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Washing-up liquids
placed into a plate rack to dry.
The end point of the test is when the
foam collapses. The number of plates that
have been washed by that time is
calculated and the plates are then visually
assessed to determine how many of them
are classed as being ‘greasefree’. This is
done visually, with reference to a set of
photographic standards numbered from 0
to 5, with 0 being the worst score. Tests are
always carried out in duplicate and the
results presented are the average of the two
tests. The temperature of the water at the
end of the test is also recorded and
reported.
The results are reported to the client in
a simple, easy to read format as illustrated
in table 1, in which three test products,
referenced A, B and C, have been
evaluated.
Table 1: Test results as reported to
the client
SATRA has developed a semi-automatic plate washing
test machine.
The evaluation of domestic cleaning
products would not be complete without
the appraisal of washing-up liquids used
for hand washing of domestic crockery,
cutlery and kitchen utensils. In order to test
these products, it is necessary to try to
simulate the consumer’s dish-washing
practices as closely as possible. To allow us
to do this at our cleaning technology
facility, SATRA has developed a semiautomatic plate washing machine, which is
used in conjunction with SATRA’s plate
washing test method.
The semi-automatic plate washing test
machine comprises a stainless steel basin,
a rotating mechanical drive which holds a
nylon brush, and a removable pump for
circulation of the water held in the basin. A
circular plate holder is used to hold the
soiled plates and an electronic device
controls the length of time for which the
rotating drive and the pump operate.
Cleaning ability
The most important factor for the consumer
is generally the ability of the washing-up
liquid to remove grease from the items to
be washed. The 'plates' have measured
amounts of lard which has been dyed blue
to assist the visual assessment of its
effective removal.
The plates used for this test are small
stackable saucers and are referred to as
‘mini plates’. These plates are washed in an
automatic dishwasher prior to use after
adding a standard dishwashing detergent to
ensure the removal of any residual soiling
from the plates, which might prevent the
staining materials from clinging to them.
Five litres of water are heated to a
temperature between 51ºC and 52ºC and
poured into the metal bowl. The washingup liquid is weighed in a weighing boat to
ensure that 0.6g is tested. This is then
added to the water. The water pump is
started and allowed to run for a preset time
in order to allow a head of foam to
develop. A soiled mini plate is then placed
in the plate holder and the plate washer is
operated, causing the brush to
automatically rotate 15 times against the
plate. When the brush stops rotating, the
mini plate is removed from the holder and
dipped twice into the water before being
Sample
A
B
C
Number
of plates
washed
Number
that are
grease free
19
15
6
6
3
4
In this example, product A has given the
best cleaning performance, having cleaned
19 plates before the foam collapsed, with
six of them being grease-free. Product C
has given the worst performance, cleaning
only six plates before the foam collapsed,
with four of them being grease-free.
Washing-up liquids cleaning 15 or more
plates are considered to have given a good
performance. Those cleaning less than ten
plates are classed as performing relatively
poorly, even when they produce a good
number of grease-free plates. In general,
the consumer will be looking for longlasting
suds as a sign of a good product.
How can SATRA help?
For further information on the testing of
washing-up liquids or other cleaning
products, please email
[email protected]