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My scumbag opsack is now putting out an odor! :-P
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Kevin Burton
(burtonator) - F

Locale: norcal
Re: Re: Barrier bags on 08/06/2013 13:12:48 MDT Print View

yeah.. dumb luck. I don't use one and haven't had a problem either.

reminds me of this simpsons quote:

Homer: Not a bear in sight. The Bear Patrol must be working like a
Lisa: That's spacious reasoning, Dad.
Homer: Thank you, dear.
Lisa: By your logic I could claim that this rock keeps tigers away.
Homer: Oh, how does it work?
Lisa: It doesn't work.
Homer: Uh-huh.
Lisa: It's just a stupid rock.
Homer: Uh-huh.
Lisa: But I don't see any tigers around, do you?
[Homer thinks of this, then pulls out some money]
Homer: Lisa, I want to buy your rock.
[Lisa refuses at first, then takes the exchange]

Willie Evenstop
(redmonk) - F

Locale: Greater Yellowstone Ecosystem
Work for me on 08/06/2013 13:22:51 MDT Print View

Ive been happy with the odor proofness. Perhaps the problem is that they are not the OP model, or that zipper closures are really tricky.

Randy Martin
(randalmartin) - F

Locale: Colorado
Re: Re: Re: Barrier bags on 08/06/2013 13:37:47 MDT Print View

"yeah.. dumb luck. I don't use one and haven't had a problem either."

The dumb luck comment was me just being facetious. I have had no issues when others in camps around me have. I agree with Bob's comment that the closure system can be tricky sometimes and requires a fair amount of pressure to seal properly.

Edited by randalmartin on 08/06/2013 13:39:09 MDT.

Marko Botsaris
(millonas) - F - MLife

Locale: Santa Cruz Mountains, CA
Re: My scumbag opsack is now putting out an odor! :-P on 08/06/2013 22:11:44 MDT Print View

"So this is ironic... my opsack now smells like peanut butter and curry powder."

I think this must somehow be related to the immutable law of conservation of smell. I wonder, where do the smells go when they are proofed against? It seem unreasonable if not an outright violation of the laws of God and Nature, does it not, to demand that the smell BOTH outside and inside the opsack vanish.

Edited by millonas on 08/06/2013 22:13:23 MDT.

Brett Peugh
(bpeugh) - F - M

Locale: Midwest
how to use opsaks now? on 08/07/2013 10:51:50 MDT Print View

I got some awhile ago but really have never had a chance to use them in the last few years. What would they be good for now other than trying to keep animals from smelling the odors?

Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: Re: Nylobarrier litetrail on 08/07/2013 17:09:00 MDT Print View

"I bought both the odor proof bags and the pack liner. Each one developed punctures on their first use (and I am not rough on my gear at all)."

I can't speak to the pack liner, but I have used Nylobarrier bags several times each
and they are still puncture free. For me the technique is to use them as a liner for a stuff sack, which can then be used to hang my food when in bear country. The stuff sack protects the Nylobarrier bag from abrasion, punctures, etc. I wash them between trips, and they are then good to go for the next one.

Colin Krusor

Locale: Northwest US
Sources on 08/07/2013 17:41:06 MDT Print View

Rafi, the bags in that ebay listing look similar to the bags I use (but smaller). The Sorbent Systems page has bags of many different kinds, though.

Sam Farrington
(scfhome) - M

Locale: Chocorua NH, USA
smelly opsack on 08/18/2013 21:19:44 MDT Print View

This year marks the third time opsaks were used for caches in Colorado wilderness areas. This year for over a week, and the cache remained untouched. There was also the test in the national forest near home, mentioned in a post on the BPL article, with the link to the thread.

Clip'n seal clips or the like from Amazon are essential with opsaks to insure that the seal is tight.

On all three occasions, a week's food for moi and 2 dogs was double bagged in opsaks,
clip'n sealed, and 4 bags were placed in a coated Spectra Ursack (the green ones - no longer sold) and hung about 20 feet high. If a bear did smell it, it would be easy to get down, but they are hung to avoid being moved by lesser beasts.

