How moisture works in drycleaning
Part 2
As explained in Part 1 of this series, we
learned that water added to drycleaning solvent with no
detergent present will float on the surface of
perchloroethylene, and it will settle to the bottom of
hydrocarbon or Stoddard (petroleum-based).
This is the result of the weight of water
being lighter than perchloroethylene solvent and heavier than
hydrocarbon and Stoddard solvents. Fabrics comprised of natural
fibers that are placed in the solvent/water mixture will absorb
the water, and become wet, if sufficient water is present.
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This action makes the
solvent/detergent/water all dissolved within each other
provided the amount of detergent is sufficient to carry the
amount of water added.
This condition is the
“micelle” formation, which was discussed in my
article on drycleaning detergents.
Briefly, if a load of fabrics is being
cleaned and water is manually added, the fabrics would not
absorb all the added water if the solvent is adequately charged
with drycleaning anionic detergent. The micelles of solvent and
detergent act as a storehouse and hold some of the added
moisture.
The water picked up by the fabrics and
the water remaining as part of the solvent/detergent/water
system (micelles) act together to remove water-soluble soil and
stains from the fabrics.
The higher the amount of charge detergent
the more moisture the solvent micelle formation can absorb with
less increase in solvent relative humidity (SRH).
You can prove this fact by pouring some
solvent into a small glass container, adding anionic detergent
about one-fourth the height of the solvent level, then adding a
small amount of tap water and stirring the three liquids
together.
After they settle, you should notice only
the tan color of the detergent and solvent solution, and the
water should not even be visible.
If the solution appears a little milky,
then add a little detergent until the solution becomes clear.
You can then add some more small amounts of water and stir the
mixture. If the solution then appears milky, you can add more
detergent and stir until the solution is again clear with a tan
color.
The anionic charge works well with tap
water. However, I recommend using a stock solution of one part
spray spotter detergent to ten parts tap water when adding
moisture manually. This spray spotter detergent gives
additional fabric penetration and disbursement to the moisture.
An important fact to remember is that
most fabrics will already have adsorbed some moisture from the
humid air in your plant before they are placed into the
cleaning machine.
Therefore, the use of an anionic
detergent in the proper proportion is critical to safety as
well as quality drycleaning. Remember as stated in part 1, a
1.5 percent to 1.7 percent anionic charge is recommended for
better results and complete safety.
Solvent flow rate has a great influence
on removal of water-soluble soil. In a charge system of anionic
detergent, we want to condition the solvent with moisture
(micelles), and then we want the moisture to dissolve
water-soluble stains and soil.
Having the proper solvent relative
humidity does not necessarily guarantee that the garments in
the load will pick-up the water rapidly enough to give high
water-soluble soil removal (WSSR).
The one controlling factor of the speed
with which the moisture is added and pumped into the washer is
the filtered solvent flow rate. Since the load immediately
begins to remove water from the charged solvent, we need a
solvent flow rate close to one change per minute per pound of
load (3Ž4 change per minute at a minimum) since it takes a
faster flow rate to return the moisture content to the level
where the fabrics can pick up more moisture.
This is very critical when using a
conductivity control which constantly reads the amount of
moisture contained in the solvent-detergent solution by means
of electrical conductance and adds water automatically if
needed.
When adding the water stock solution to
the button trap, or injecting it directly into the cylinder
(which is recommended), it should be done after about two
minutes of filter circulation so the moisture in the fabrics
can be imparted to the solvent for conditioning before the
addition is made.
On high humidity days, manual additions
of water should be reduced, and on low humidity days it should
be increased.
On regular hard finish loads, about
one-half ounce to two-thirds ounce of water stock solution per
pound of garments should be added to the button trap or
injected directly into the cylinder (after about two minutes
after the solvent level has been reached) on low to normal
humidity conditions (60 percent to 75 percent).
On high humidity days (over 75 percent),
the amount of moisture stock solution added or injected should
vary between one-third ounce to less than one-fourth ounce, or
even nothing, per pound of garments cleaned.
On very high humidity days (raining hard)
you may consider pre-drying the load for about five minutes and
then adding up to one-third ounce of moisture stock solution to
the wash.
On soft finish and knit garments, no
moisture should be added or injected on high humidity days, and
only one tenth of an ounce of water stock solution should be
added or injected on low humidity days.
A conductivity control will not add any
moisture on high humidity days unless the load has been
pre-dried since the garments will be pre-conditioned by the
environment within the plant.
The simplest way to measure your cleaning
area’s relative humidity is by a hygrometer mounted on
the wall. These devices are inexpensive and can usually be
purchased at a department store or a marine supply store.
Remember that the presence of a little
moisture will reduce the generation of static electricity and
lint on the garments.
Regarding the use of spray spotter
detergent in the water stock solution, these detergents,
although formulated in a water base, are both solvent-soluble
and water-soluble. Therefore, they make excellent water
disbursing agents in drycleaning solvents, and they assist the
water in quickly dissolving water-soluble soil.
Mixing one part spray spotter detergent
to ten parts tap water and stirring is both economical and
highly effective. Your field technician will usually install
the injection device upon request at no charge as long as you
continue to use his/her products.
