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15:
What is the acceptable percentage of water retained on terry towels
after extraction? What is the recommended drying time and
temperature?
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September
2002
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| Answer: The amount of water extraction
can vary, but an average washer extractor reduces retained moisture
by approximately 50 percent. Cotton terry towels will have a saturation
point of .3 gallons per pound, or approximately 2.5 pounds of water
per pound of cotton. Most often one refers to the retained water
as moisture retention when discussing extraction efficiency. An
example would be a 100 lb. load of clean dried cotton terry towels
which would hold approximately 30 gallons of water, or 250 pounds,
for a total of 350 pounds. Extraction reduces the retained water
by approximately 2 pounds of water per pound of cotton, leaving
50 pounds of water to be removed in the drying process. In general,
extraction is better when the last bath water is 110 degrees or
more, and a good fabric softener is utilized to lubricate the cotton
fibers.
There are a number of variables in regard to drying time for
cotton terry towels, depending on the equipment being used. Some
dryers have programmable inlet and outlet temperatures, whereas
others simply have adjustable outlet temperatures. In general,
dryers can be set for cotton at outlet temperatures of 180-210
degrees without worrying about scorch from temperatures that are
too high. The size of the load will also have an effect on drying
time. If one puts the correct poundage into the dryer and it is
operating correctly, one should be able to dry the cotton towels
in less than 30 minutes. Remember, a dryer should have good fresh
air to burn correctly, and the dryer lint filters should be kept
clean.
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Rich Fitzmorris is Vice President
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for more than 25 years and can be contacted directly via email at
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16:
Is there any effect of high water pH in a laundry wash process?
Our normal water supply pH is 7-8, but I recently encountered a
pH of 9. What might cause this? Is it safe to increase sour to maintain
a final linen pH of 6-7, or should I stick to the rule that final
pH should be one less than the water supply pH?
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September
2002
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| Answer: Before making any changes
I recommend verifying that the water has indeed changed. Check the
pH meter against a standard buffer, and have a chemical technician
look into this further.
Washing and bleaching steps are generally unaffected if the
incoming water pH is somewhat high. However, rinsing and sour
baths can be affected. When titrations of the wash formulas are
taken, be certain that total alkalinity is being reduced properly.
When using an alkaline base chemical system, the last rinse should
be titrated to less than 50 parts per million of active alkalinity.
The cause of higher than normal fresh water pH would be at the
source of the water. The local water treatment plant often has
to make adjustments if they switch from one source of water to
another. Perhaps the treatment plant is trying to control the
quality of the water by having a high pH during a time of prolonged
high temperature weather conditions. If you still have concerns
about the incoming fresh water quality, I suggest contacting the
local water utility service.
The pH of the incoming water generally has nothing to do with
what the final pH of the textiles you are washing should be. The
finishing pH is what is important for fabric quality and comfort.
There is no rule that says you should be only one pH scale less
than the water. It might be that you would not have any problem
depending upon what the textile is, however the pH of our skin
is approximately 5.5. Therefore, when items that are worn have
a significantly higher pH, they could become a possible irritant.
I recommend dropping the pH to the acceptable levels of the past,
and continue to investigate why the source of water has experienced
a change in pH.
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