When unpacking opsaks, the odors are very strong, as they are trapped in the sacks for long periods. So, yes, they smell a lot.

While BPL has a long history of superb test articles, the one on opsaks was total nonsense.

Would almost like to see one of the caches fail at this point, just to raise some question ... but only almost. As earlier noted, opsaks would probably not work very well for carrying food, as the repeated removal and replacement of food in the sacks would contaminate their exterior with odors. But for caches, no failures yet.

Or maybe the bears have all left the Colorado wilderness areas, and I am way off base.

Colin Krusor

Locale: Northwest US
Tests on 08/19/2013 00:34:24 MDT Print View

You hung your food 20 feet up, later found it intact, and so decided that Opsaks are odorproof.

If I did your test, (hanging food-filled Opsaks 20 feet up for a week and later finding them intact) and then decided that this means that Opsacks make things invisible, what would you say about my conclusion?

I'm glad that your food cache was untouched, and maybe Opsaks are odorproof and they are the reason. But you didn't test the odorproofness of Opsaks.

I'm curious about your opinion that the locker room test described in the BPL article was nonsense. I don't see it that way, but I'm willing to learn.

Edited by ckrusor on 08/19/2013 10:13:40 MDT.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Tests on 08/20/2013 22:04:33 MDT Print View


I hung a Opsack from a Joshua Tree and no bears got to it. Must be odor-proof.

I like the method of the original dog-test, given the short time and other limits.

Sam Farrington
(scfhome) - M

Locale: Chocorua NH, USA
Opsaks on 08/21/2013 22:28:18 MDT Print View

Methinks you read too fast.
The caches have been used now for three summers in three wilderness locations, not to mention the test in the forest at home (we have lots of bears).

As for the article, the basis for my opinion was posted there at length for anyone who wishes to read it. The link to the thread about the home test was also provided.

Hume was a great philosopher, but at some point, if the pool ball keeps going into the pocket, you have to give credit to the player.

Edited by scfhome on 08/21/2013 22:30:06 MDT.

Colin Krusor

Locale: Northwest US
Testing on 08/22/2013 15:07:22 MDT Print View

Samuel, I don't know where to start. I agree that testing the function of something in a lab (or a locker room) is not the only way to learn about it. Testing under more realistic conditions is useful, if those tests are planned well. In my opinion, the tests you did were not planned well and they don't show what you think they show.

This is my understanding: you have used Opsaks for storage of food caches for up to a couple weeks and an animal has never breached one. Also, you did a test in which smelly foods were hung in bags and an animal got into the one that had no Opsaks. In that test the bags were arranged like this:


Where the box is the smelly stuff, the red are the ziplocks, the black are the Opsaks, and the green are the stuffsacks. Is this right?

Sam Farrington
(scfhome) - M

Locale: Chocorua NH, USA
Opsaks on 08/22/2013 19:25:48 MDT Print View

Nice diagrams. They seem about right.
How many treks would I need to successfully use the Opsacks for caches before you think them worthwhile? Just wonderin'.

Colin Krusor

Locale: Northwest US
Tests on 08/23/2013 12:47:06 MDT Print View

I'm convinced. I'm convinced that what you're doing is working. If I was going on a trip with you I would ask you to put my food with yours because you seem to have found a good method.

I share lab space with a colleague who does a lot of isolation and identification of parasites. And, like you, her methods always seem to work. I recently developed a new method for isolation of parasite cysts and oocysts from water samples, and she and I compared the new protocol with her standard protocols. We did each of them together. As we went through hers, I asked questions about why she did things the way she did. Some of her answers didn't make sense. She insisted on using test tubes of a certain color, and arranging supplies on the benchtop in a certain way, and doing the work at a certain time of day, because ever since she started doing it that way it has ALWAYS worked. It was superstition.

