Canned gas

[Bill, 70's military B&W]

I know that many use the cans for blowing dust off negatives and other house cleaning purposes, but does anyone use the cans of pressurized gas to displace regular air?
When you open up a chemical, it has a shelf life of only a few months, does displacing the air (oxygen) with a spray of ethylene chloride (if I remember right) prolong the shelf life of the chemical?
Is there any combination that I should avoid? I know to keep the can upright.

[lenser]

I remember buying cans of Nitrogen (I think, or some other inert gas) for just that purpose at the local camera store. Don't know if it's still around or not.

[Jeff Bannow]

There are products for topping off bottles of wine. That should work, although I don't know how expensive it is.

[Jim C.]

What you're looking for is blanketing gas, I use them to protect moisture sensitive materials I use.
There's specific kinds of blanketing gas, one is flurocarbon based the other is inert gases.
Problem with the flurocarbon types is that they tend to contract so the container will suck in slightly, not good if you intend
to store stuff for along time as the containers may rupture, not dangerous but can be messy.

Bloxygen is an inert gas blend - http://www.bloxygen.com/purch.html

flurocarbon based
Xtend-it - http://www.smooth-on.com/Urethane-Ru...203/index.html
Burp -http://www.anchorseal.com/miscProducts.html

The last option would be to get a small inert gas tank and have it filled at a welding gas supplier with dry nitrogen.

[E. von Hoegh]

Or argon, as used in TIG welding.

[wallrat]

Bill, I use the Air-Evac Bottles. Freestyle sells their own version under the Arista name and there is another brand name that sells larger bottles (up to 2 gallons). They are great for keeping chemicals fresh as once you are done with the chemical, you smash the bottle down and cap it when the chemical is even with the top of the bottle and then you eliminate the issue with air in the bottle and it's far more reusable, less expensive, and more ecologically friendly than using air replacement techniques. My chemicals last forever (not literally). I have a bottle of rapid fixer in a black 2 quart air-evac bottle that is going on 9 month old and it still fixes great and passes the fix test. I don't use the Illford all the time, but the fact that it's lived that long is a testament to these bottles effectiveness.

[Bill, 70's military B&W]

Thanks, wallrat and everyone, I just placed an order with Freestyle for the evacuation bottles. For the smaller bottles I use the ethylene chloride that is commonly found at Computer stores for blowing away dust. I just spray a small amount into the neck of the bottle and put the lid on. I'm not getting all the Oxygen out but I am reducing it. I just hope there is not a chemical reaction that I am not aware of. The evacuation bottles were not expensive and will do a much better job, I'm sure.

[Ian Gordon Bilson]

Bill,the compressible bottles have a poor reputation,as a Web search will reveal. The flexible plastic is the wrong type for chemical storage and is oxygen-permeable.
Which kind of defeats the intended purpose..
Ordinary Butane gas will do the job - the refill cans for barbeque lighters.I keep a small gas torch handy - a decent puff into the bottle will blanket the chemistry nicely.
No ignition sources,for obvious reasons.

[wallrat]

I was told by freestyle that the makeup was changed some time ago to fix that issue. I have seen zero issues with over 2 years of using them.

[Bill, 70's military B&W]

Well, I have some collapsible bottles coming from Freestyle, and I will also be using the 1 gal plastic bottle that the distilled water comes in. As far as cleaning the collapsible bottles, I think I'll keep them dedicated to a specific chemical and cleaning should not be all that problematic. I hope wallrat is right and the bottles have been modified.

So far (a few weeks in my case) I'm using the compressed ethylene chloride from Best Buy at about $3.50 for a large can to displace the oxygen. It's cheap, no odor, should work! My only concern would be if there is some chemical process, some incompatibility I am unaware of, either with the chemicals or the plastic container. If there is a problem then as Ian said Butane is another alternative.

I was reading and someone said that stop bath and fixer are not sensitive to oxygen, so that gas displacement or evacuation bottles are not needed. Is that true?
Besides the developer what other chemicals do I need to be guarding against oxygen?

Thanks, Bill