EDIT: GSI Outdoor 16 oz Lexan Flask - Andrew Mytys
- Andy overall a nice report. I enjoyed reading about your use of
the flask, and learned some good tips. Your photos add a lot to the
report. Just a few minor edits for you. I guess the protocol is to
repost the report once you've corrected it, even though I know you
> a handy 1 oz (30 ml) "shot" cap. The flask has a slim and flatComment: Instead of using "one's hand", I would prefer to see you
> profile that's comfortable when held in one's hand, and discretely
> fits into deep pant and jacket pockets. The Lexan flask is
use "my hand" or even "the hand".
> construction of water bottles. To start, Lexan is durable - ouncefor
> ounce, it is stronger than steel.Comment: Do you have a source for this claim? Maybe you could
reference the source?
> to -40° F (-40° C). It is resistant to staining and odors, andwill
> not absorb any tastes from previously held contents.Comment: From personal experience I would argue this point to some
extent. Occasionally it will hold taste/odors from previous foods
or beverages. I had some nasty tasting chili flavored hot cocoa on
one trip. Perhaps consider adding this is a manufacturer's claim.
> In the 3-season, this translates into my carrying a 45°F (7°C) bagdrop
> that weighs just under one-pound (450 gm). Should temperatures
EDIT: For 3-season camping (or backpacking) instead of "In the 3-
> warming the inside of a sleeping bag. I've also found that my feetin
> can get really chilled after being out in the cold all day - as my
> feet sweat, the socks in my boots get damp, and this in turn can
> cause circulation issues in my feet, especially when I've arrived
> camp and taken my feet out of my boots.EDIT: I've found that my feet can get really chilled
>Typically, I remove the dampthen
> socks from my feet, let my feet air out and dry for about a minute
> (dry winter air evaporates moisture from my feet quickly), and
> put on a dry pair of 200 weight fleece socks onto my feet.EDIT: using "on" and "onto" is redundant. Either use "put a dry
pair of 200 weight fleece socks onto my feet." Or use "put on a dry
pair of 200 weight fleece socks". I think the average reader would
realize they go on your feet. :)
> boiling water, fill my flask, and then, thanks to the flask's slimEDIT: "both the flask and my foot into my slipper" (remove "in").
> profile, I can slide both the flask and my foot in into my slipper
> (see bio for shoe size).EDIT: please spell out "biography"
> a short trip. Then, while on my dayhike, I can cool myself bysip
> pressing the Lexan flask against my kneck or under my shirt, and
> iced-water as the frozen flask slowly thaws out.EDIT: neck (spelled incorrectly as kneck). Also, ice water instead
> There are other Lexan water bottles on the market, but I've foundwill
> that their rounded shapes means that they tend to roll around at
> and that their wider profile means that they can't slide into theEDIT: remove a few "that"s from the sentence. "I've found their
> tight spaces that I tend to place my GSI Lexan Flask into. For me,
> the Lexan flask is a clear winner!
rounded shapes mean they tend to roll around at will and their wider
profile means they can't slide into the tight spaces I tend to place
my GSI Lexan Flask into"
- Thanks for the edits, Pam. I incorporated all the edits. In terms
of the Lexan not absorbing tastes, I merged the statement into
the "resistant" sentence so that it now reads like it's just
resistant to absorbing tastes, which I think is a fair way to handle
I put quotes around the "3-season" (In the "3-season") - I'm
suggesting this to be a personal style issue, as I tend to refer to
backpacking having two seasons - the "3-season" and "winter,"
following tent conventions.
Anyway, here's the updated report.
GSI Outdoors 16 oz Lexan Flask
Date Published: January 22, 2006
Tester's Biographical Information:
Reviewer: Andrew Mytys
Homepage: Andy's Lightweight Backpacking Site
Height: 6'1" (183 cm)
Weight: 185 lbs (84 kg)
Shoe Size: Mens 10 (US); 9 (UK); 43 (EU); 280 (JP/KR)
I live in Michigan and have been hiking seriously for 15 years,
although I've camped since I was 6 years old. I consider myself a
lightweight hiker. I carry the lightest gear I can get my hands on
which will provide a comfortable wilderness experience and adequately
support the goals of my trip. Unless my goals are time/distance
oriented, my pace is always slow. I rarely exceed 1.5 miles (2.4
km)/hour. I rest frequently, hike long days, and enjoy whatever
nature throws my way.