I think something similar is going on with Opsaks. Suppose a person has twenty years backpacking experience, and they have hung 3000 food bags from branches in that time. Thirty of those (1%) were damaged by animals. Then, that person acquires an Opsak/Nylobarrier/Ursack/RatSack/etc. and uses it for 100 food hangs over two years. No animals get to the food. If that person is like most of us, they will be convinced that their new tool (Opsak/Nylobarrier/Ursack/etc.) is wonderful and it must do exactly what the manufacturer claims (odorproof, toothproof, etc.). This person will become convinced of this after 100 nights (maybe after 10 nights) even if, in the past, they had numerous stretches of 100 consecutive unbreached food hangs without the new tool.

Ari's locker room Opsak test was well designed and executed. Your objection that it lacked odor-free negative controls is wrong (the dogs checked for pre-existing scents like foods before the test), and the difference you allege between drug dogs and wild animals is also wrong (not substantial or relevant). In contrast to Ari's decent (but not perfect) test, the tests I've read about that purport to show that Opsaks are odorproof are so bad in so many ways that I don't know where to start assessing them. Your test, for example, does not at all test what you think it tests.

First, you compared the Opsaks to nothing, not to ziplocks (because both bags had ziplocks). This is not valuable. Wrapping an odor packet (composed of food in ziplocks) in wet newspaper or dollar bills or band aids is also better than nothing. This says nothing about Opsaks. It just demonstrates that, given two choices, an animal will be more attracted to food that is wrapped in fewer layers.

Second, you tested preference, not detection. The animal might have detected both but chose the smellier one; it might have eaten from the Opsak one if it had been the only bag there. The animal left food in the bag it raided, so it might have chosen not to breach the Opsak bag because it was full. Ari's locker room experiment tested detection.

Third, because n=1, the animal might have just eaten from the first bag it came to, as far as we know. This problem is the reason that good experiments have larger sample sizes. And twenty experiments each having a sample of n=1 do not equal one experiment with n=20. A lot of n=1 experiments that can't prove anything do not add up to one big experiment that proves something.

Fourth, I'm not sure that the question that your test sought to answer is a question that anyone is asking. Opsaks are clearly better than nothing and they are almost certainly better than one standard ziplock because they're made of the same material (polyethylene), just thicker. Opsaks are just thick polyethylene bags with crappy ziplock closures, despite claims by Loksak that they are a "completely odorproof" "new generation" material.

My claim is that Opsaks are much more expensive and no better than multiple standard ziplocks, and, if a person really wants to try an odor barrier, it makes much more sense to use a real barrier bag (like those described earlier in this thread), which are cheaper than an Opsak and orders of magnitude more odorproof than an Opsak or many standard ziplocks.

All we want is a method that performs well, and you have that. I think you should be happy with your technique. My point is that, in the long run, it can prove useful to know why something works. It is impossible to improve something (by eliminating unnecessary parts, for example) if our understanding of its function is superstitious.

Sam Farrington
(scfhome) - M

Locale: Chocorua NH, USA
Opsaks on 08/23/2013 23:07:56 MDT Print View

Appreciate the great deal of thought you have given to this issue.
You again commented to the effect that "Your test, for example, does not at all test what you think it tests."

I'd like to see whatever I said that suggested what you think I think I was testing. I try to make zero pretense on this site at any kind of scientific training, even to the extent of frequently commenting on my lack of it. A concern arose on reaching the age and physical condition where caches became essential for longer treks. So the desire was to see what would happen in two identical situations if Opsaks were added in one and not in the other.

Your lab partner may be superstitious or prone to unnecessary protocol. That is very common in many professions, and I run into it all the time, including with myself. But whatever her issues may be, you should not paste me with it. She is she, and I is me.

