|Simulating Hand Dishwash
Hand washing of fabrics is the most important method used in many parts of Latin America, Africa and Asia. Worldwide, over 9 million tons of laundry bars and pastes are used, mainly for this purpose. In an attempt to improve the performance of such products it was necessary to develop a method for the evaluation of products under hand washing conditions and the ASP evolved from this development.
This machine is developed by Savonnerie Anglaise Ltd. A generalised method of hand washing practiced by consumers in most countries consists first of applying the product to the wetted fabric placed on a hard surface. Then a brush is used to scrub the fabric. After this operation the fabric is usually soaked for at least an hour in the water containing the product and then the earlier operation is repeated. Finally the fabric is rinsed in clean water.Although this could be copied in a laboratory exercise, it was found to be very operator sensitive and very time consuming. It was therefore necessary to automate the process for evaluation purposes, to eliminate operator variability and improve reproducibility, and reduce operator time.
The ASP-machine was designed to simulate the hand washing method and uses a semi-stiff brush to pick up water from a container, pass across a laundry bar held at a fixed height, then brush over stain cloths.
This operation is then automatically repeated as many times as considered necessary. In practical operations it has been found that 50 machine cycles, followed by 1 hour soaking in the water in the container, and then a repeat 50 operations, still using the same water, gave good correlation with a laboratory hand washing method. The water temperature usually used is 20°C but this may be increased if thought necessary to reproduce conditions in warmer countries.
The machine can be used with any stain cloth, but best results are found using small Circular stains. Details of this method are contained in the operating manual supplied with each machine.
Although relatively little work has been carried out so far on other uses, the machine, in principle can be used for hard surface cleaning appraisal. This is achieved by replacing the stained cloths with a soiled hard surface.
Trials are also in hand to evaluate fabric hand dishwash products, by using a solution of the product in the water container at an appropriate concentration.
High Throughput Screening