O.K. Inspite of best efforts, disasters can happen...
A problem with my compressed gas (nitrogen) setup which I use to dust off film p rior to scanning left some small gobs of gunk on one of my transparencies. It a ppears to be an oily deposit. What is the best way to remove this gunk off of t he transparencies?
I've since found the source of the problem, and corrected it. It happened to be a bad regulator which my gas supplier gave me.
PEC-12
Sounds as if you need a hepafilter in your air line Larry.
Pete,
The problem was fixed without a filter. My gas supplier gave me a regulator when I got this nitrogen tank. Last week I went back to the gas dealer and we found the problem by switching out all the components one by one. The old regulator somehow ended up with gunk which mixed with the gas. Getting a new regulator solved the problem. Just a proof point in the saying that you get what you pay for. Now it works great, and it's wonderful having a huge dust-off can without the noise of a compressor.
I find it interesting that Larry uses a cylinder of nitrogen as a dusting device. I've thought of using my SCUBA cylinders, but never saw any kind of hose with a regulator and a blower on it that fits the standard non-DIN SCUBA fitting. It seems to me that the air would be much cheaper than nitrogen (assuming you have a place to pump it), and you wouldn't have the asphixiation scare.
I got the idea of nitrogen from the archieves which are part of this site. After the initial outlay for a tank + regulator (~$130), getting the tank refilled is *MUCH* less expensive than those Dust-Off cans which seem to have about a dozen good shots in them before the air pressure reduces to the point where the can isn't useful. You also don't run the risk of having that white ick (the propellant?) cover your stuff. I believe my tank is a 60 cubic ft tank, and it will cost less than $15 to refill. From what others have said, Nitrogen is one of the least expensive industrial gases, and is suppose to be very dry and clean. I wasn't aware that compressed Nitrogen was a significant health or safety risk.
Larry if that tank leaks in a closed room while you're around they may have to carry you away in a black bag. Normal air contains 21.5% oxygen - dilute that much below 18% with nitrogen and you might take a "dirt nap". 60 c.f. isn't much - but it can be enough.
While is is possible for a 60 cu. ft. tank to reduce the oxygen concentration in a small sealed room, the chances of it doing to without you noticing are pretty remote - it will have to leak fast enough to be heard. If your darkroom is sufficently ventilated to safely use processing chemicals it's almost certainly a non-issue.
The real problems with pressurised cylinders are that the neck can break off if they fall over or are dropped. They can explode in a fire: the local firemen tell me that of all the hazards in our labs, it's the gas bottles they fear the most. Transport carefully, chain in place for use, and evacuate to safety in any fire which gives you the option.
I don't have a lot of experience of removing stubborn stains from transparencies, but PEC-12 has always worked when simple re-washing failed.
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