I've never been much of a bear bag hanger, except once when I wanted to impress a lady who was packing with me. Just lazy, or tired after packing all day, I guess.
But leaving a bag out alone by itself for over a week is another matter altogether. When this became necessary, I wanted some reassurance before using the caches, and risking a ruined trek. I posted here exactly what I was going to do, and there was not one whiff of a suggestion by anyone about how it could be done better. So I proceeded, and you know the rest. Except that after the no-Opsak bag was twice raided, it was removed and the Opsak bag left up alone unmolested for a month or so. I later updated the thread to that effect. And when I said we have lots of bears here, I meant it. Bears come from the forest into our back yards whenever there is any food around. My neighbor had a dumpster that the bears couldn't get into, but they hung around at night constantly, so he finally had to get rid of it. We have to keep trash containing any trace of food in our basement until it goes to the landfill.

Your comments about the bags being the same material, with some just thicker, are not supported by any evidence. From common experience, I know that plastic bags are made of a multitude of materials, with varying resistance to penetration by water, odors (gasses), etc. If there's more out there about the Opsaks being the same material, please post about, if you have the time.

As for Ari's dogs, I read the article carefully, and did not see documented the rigorous pretesting that you refer to. He says it was a concern, but very little about what was done about it. As earlier noted, those lockers could have had any number of things in them at an earlier time, not to mention how the dogs' could have been affected by their earlier training. Again, the best way to deal with this is to make the test as true to life as possible, and the article did just the opposite.
However, I suspect from your posts this is one issue we are not going to agree upon, and it may well be wisest just to accept that.

Agree that the LiteTrail bags are worth a shot, but not before I see what the local bears do with them. If you have some simple ideas how that can be done better, please let me know.

What concerns me a bit is your determination to take issue. It makes me wonder if this is more about ego gratification than truth-finding. There is a lot of that on this site, way too much IMO. Fortunately, most are OK with expressing their opinions and accepting that others feel differently. I guess that's what we probably need to do in this case, assuming we are both capable of it. Some are not. That's life.

Edited by scfhome on 08/23/2013 23:08:44 MDT.

Colin Krusor

Locale: Northwest US
Bags on 08/24/2013 14:13:45 MDT Print View

It goes without saying that we appear to disagree. We each recognize and accept that, I assume. I see no harm in disagreeing, and I also see no need to run from it. A good debate can bring interesting information to light and improve one's understanding of a topic. Given your long and numerous posts, it seems that, like me, you are interested in this topic. The decision to participate is yours.

"Your comments about the bags being the same material, with some just thicker, are not supported by any evidence."

Debating things that are obvious isn't interesting to me. Please just read the Loksak website. They explain that Opsaks are made of polyethylene, including this sentence: “These resealable, washable, polyethylene bags are watertight, airtight, and odorproof, so they prevent animals from sniffing out your edibles and toiletries." There are, as you say, many different kinds of plastics. But commonplace ziplock food storage bags are polyethylene, and they are clearly thinner than Opsaks. This is common knowledge and easy information to find.

"As for Ari's dogs, I read the article carefully, and did not see documented the rigorous pretesting that you refer to. He says it was a concern, but very little about what was done about it. As earlier noted, those lockers could have had any number of things in them at an earlier time..."

I think this criticism of yours seem poorly thought out. In the article about the locker room study is this sentence: "Prior to beginning, one dog and handler team conducted a locker-room search to rule out the possibility of drugs on site that were not part of the study." So, any pre-existing odor that might throw the dogs off would have been identified before the test. However, drug sniffing dogs are specifically trained to overlook all non-drug odors. People commonly attempt to use other odors to conceal stashes of drugs, and the dogs are trained to not be distracted by those. The dogs were only looking for the odor of the material in the test bags, which is ideal for testing the odorproofness of the bags. Also, you have to choose between complaining that this test had too many complicating circumstantial factors and complaining that the circumstances of the test didn't have enough realistic complexity. Wild animals seeking food are surrounded by lots of other odors, too. And, like the drug dogs, the odor they are trying to pick out from the background odors is the odor of the stuff in the bag.

