Valved Coffee Bags with a Rubber Band

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Ken5
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#1: Post by Ken5 »

When closing a bag of beans I usually press all the air out of the valve after sealing the bag. Does not take long before more air can be pressed out the valve.

The other day I wrapped a rubber band around the bag to keep the upper part tight against the bag. What I found was that the bag did not have any air the next day. I believe that the rubber band prevents the bag from unraveling and thus sucking air in through the valve. I am sure that in the beginning co2 is an issue, but these beans were roasted 6 days ago and I have had the rubber band on for a few days already.

Image

Bag after removing the rubber band still very tight.


Pressino

#2: Post by Pressino »

I believe that the rubber band prevents the bag from unraveling and thus sucking air in through the valve.

I thought the purpose of the valve was to prevent air from entering the bag while allowing air to flow out of the bag, i.e. it's a one-way valve. If that's true it should not allow air to be sucked back into the bag. Unless the valve is malfunctioning, I'd guess the rubber band is just keeping the bag compressed and therefore keeping air from getting in via some other opening (e.g. the end of an opened bag).

Ken5 (original poster)
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#3: Post by Ken5 (original poster) »

Yes, I guess it could be coming in from the zip, but I usually find zips to be very dependable. I have heard some valves can be defective. Plus I 'think,' no expert here, that the main purpose of the valve is to let gases out. I sort of wonder how well it really works to keep air out. What I mean is it might take some reverse pressure to get the stopper to rest against the hole to prevent the air to get in? So a slight inward pressure caused by the bag relaxing might not create a tight enough closure of the valve to keep some air from getting it?

Either way, the bag is super tight against the beans when taking the rubber band off. Personally seems better than using my Airscape.

Nunas
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#4: Post by Nunas »

Pressino wrote:I believe that the rubber band prevents the bag from unraveling and thus sucking air in through the valve. I thought the purpose of the valve was to prevent air from entering the bag while allowing air to flow out of the bag, i.e. it's a one-way valve. If that's true it should not allow air to be sucked back into the bag. Unless the valve is malfunctioning, I'd guess the rubber band is just keeping the bag compressed and therefore keeping air from getting in via some other opening (e.g. the end of an opened bag).
I've tested quite a number of so-called one way coffee bag valves. My test is simple, fill the bag with beans, seal it, suck the air out via the one way valve until the bag looks like those vacuum-packed packages one sees in the stores (using a small vacuum cleaner)--wait. I didn't keep a scientific record of the results, but, frankly, none was needed. In nearly all the cases, air begun to enter the bags, almost immediately. I conclude that most one way valve bags are not much better than a regular bag with a pinhole. The so-called valves are probably there to avoid bags inflating in the stores as the coffee ages, not to keep air out--it's a bit of Madison Avenue advertising. So, I posit that the OP's rubber band idea, must at least to some extent, reduce air intake.

But, that does present a related head-scratcher about which I've got no clue. How is it that vacuum-packed coffee bags in the stores retain that sucked-in, hard as a brick, look, seemingly indefinitely :wink: ?

Ken5 (original poster)
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#5: Post by Ken5 (original poster) »

Thanks Maurice!

I wonder about those vacuum packed bags myself. Actually one time I got an order with 3 bags of coffee from the west coast and it got here in just 2 days from roast date. When I opened the box one bag was as tight as those vacuum packed bags. Roaster said they do not vacuum pack their bags and probably had something to do with it being on a plane. If so it was the one time a one way valve actually worked both ways! Bag stayed compressed till I opened it which I thought was weird in itself since it was just roasted. I was puzzled why the bag did not soften up from off gassing.

These bags that I just ordered are not getting any bigger with the rubber bands on them. Wonder how long it takes for beans to stop off gassing. Perhaps one explanation for them not bloating the bag a little is that the co2 is still making its way out the valve, though I wrap the bag back over the valve, not that that would stop it. I would think though that there would be some air left in bag even if some makes its way out the valve. Perhaps putting the bag with rubber band in an outer plastic bag to see if that takes on air is my next step to satisfy my curiosity.