaid's hands: modern detergents and dishwashers destroy dangerous germs so effectively that singles can let used plates, cups and cutlery pile up for several days without any problem before they switch on the dishwasher.  These are the results of a detailed study carried out by the University of Bonn.

In small households there is often so little washing up that the use of a dishwasher does not seem to be worth it. People could, admittedly, allow the dirty dishes to pile up for a couple of days before switching on the dishwasher. Yet many people see that as unhygienic and are afraid that they will not get these piles of dirty dishes clean by using normal dishwasher programmes. Experts in the field of domestic appliances from the University of Bonn have now demonstrated that this worry is not justified. 'This means that the dishwasher's economic and ecological advantages compared with manual methods can also be used by singles,' says Professor Rainer Stamminger, who has been heading the investigation.

The study, which has just been published, was carried out by Dr. Sarah Ihne. She was able to show that the number of germs on the dishes is reduced by a factor of at least one hundred thousand while the dishwasher is running - and this is true even in unfavourable conditions such as low dishwasher temperature and short programmes. 'There is no risk involved in allowing the dishes to accumulate over several days,' Professor Stamminger stresses.

Hardly any detergent residues

In her PhD thesis Dr Sarah Ihne also investigated how much detergent is left on the dishes which have been washed. 'We were only able to detect extremely small residues,' she says. 'This is true both for dishwashers and for manual dishwashing.' However, if the dishes are not rinsed in clean water when the washing-up is done by hand, appreciably larger amounts of residues can be measured. Although these residues do not constitute a health risk, Professor Stamminger still recommends that the dishes should be rinsed in clear, cold water. The dishwashing process itself should take place in water which is as hot as possible using an amount of detergent which is not excessive, he adds. 'Washing the dishes under a running tap, however, is a waste of water,' he warns.

Dishwashers also remove residues of detergents and rinsing agents better the more water they use. Professor Stamminger therefore sees no reason to continue to improve the economical use of water by dishwashers. The Bonn team was able to demonstrate in previous studies that dishwashers, when properly used, wash a good bit more economically than people. In their standard programme modern dish-washers only use ten litres. Professor Stamminger comments: 'This is the absolute minimum, in fact it might be more than is desirable.'

Additional information on efficient and sustainable dishwashing is available at

Professor Rainer Stamminger
Institute of Agricultural Technology of the University of Bonn, Section of Household and Appliances Technology
Tel.: ++49-(0)228-735955
Fax: ++49-(0)228-732596
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