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Opsak test
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Steve B
(geokite) - F

Locale: Southern California
Opsak test on 06/12/2012 11:35:22 MDT Print View

Method: place odor producing item in opsak, close opsak. Place opsak in normal ziplock bag (gallons size works well), close ziplock. Wait a day. Open ziplock, smell inside for odors that came through the opsak.

I tested the odor proofness of the opsak a while ago with esbit. It failed.
I tested the odor proofness of the opsak with garlic. It failed.

I emailed Locsak about this; they got back to me about the esbit, saying the bag works on food type smellables. They never got back to me about the garlic. No reply.

Is this test viable for determining if the opsak will keep the smell away from bears?
Thanks for your input.


Mike Oxford
(moxford) - MLife

Locale: Silicon Valley, CA
Potential for cross contamination on 06/12/2012 12:21:26 MDT Print View

How did you place the Esbit into the Opsak? How about the garlic? If you used your hands then it's possible you contaminated the outside of the Opsak when when you closed it. You may be smelling the residue from the Esbit or the oil from the garlic on the OUTSIDE of the Opsak; too faint to detect via smell until you closed it up inside a Ziploc and let the molecules permeate the air inside of the bag ... opening it then would give you a high enough concentration to pick up on.

Better: In a room with no drafts, wearing gloves, put the Esbit into a NEW Opsak via a long pair of tweezers/pliers/etc being very careful to not touch the zip area of the bag. Remove gloves, zip it shut. Wash the outside of the Opsak with hot soapy water. Dry it well, and then place inside of a NEW ziploc and shut it.

Even a small amount of a substance, over time, can saturate the air inside of a container enough to notice.


Greg Mihalik
(greg23) - M

Locale: Colorado
Re: Potential for cross contamination on 06/12/2012 12:36:54 MDT Print View

Excellent points Mike.

What is the protocol for handling your food and an OPSak in the woods?

Randy Martin
(randalmartin) - F

Locale: Colorado
Re: Re: Potential for cross contamination on 06/12/2012 13:05:03 MDT Print View

Those are very good points. The only way to be absolutely certain there isn't cross contamination is to wash your hands before opening/closing the Opsak. Truth be told there are likely mild smells of various kinds all over our gear. Truly a difficult task to maintain a neutral odor on everything.

Dustin Short
(upalachango) - MLife
Re: Re: Potential for cross contamination on 06/12/2012 13:11:15 MDT Print View

Greg, that is the crux of the problem of odors in the woods. Your gear may be perfect for any job, but if your procedures for using the gear are flawed or impossible to implement then it doesn't matter.

This is probably why so many people advocate bear-bagging all the time. You can't guarantee odor free bagging but you can guarantee that you'll make it difficult for a bear to reach your food (though of course not impossible).

Also, your body stinks, which means your gear stinks too. Opsaks are great for minimizing odor (so are ziplocs) but nothing is 100% in real world conditions. Even in a lab 100% is unheard of.

Mary D
(hikinggranny) - MLife
Opsak test on 06/12/2012 13:37:02 MDT Print View

My test involves dog kibble and my dog. (A dog's olfactory apparatus is far more sensitive than any human's.) Even I can smell his kibble through a quart ziplock freezer bag. After I put his kibble (inside the freezer bag ) into an OP sack, the dog completely ignored it, something he'd never do if he could smell anything resembling food! The OP sack was not new, either. I use two small OP sacks in my dog's pack (one on each side) to contain the quart ziplock bags with his kibble, in hopes that his pack won't end up smelling of dog food. So far, no issues. (The kibble of course goes into an Ursack at night.)

IMHO, the OP sack is a useful supplement to a hung food bag and an essential part of the Ursack system. At the very least, it cuts the smells way back so that the bag doesn't scream "FOOD" to passing varmints of various sizes.

Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: Opsak test on 06/12/2012 15:28:57 MDT Print View

"IMHO, the OP sack is a useful supplement to a hung food bag and an essential part of the Ursack system. At the very least, it cuts the smells way back so that the bag doesn't scream "FOOD" to passing varmints of various sizes."

A huge +1 Exactly the way it should be done, IMO.