Solvent temperature has a lot to do with
water-soluble soil removal. Cold solvent (below 65°F) will
reduce water-soluble soil removal way below that obtained at
75°F to 80°F, all other conditions being the same.
Increasing the solvent temperature above
85°F will not only fail to increase water-soluble soil
removal but it will also make control of solvent relative
humidity much more difficult. The same moisture added to
solvent at a temperature in excess of 100°F will almost
double that of solvent at a temperature of 75°F to
80°F.
It is a known fact that the effect of
high temperature on solvent relative humidity is the reason for
shrinkage or pilling of soft wool and wool gabardine, not the
excessive heat alone (with no moisture increase).
Loading your drycleaning machine
properly, not over loading, has a great impact on water-soluble
soil removal.
With loads that have the same original
moisture content, a drycleaning washer-extractor or
dry-to-drycleaning machine loaded at about 2 1Ž2 pounds per
cubic foot of cylinder volume will remove as much water-soluble
soil in 15 minutes as a load of four pounds of garments per
cubic foot of cylinder volume in 25 minutes.
Plants with a high cleaning volume can
achieve good results up to three pounds of garments loaded per
cubic foot of cylinder volume.
The use of a charge system with moisture
additions is not recommended for machines using adsorption
filter cartridges or tonsil powder pre-coats as mentioned in
Part 1.
Only using a cationic detergent
containing moisture as a catalyst could be practical since the
detergent and moisture would be worked onto the surface of the
garments during the “batch” run (by-passing the
filter).
Therefore, since the batch run is only
for three minutes to four minutes, and the detergent and
moisture mixture is substantive to the garments, only a very
small amount of detergent and moisture (one-tenth ounce per
pound of garments to one-fifth ounce per pound of garments)
would be applied for water-soluble soil removal.
Most of the wash being without any
detergent and moisture during the ten-minute filter run is not
enough detergent, moisture or time for satisfactory
water-soluble soil removal.
When using the cationic injection system
with formulated small amounts of water, it is injected into the
cylinder inlet line after the load has been wet with solvent.
The small quantity of this mixture is employed since it is an
emulsion and not a micelle formation.
As an emulsion, the water acts on the
surface of the fabric to dissolve and sweep away the
water-soluble soil, very much similar to a spotter pre-spotting
with a water-detergent-solvent mixture using a brush or
spatula.
This method of cleaning requires a
solvent flow rate a little slower than one gallon of solvent
per pound of garments per minute in order to allow more time
for the moisture to do its job in the wash cylinder.
A distillation rate of at least 20
gallons of solvent per 100 pounds of cleaning is recommended on
the cationic detergent system. Too much non-volatile residue in
the solvent is a deterrent to the effective use of the cationic
detergent.
Sugar and salt removed from garments in
the cleaning washer are dissolved into the charged solvent
(anionic detergent) and cannot be removed from the solvent by
non-adsorptive filtration, nor can they be removed by running
successive dry loads.
The salt and sugar are dissolved in the
detergent and build up to the point where it will lower its
ability to dissolve more salt and sugar. Distillation, running
the solvent through adsorption cartridges (activated carbon and
activated clay) or through spin disc filters pre-coated with a
mixture of tonsil powder and diatomaceous earth are the only
ways to remove the salt and sugar.
In the “old days,” we would
run a load of dampened cotton rags for about ten minutes and
followed with a load of clean, pre-dried cotton rags.
Sugar build-up can cause brown spots to
appear on light-colored garments. A garment cleaned with a damp
spot on it will pick up sugar if the solvent is nearly
saturated with sugar. Then drying at temperatures of over
140°F on linens, cottons, rayons and acetates in an
alkaline condition and over 175°F on silks, wools and
nylons (even without alkalinity) will cause reducing sugar to
caramelize and produce brown stains, which are difficult to
remove.
Most of these reducing sugars are found
in three beverages: hard drinks, soft drinks and fruit juice.
Note: My spotting video, “The
Caplan Method of Stain Removal,” which includes my
comprehensive text (edited by Hal Horning) and handy spotting
board reference, is available in English, Spanish and Korean
(video only). A special disc for South America equipment is
also available through Golomb Group (e-mail: dm@golombgroup.com
or phone (800) 679-5856) or by this writer. A lecture and
demonstration are presented similar to my classes over the
years at IFI and SDA schools. This video and text are ideal for
training inexperienced spotters as well as a good review for
experienced spotters. Digesting, bleaching, oxidized oil stains
and caramelized sugar stains are discussed completely. An
article on “Removing Spots in the Cleaning Machine”
for perc and hydrocarbon/Stoddard solvents is included in the
text.
Also available is my video on
step-by-step shirt finishing which includes my comprehensive
text in loose-leaf form outlining each procedure for
single-operator and two-operator cabinet shirt unit using a
cabinet sleeve press. Proper forming of the collar using heated
collar formers is demonstrated. Each lay is demonstrated for
top quality and production with very little effort. Attractive
detailing and packaging of the hung shirt, padding, steam
pressures and timing are all discussed. A unique wash formula
for whiter whites and brighter colors and removal of grease and
body oils is included in the textbook.
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