How
To Waterproof Silnylon Fabrics
This article describes the rapidly
growing use of silnylon fabrics in the outdoor industry and offers advice on
waterproof maintenance and repair.
As used in the outdoor industry: Silnylon--silicone
impregnated ripstop nylon fabric
The past few years have seen an
explosion in the use of outdoor gear made from silnylon, especially the very
lightweight and strong fabrics. This
waterproof and windproof fabric is now used for many tents, rain canopies,
tarps, ground cloths, rain suits, ponchos, packs, pack rain covers, stuff
sacks, and clothes. Even the rain
canopies for our Speer Hammocks are made from this remarkable fabric. This modern wonder fabric has certainly
proven its usefulness in the world of outdoor gear.
Silnylon is even more popular in
the manufacture of lightweight parachutes and kites. Although often referred to as 'silicone coated' nylon, this is a
misnomer since the silicone, which is applied after the fabric is manufactured,
actually wets and soaks completely through the fabric, unlike the earlier
generation urethane-coated fabrics where the treatment remains on only one side
of the fabric. Silicone is replacing
urethane for outdoor use because it protects both sides of the fabric, is
lighter weight, and lasts longer.
This widespread use of silnylon
brings up the issue of durability. How
long will it be waterproof? Can it be
maintained and/or repaired? How? The good news is that the silicone, which is
primarily responsible for making the fabric waterproof and windproof, will last
for many years. The application process
thoroughly soaks the fibers of the individual threads themselves, thus ensuring
that the silicone completely impregnates the fabric. Regular outdoor use, such as stuffing or storing in a carry sack,
or deploying for rain/wind protection, do not cause deterioration of the
silicone; in fact, the treated fabric remains soft and pliable even at sub-zero
temperatures.
However, the silicone is slightly
water-soluble and repeated long exposure to rain, or repeated washings, can
render the fabric less than completely waterproof. Unlike urethane-coated fabrics, that are susceptible to
non-repairable deterioration over time, silnylon fabrics can be easily and
inexpensively re-treated when needed!
Consumer-applied silicone is
highly effective in restoring full waterproofing in most fabrics. Silicone liquids and sprays for this purpose
are readily available on the market today; they are inexpensive and can be
applied easily and quickly. Once-a-year
treatments are recommended for fabrics under normal outdoor use. Twice-a-year treatments may be needed for
fabrics that receive lots of use.
Fabrics exposed to rain only a few times a year, may not need
re-treatment for many years. However,
note that consumer-applied silicone may be less permanent than factory-applied
silicone. Washing with detergent also
removes a certain amount of silicone and multiple washings may significantly
reduce the ability of the fabric to repel water.
Silicone aerosol (w/ 10% silicone)
is probably the best option for most silnylon owners since it is readily
available and easily applied. While
several brands are available, Silicone Water-Guard®
is a popular one found at many outdoor retailers, including Wal-Mart. Ever-Dri brand, which comes in
aerosol or liquid, can be found at many military surplus and/or shoe
stores. ScotchgardTM
is perhaps the best-known silicone aerosol.
A search engine such as Google will
provide many Internet retail sources.
Silicone liquid (w/ 5-10%
silicone) may be more appropriate for treating seams since it allows
application with a small paintbrush or sponge.
This concentrates the liquid on the area of concern and limits 'over
splash'. A suitable brand is Aqua-Tite®;
however it is only available in 1 quart or larger bottles, which is far more
than most folks will ever need. I have
found a useful small bottle of similar liquid silicone with a handy sponge-top
applicator at some outdoor retailers, but the brand name is unknown. Ever-Dri, mentioned above, also comes
in small bottles with a dapper applicator.
Again, a search engine such as Google
will provide many Internet retail
sources.
Additional brands of silicone
aerosols or liquids can usually be found in RV and/or Marine stores. Silicone liquids used in the
Construction/Home Improvement industry may also function on fabrics; however,
the ones I've tried leave the fabric brittle and much darker in color.
Be sure and follow directions when
using silicone aerosol or liquid since the petroleum-based solvent carrying the
silicone is hazardous to your health and plenty of ventilation is advised
during application and drying. Quickly
worsening headaches are often my first indication that more ventilation is
needed!