Manufacturer: GSI Outdoors
Item: GSI Outdoors 16 oz Lexan Flask
Year of Manufacture: 2002
Volume: 16 fl oz (475 ml)
Listed Weight: 4 oz (113 gm)
Weight as delivered: 4.2 oz (120 gm)
I have owned the GSI Lexan Flask for three years. During that time,
it has accompanied my on most backpacks and dayhikes, year round. I
would estimate I have carried it on 40 overnights in addition to a
large number of dayhikes.
The GSI Outdoors 16 oz Lexan Flask is a compact and durable flask
made for carrying liquids. It has a capacity of 16 oz (475 ml), with
a handy 1 oz (30 ml) "shot" cap. The flask has a slim and flat
profile that's comfortable when held in my hand, and discretely fits
into deep pant and jacket pockets. The Lexan flask is transparent
gray in color, making it easy to determine the level of liquid
inside. The flask seals tightly and is leak-proof, thanks to a rubber
gasket that can be found on the inside of the cap, at the base of the
The GSI Outdoors Flask is constructed of Lexan - a thermoplastic,
polycarbonate resin, made by GE's plastic division. Lexan has some
fantastic properties that make it advantageous for use in the
construction of water bottles. To start, Lexan is durable - ounce for
ounce, it is stronger than steel. Lexan remains strong and shatter
resistant whether exposed to very hot or very cold temperatures. This
means that liquid held in the flask can be frozen or, conversely,
that boiling water can be poured directly into the flask without the
container becoming soft, changing shape, or developing holes or
cracks in its structure. Lexan is rated durable in temperatures down
to -40° F (-40° C). It is resistant to staining and odors, and
absorbing any tastes from previously held contents.
At 4.2 oz (120 gm) in weight, there are lots of lighter solutions to
carrying around 16 oz (475 ml) of water. Why, you might ask, would
a "lightweight backpacker" such as myself carry a relatively heavy
container when a simple 1 oz (28 gm) plastic pop bottle would work
just as well?
The reason I have resolved to add this piece of gear to my packload
lies in its heat-resistant properties, and in the shape of the flask
itself. In combining these two features, I have found that the GSI
Lexan Flask makes for an excellent hot-water bottle. This, in turn,
has enabled me to carry a much lighter sleeping bag than I would
without the flask, and the Lexan container now doubles as additional
warmth in times when the weather surprises me with much colder
temperatures than were forecast. No matter what the season, the Lexan
Flask can be used to augment my sleeping bag's comfort range by as
much as 15°F (8°C).
In the "3-season", this translates into my carrying a 45°F (7°C) bag
that weighs just under one-pound (450 gm). Should temperatures drop
to a point where I am uncomfortable, I simply pour the contents of my
GSI Flask into a pot, bring it to a boil, then pour the water back
into my flask and bring this into my sleeping bag. I find that a
flask filled with boiling water is too hot to the touch, so I pull
out a liner glove or sock, slide the hot flask inside, and then
either put this onto my chest or between my legs. Between the heat
trapping capabilities of my sleeping bag and my own body heat, tests
have shown that the Lexan flask will remain HOT for over two-hours.
After this period of time, the flask can be removed from the
protective liner and then be placed directly onto the skin, allowing
it to continue its warming effect.
Eventually, the flask no longer delivers any effective warmth but, by
this time, it is morning and time to get moving anyway. The contents
of the flask are still warm and drinking from it can provide
Of course handling water in the middle of the night in close
proximity to a down bag can be risky. Personally, I've had
no "accidents" to date with the system I've described. I have never
felt that I've been fortunate in this regard - the opening to the
flask is wide enough to use confidently, even when handling boiling
water. Add a little caution to the mix, and I get by even while half
asleep and not wearing my glasses. The cap on the flask provides a
secure seal, and the Lexan strength means that I am not worried about
leakage should I roll over onto it while sleeping.