Chad "Stick" Poindexter
(Stick) - F

Locale: Wet & Humid Southeast....
big fan of the opsak on 06/12/2012 18:43:49 MDT Print View

I am a big fan of the Opsaks. I always use one in conjunction with my food bag, which is most of the time a ZPacks Blast food bag (with the cinch top).

I have a trip coming up in 2 weeks, and have slowly been getting some of my food for this trip. I have been keeping it inside my 12 x 20 Opsak, which has been inside a Granite Gear UberLite 10L roll top bag. The Opsak has been sealed shut for about the last week, since I was last in it. I opened it up today though looking for a packet of Emergen-C and wow! I did not smell anything until I opened it up, and when I was like the smells had been waiting to escape! It was definitely a strong smell, and everything inside the Opsak is still in it's original packaging. There is an assortment of bars, some drink mixes, poptarts and some other stuff I can't remember right off the top of my head.

Anyway, like I said, I always use one. I will admit, when I am adding in that 1.3 oz for the Opsak into my spreadsheet, it kind of sucks...but I had rather carry it for a little extra protection. I still hang my food in bear country though.

Does, it work, I dunno...all I do know is that I have yet to wake up to find remnants of my food bag laying all over the place...instead, it is always hanging in the trees right where I left it.

I will admit too though, I do not wash my hands before handling the Opsak, so I know that there has gotten to be smells on the outside too.

Ken T.
(kthompson) - MLife

Locale: All up in there
Re: big fan of the opsak on 06/12/2012 18:51:04 MDT Print View

"when I am adding in that 1.3 oz for the Opsak into my spreadsheet, it kind of sucks..'

You don't hear that kind of talk anywhere but here!

Dale South
(dsouth) - M

Locale: Southeast
RE: Opsak test on 06/12/2012 19:11:59 MDT Print View

I put a ziplock back of peanuts in an opsak and place it on the ground in the woods behind my house which are full of squirrels. They never touched it. I placed an open can of cat food in a zip lock and in then in an opsak. I left it on my carport for two days and nights. Nether my cats or the neighbors cats touched it. Also the possums that constantly eat the cat food that we leave out never touched it. At least it appears to work for protection from small critters.

Elisabeth Chaplin
(elisabitch.) - MLife
OPSak. on 06/12/2012 23:29:37 MDT Print View

"Your gear may be perfect for any job, but if your procedures for using the gear are flawed or impossible to implement then it doesn't matter."

That's how I see it too.

Simply put, I have had a mouse chew through a brand new OPSak, first night out of Kennedy Meadows on my PCT thru hike while it was in my vestibule. While there is NO way of knowing if I got food odors on the outside of the bag while handling it (and yes I did zip it properly -- I'd been backpacking for over two months straight at that point, and had nine days of food heading into the Sierra in a high snow year, you bet your buttons I was a bit food obsessed/paranoid), the real point of it is that the OPSak was as clean and unscented as it was ever going to get at that point! The more meals I pulled in and out of it, the less unscented it would become.

In theory, odor proof, but in practicality it's really hard to keep gear clean -- so to rely on them because you've luckily never had a problem, or to put your faith in them because they're advertised to be odor-proof seems a bit eager in my opinion. They are awesome to hopefully reduce the chance that a critter would even take note of your food bag, and I still carry them on my trips for that reason. But I wouldn't be surprised if it happened again, and I wouldn't put all my eggs in that basket without some skepticism and understanding that I'm taking a risk, even if it's hugely less than not using an OPSak in the first place. For me, they're part of a system, not my one size fits all solution.

I like all the backyard testing though :)

Jeffrey List
(jlist) - M

Locale: Cape Cod
My test failed on 06/17/2012 14:49:35 MDT Print View

I put some smelly peanut butter and fritos in an Opsak, and also in a Zip-lock freezer bag. I was as careful as possible about not contaminating the outside of the bags, certainly much more careful than I could be while backpacking.

I burried both just under the leaf litter, about 10 feet apart, at a campground, and came back two weeks later.

Result: both chewed through and eaten by small-size critters.

Edited by jlist on 06/17/2012 17:13:27 MDT.

Dustin Short
(upalachango) - MLife
Re: My test failed on 06/17/2012 15:14:55 MDT Print View

There could also be a totally different reason for test failures that no one has brought up.