Treatment consists of soaking the
entire fabric or area of concern making sure to wet both sides of the fabric by
applying silicone to both sides. If
treating seams, be sure to completely soak the threads as well as the fabric
that surrounds the seam. After the
first application has dried to the touch, a second application is recommended
to help ensure waterproof-ness. Two
aerosol treatments to an 8' X 5' piece of 1.9 oz/yd2 ripstop nylon
add about 0.6 oz to the total weight.
Note that silicone treatments do
not completely 'seal' fabrics or seams in the same manner as urethane
coatings. Instead, silicone simply
causes water to bead up on the surface exposed to rain, allowing it to run off
or evaporate instead of wetting the fibers and soaking through to the other
side. Thus silnylon is 'waterproof'
only up to a certain pressure; at higher pressures, water can be forced through
the fabric. Fortunately even a heavy
driven downpour does not generate enough pressure to cause well-treated
silnylon to leak.
Seams in your silnylon fabric
deserve special attention. They can be
treated with silicone liquids or aerosols as described above, or with seam
sealant glues. When silicone liquids or
aerosols are properly applied, as described above, they are often sufficient to
waterproof seams. However, greater
peace of mind may come from using silicone-based seam sealant glues.
Avoid the non-silicone-based seam
sealants, which are commonly used to treat seams in urethane-coated fabrics,
since they will not adhere properly to silnylon. Only silicone-based sealants should be used on silnylon.
While slower to apply than liquids
or aerosols, glues may last as much as twice as long before re-treatment is
required. Sil-NetTM is a popular and
readily available silicone-based seam sealant.
It can be purchased in 1.5-ounce tubes at most outdoors retail stores or
over the Internet--this should be enough to seal the seams in a small
two-person tent. Be sure and follow
directions on the tube and again provide plenty of ventilation. Lightly coating the dried seam with baby
powder is recommended to prevent it from sticking to the rest of the fabric
when stuffed into a carry sack.
The following homemade silicone
glue directions are taken from the book Hammock Camping, The Complete Guide to
Greater Comfort, Convenience and Freedom, by Ed Speer 2003 (see the
book at: http://www.hammockcamping.com).
A simple and inexpensive seam
sealant can easily be made from a 60/40 mixture of clear household silicone
sealant or silicone caulking and a solvent such as gasoline. Any clear silicone sealant or silicone
caulking from a hardware or home-improvement store works fine; it can generally
be purchased in quantities as small as 4 ounces, which is enough to seal
hundreds of tents. The solvent can be
automobile gasoline or camp stove gasoline; however, extreme caution is
necessary when using these highly flammable and toxic substances. The solvent dissolves the normally thick
silicone sealant or caulking and makes it much easier to spread on the seam,
after which the solvent evaporates and leaves the silicone in place. The solvent is not in contact with the nylon
fabric long enough to harm it. About
1/4 ounce of this mixture is all it takes to seal both sides of an 8' seam,
such as the one on the Speer 8 X 10 tarp (1/2"-wide, double stitched
seam). Avoid breathing the solvent
fumes by working in a well-ventilated area.
Mix the items in a small squeeze
bottle using the head of a nail as a plunger/mixer. If necessary, enlarge the spout's exit hole with a straight pin
heated in a small flame; hold the hot pin with pliers and keep the flame away
from the gasoline! If a suitable
squeeze bottle is not available, the items could be mixed on a paper plate and
spread over the seam with a plastic picnic knife. Let the sealed seam dry 48 hours and then coat it with baby
powder; otherwise it will continually stick to folds of the tarp when stowed
away.
Sun rot is probably a more serious
threat to silnylon than loss of waterproofing. You can replace waterproofing, but you cannot repair sun rot!
You can reduce sun rot by limiting exposure to sunlight; bright, direct
sunlight is particularly harmful. Try
to set up in the shade and remember to put away your tent or tarp during the
day.
With occasional re-treatment as
needed, your silnylon fabrics can remain in service for many years; even 10 to
20 years are not unreasonable expectations.
The good news is that with proper care you can enjoy years of service
from this wonder fabric!
....Ed
"Not To Worry" Speer Sep 29,
2003
Take a
hammock on your next wilderness trip
and
experience the wonder of nature all over again
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