There are a few points that are obvious. This information is available from many sources online and I'm not interested in debating it:

1. Opsaks are made of polyethylene

2. Polyethylene is an abysmal odor-barrier material compared to nylon, metallized plastics, and foil.

3. In some industries it is crucial to have effective odor barrier materials. Companies in those industries don't use polyethylene because, compared to other materials, it isn't an effective odor barrier.

4. Real barrier bags are cheaper than Opsaks but similar in weight.

This is all we need to know. If you doubt any of these, please just look them up.

This in no way means that anyone using Opsaks should replace them. As your test results suggest, they are better than nothing. And your food cache experience shows that, for you, they work well enough. I think anyone who is using Opsaks now, and having good results, should continue to use them and not worry about this topic.

This is my only claim: if one is considering acquiring an odor barrier bag, it doesn't seem to make sense to consider Opsaks, because real barrier bags are cheaper, similar in weight, and made of materials that are better barriers. If you disagree with this statement, you are welcome to explain why.

Sam Farrington
(scfhome) - M

Locale: Chocorua NH, USA
Opsaks on 08/25/2013 18:27:09 MDT Print View


A good debate is OK, but there a "few" points you're not interested in debating, hah-hah.

But I think your posts are valuable in suggesting alternatives. Although you do not name them, several other posters mentioned the NyloBarrier bags form Lite Trail, that are much less expensive, larger, and a lot easier to use than Opsaks. Frankly, the Opsaks are a pain in the neck, just not as big a pain in the neck as arriving at a cache in a remote area after a week of hiking, finding bears got to the cache that was to provide food for the next week of packing, and having to bail out. I've not yet had to bail out for this reason, but have for other reasons, and it was an incredible bummer.

So next spring, when our bears come out, I will return to the small clearing in the forest behind the house and see how the Nylo bags do next to the Ziplock freezer bags used before. Can't wait to post the results. Note: The Ziplocks now have double sealing strips.

Would be interested in any suggestions you might have for the test.

Tom Kirchner
(ouzel) - MLife

Locale: Pacific Northwest/Sierra
Re: Opsaks on 08/25/2013 20:02:08 MDT Print View

"I will return to the small clearing in the forest behind the house and see how the Nylo bags do next to the Ziplock freezer bags used before. Can't wait to post the results."

Excellent! I will very much look forward to hearing your results. One suggestion, if you haven't already thought of it: After putting your food in the Nylobarrier bag and sealing it, wash your hands thoroughly and then seal the first bag in a second one to eliminate the possibility of scent traces on the outside of the first bag attracting animals. This is SOP for me when I am in serious bear country.

Colin Krusor

Locale: Northwest US
Ideas on 08/25/2013 20:05:29 MDT Print View

Samuel, I'll give it a little thought. If I have any ideas for your test, I'll send them along.

By the way, I should mention that disagreeing with you has been pleasant, thanks to you. Contention can take the fun out of a good debate, and make it unproductive, but your good natured posts (despite my occasionally abrasive tone) have made for an enjoyable discussion. It is appreciated.

Loki Cuthbert

Locale: Portland, OR
Re: BPL Article.... on 08/25/2013 22:10:14 MDT Print View

I think the article was well written and proved without a doubt that the bags are not completely odor proof, but I don't feel like the article addresses how useful "odor proof" bags are for their intended use.

The intended use of OP bags is to prevent the smell of food from attracting wild life. I strongly feel that when properly used OP bags reduce the amount of smell to the point that it would not peak the interest of most wild life. Animals don't track down miniscule amounts of smell because there is no food reward associated to tracking down those scents.

Drug dogs on the other hand are TRAINED to sniff out miniscule amounts of scents and are rewarded with food, play, being petted. Of course they are going to pay attention to the most miniscule amounts of scent and focus on tracking it down because they have been trained to associate following those scent trails with receiving a reward.

Don't go swearing of your OP bags just yet. I use the nylobarrier bags inside a stuff sack. Every once in a while I get home and I don't sort out the last bits of my food bag for a day or two. My pitbull who has chewed through a suitcase to get to an un-opened summer sausage has never payed attention attention to my food bag.