Maybe, just maybe, critters have learned that the smell and sound of plastic means there is a tasty treat inside! In which case being odor proof or not is useless, because the container itself is attracting animals!

I know my cat will spend hours liking a plastic bag, and that's without food, if she thought there were kitty treats it'd be even worse. We use mice and rats for intelligence tests while raccoons, bears, foxes, and other animals are all known for their wily picnic snatching behaviors. We're in an arms race to protect our food against the wild, and the wild is much hungrier than civilized folk ;)

John S.
(jshann) - F
Re: Re: My test failed on 06/17/2012 15:21:28 MDT Print View

opsak's are a waste of money to me.

Richie S
(LandRover) - F
Limit rather than eliminate on 06/18/2012 10:36:36 MDT Print View

I would have thought the object in practical terms is to limit the smell rather than eliminate it altogether, given the practicality of keeping the thing sterile.

If a critter stumbles across it and it literally nose to plastic, I'm sure there's going to be enough smell to make it worth testing to see if the contents are edible.

I'd just hope that the bags limit the smell enough to make sure that you're food isn't giving off odors that can be picked up from a long distance.

Daniel Cox
(COHiker) - F

Locale: San Isabel NF
Re: My test failed on 06/18/2012 14:21:32 MDT Print View

Two weeks in a campground introduces a huge margin of error. Without checking on it every day there's no way to say kids playing didn't find and compromise them.

I wouldn't expect anything short of a locked steel box to last two weeks on the ground.

Edit to add: I doubt anything on this planet is truly odor PROOF to an animal with a nose like a bear, short of a vacuum sealed thermos and maybe even not even that at close range. The idea is to make everything else in camp relatively more smelly to animals. Non habituated animals smell people and say "I'll pass"

Edited by COHiker on 06/18/2012 14:26:03 MDT.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Re: My test failed on 06/18/2012 16:40:54 MDT Print View

Many years back a dog trainer, who was an active forum member, did a series of odor blocking tests using different bags. The OP Sak was the only one the dogs couldn't smell the contents of.

Edited by richard295 on 06/18/2012 22:13:50 MDT.

Will Tatman
Primary Bear-proofing on 06/18/2012 21:11:33 MDT Print View

Out of curiosity: Does anyone else on here use an Opsack as their primary means of excluding bears from their food? I was bear-hanging until a triple-crowner indicated he merely put his food in an Opsack and used it as a pillow.

Maybe it was just the amount of guts that method seems to require, but the idea of no more hangs appealed to me, and I finished my GET thru hike with just an Opsack and no issues (in the bear-active Manzanos and Sandias no less).

Anyone else live out on this edge?

Sam Farrington
(scfhome) - M

Locale: Chocorua NH, USA
OPsak test on 06/18/2012 21:39:58 MDT Print View

Thanks for the posts about the great tests by Mary D and others with the help of our canine friends.

FWIW, here's the thread from a test done last year:

As noted, I only use the Opsaks for caches and double bag. This way I can be more sure that odors do not get on the outside of the bags. So far, that has worked OK, even when the bags have been hung in Ursacks in the mountains for several weeks before I reach them.

For daily use while trekking, I would be much more leery, and would certainly not dispense with hanging a bear bag just because of the Opsak. I'm surprised by the number of posts about food in tents. I do not allow it even in my pack - the Ursack is strapped to the top of the pack, and not opened until removed from the pack.
Suppose practices have more to do with what animals inhabit the area trekked.

Some time ago, I had a bear keep me up most of the night because of some blueberry cool-aid kept in a Nalgene bottle next to the tent. No more of that.

Brian Lindahl
(lindahlb) - MLife

Locale: Colorado Rockies
Re: OPsak test on 06/19/2012 15:35:28 MDT Print View

OP saks don't work if the critter can see the food. Not all animals rely solely on sense of smell to identify food. I'm not surprised the critters in the campground found the 2-week bag and got into the food. Same thing happened to me last year. Add a normal stuff sack around it, and you likely would have gotten a different result. An opaque (i.e. black) opsak would be a nice item to have - curious if it would have produced different results in your 2-week test.