In winter conditions, the GSI Lexan Flask can continue to be used in
warming the inside of a sleeping bag. I've found that my feet can get
really chilled after being out in the cold all day - as my feet
sweat, the socks in my boots get damp, and this in turn can cause
circulation issues in my feet, especially when I've arrived in camp
and taken my feet out of my boots. Typically, I remove the damp socks
from my feet, let my feet air out and dry for about a minute (dry
winter air evaporates moisture from my feet quickly), and then put a
dry pair of 200 weight fleece socks onto my feet. This is followed by
a pair of down slippers, and I then place my feet into my sleeping
bag. At times, my feet still feel cold and this is when I use the GSI
Lexan Flask. I fire up the stove, turn some snow into boiling water,
fill my flask, and then, thanks to the flask's slim profile, I can
slide both the flask and my foot into my slipper (for shoe size, see
Many hikers like to dry damp clothes in the winter by positioning
them against their skin or in the footbox of their sleeping bag while
they sleep. I'm not a proponent of this system, as any drying that
occurs increases the amount of water vapor that the sleeping bag has
to manage - the result is often that the sleeping bag loses loft and
heat-trapping capability. As luck would have it, snow melting is a
time consuming task. As each pot of snow comes to a boil, I rotate
the water into my GSI Lexan Flask and start melting the next batch of
snow. While I wait for the snowmelt to boil, I take the hot flask and
place it into my liner sock. I watch the steam rise into the air as
the sock dries on contact. Any dampness in my thin, Coolmax liner
socks dries in less than a minute - I repeat the process with my
thicker, ragg wool hiking socks. As the water in my pot comes to a
boil, I pour the water from my flask into a larger water container,
then pour fresh boiling water into the flask in order to maintain
Of course, a hot GSI Lexan Flask can be used to dry more than socks.
Often times, I find that the shell of my jacket, or sleeping bag
footbox, is damp or even wet. A flask filled with boiling water can
be comfortably held by its neck and moved about over the wet area in
a quick, circular motion until it is dry (see image, above). A flask
filled with boiling water does tend to be hot, so I keep the bottle
moving to mitigate any risk of melting synthetic materials.
This "backcountry iron" technique works like magic, and in a matter
of minutes my equipment is dry once again.
The advantages of the GSI Lexan Flask continue into the summer, when
I place the flask filled with water into the freezer overnight before
a short trip. Then, while on my dayhike, I can cool myself by
pressing the Lexan flask against my neck or under my shirt, and sip
ice water as the frozen flask slowly thaws out.
There are other Lexan water bottles on the market, but I've found
their rounded shapes means they tend to roll around at will. Their
wider profile also means they can't slide into the tight spaces I
tend to place my GSI Lexan Flask into. For me, the Lexan flask is a
Aside from a few scratches, the GSI Lexan Flask is as good as new.
The rubber gasket ring inside the cap remains functional, and the cap
continues to provide a tight and leak-proof seal.
Recommendations For Improvement:
. The GSI Flask has a line from the production mold going around its
parameter. The manufacturer would do a great service in delivering a
product that had a smooth mold line all around. My flask had a rough
bottom, a characteristic that I discovered when I heard and felt a
catch against the inner lining of my Western Mountaineering sleeping
bag. Thankfully, morning and post-trip inspections verified that
there was no damage done (whew). Before considering using the flask
as an in-bag hot-water bottle, buyers should be prepared to take some
fine-grade sandpaper to the bottom of the flask, and any other rough
spots found, in order to smooth out jagged areas.
. The manufacturer could include a message on the packaging warning
users that the flask's cap contains a rubber gasket ring inside, and
that at times this ring can work its way loose from the cap. During
those times when the flask was sealed with boiling water inside and
then allowed to cool, I noticed that the gasket either adhered itself
to the top of the flask's opening or slipped loose on the inside of
the cap while it was being opened - I've even had the gasket fall out
of the cap. Fortunately, the first time that the gasket worked its
way loose I noticed it, and I've since gotten into the habit of
verifying that the gasket is in its proper position, at the base of
the cap's threads, before closing my flask. Testing indicates that a
missing or improperly installed gasket will result in the flask
leaking. As I routinely have the flask filled with scalding water
next to my skin, it's important for me to verify that the gasket is
installed correctly before I screw the flask's cap on.
- --- In BackpackGearTest@yahoogroups.com, "Andy Mytys" <amytys@...>
> Thanks for the edits, Pam. I incorporated all the edits. In
> of the Lexan not absorbing tastes, I merged the statement intohandle
> the "resistant" sentence so that it now reads like it's just
> resistant to absorbing tastes, which I think is a fair way to
> it.Fair enough. One small edit -
"It is resistant to staining and odors, and absorbing any tastes
from previously held contents."
remove the first "and" and replace with a comma. i.e. "It is
resistant to staining, odors, and absorbing any tastes...
> I put quotes around the "3-season" (In the "3-season") - I'm
> suggesting this to be a personal style issue, as I tend to refer
> backpacking having two seasons - the "3-season" and "winter,"I still don't think "In the "3-season" " sounds grammatically
> following tent conventions.
correct, but I will not argue the point. With the quotation marks
I'm willing to chalk it up to a style issue.
The report looks nice. Congratulations. Upload when ready.