I applaud the use of CO2 to blow out projectors instead of a compressor because of the moisture and oil that is contained in the stream of air. At least CO2 is a source of "dry air".

On the other hand, I don't recommend the use of compressed air (or anything like that) for cleaning out projectors on a regular basis. If you want to use it for the occasional "super-duper cleaning" I would aquiesce but that's as far as I go.

It seems to me that it can take longer to clean out the projector with an air gun than it would with a clean paint brush and a rag. There's overhead involved with lugging around a 20 lb. tank of "air". You can carry around a paintbrush and a rag in your back pocket. When you travel that light you can give all your projectors a right-fine cleaning each and every time you thread the film!

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The same situation with CO2 will cause extreme distress well before a blackout. I, for one, would seek an exit or fresh air at the discomfort stage.

Regardless, using a tank or compressor in the booth is a bad idea.
For dusting, it just moves the dust around both creating a never ending dust problem (it never goes away, just moves around) and coating your platters of film with dust. Vacuuming or wiping is the solution to dust.
For anything else in a projection room - with very few exceptions - it is ineffective, potentially damaging to equipment, and/or dangerous to the staff.
Blowing dust off lamphouse mirrors before cleaning is one job I would suggest a dust-off can or CO2 bottle for. A compressor will often throw a lot of oil and water with the air - not good.

I found that if I crushed the blocks into powder I got a better fog. So opening night, little did I know, that I put five feet of fog on the stage, engulfing our hunched over scrooge and nearly choking him to death. The first row of people also were choking rather heavily.

Scrooge was and still is played by the director of the show. After the show, he pulled me aside and said "young man, i thank you for the authentic london fog, however, please try to bring it to a more utah mormon level".

The next night the fog failed completely.

My point, yes, you can probably kill someone with that co2, I wouldnt use it. If you want to use compressed air, there is a new system out that you use the same cans over and it has a small compressor that you hook the can up to. It filters out all the impurities and gives you a nice dry air blow. You can find them at most office supply or computer supply houses.

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You can pressurize it with air but when the keg starts getting below, say, half full the air starts replacing the CO2 and making it turn skunky. This is why when you go to a party and the keg is tapped with one of those air pumps the beer starts getting "icky" the lower the level gets... Especially when the keg isn't used up quickly. With the general quality of most commercial American beers, it's pretty icky to begin with. Skunky low-quality beer is even worse.

There are two ways of carbonating beer. The "traditional" method is bottle conditioning, or krausening.

When you brew beer, you basically make a malt-sugar water solution, and add hops, and yeast, then put the solution, or "wort", into a glass carboy with an airlock. The yeast consumes the sugars, and excretes alcohol and CO2. The CO2 escapes through the airlock.

As the yeast consume the sugars, the alcohol increases, and the sugar decreases. Once the fermentation reaches a certain point, the yeast can no longer grow, and become dormant and settle to the bottom of the fermenting tank. The homebrew "standard batch size" is five gallons, because that's the size of the big glass carboys used for fermentation. Once the fermentation completes, the result is a five gallon bottle of finished, but completely uncarbonated beer, with a large mass of yeast on the bottom. The beer is siphoned from one carboy to another, leaving the yeast sediment behind.

This is how all brewing is done. Whether you're Anheiser Busch, or a homebrewer, at this point in the brewing process, you have a large container of finished, but uncarbonated beer.

If you're going to bottle-condition, or krausen the beer, the procedure is to boil a small amount of malt extract (to sterilize it), and add it to the beer right before you bottle it. What happens is that inside the sealed bottle, the remaining small amount of yeast floating in the beer detect the extra sugar, and revive and start to metabolize and reproduce. As the yeast consumes the extra sugar, it produces more alcohol, and CO2. This time, however, the bottle is sealed, and the CO2 doesn't escape -- instead it dissolves into the beer. In a few days, the small amount of newly produced yeast goes dormant, and settles to the bottom of each bottle. The result is a small amount of sediment in each bottle, and natural carbonation.

If you're just starting to homebrew, bottling is part of the learning experience, but once you've been doing it for a while, bottling becomes the biggest royal pain in the neck. First off, you need to get some 48 bottles absolutely clean, or you'll have random bottles of bad tasting beer. Second, you have to get the amount of additional malt extract just right. Too little, and the beer will be flat. Too much, and the beer will be either too fizzy, or even worse, the bottles will spontaneously explode in storage. Plus, making beer is an exercise in kitchen-microbiology and the art of keeping things sterile. The more steps you carry out, the greater the likelyhood of bacterial contamination, which causes off-tastes.

However, there is an easier and better way. Instead of bottling the beer, you use a 5 gallon stainless steel cornelius keg -- a soda-fountain keg -- what they used to supply soft drink syrup in before they switched to boxes. Of course, the keg must be completely cleaned out of any syrup residue and the gasket replaced.

To force-carbonate, you pour the entire five gallon batch of finished, flat beer into the keg, then connect a CO2 tank to the pressure fitting, set the pressure to 40PSI, and vigorously shake the keg. The beer absorbs CO2 so fast you can hear the valve hiss with each shake. After about one minute of vigorous shaking, the beer is fully carbonated. All you need do is remove the pressure hose, and let the keg sit for an hour or so. Then, you vent the pressure from the keg, hook up the CO2 tank to the keg with the pressure set very low -- just enough to keep the beer flowing, and connect a tapper to the keg. Then you tap and enjoy.

Force carbonation is a huge time-saver. It gets you the exact same results as bottle-conditioning with none of the work. Kegs are better at parties anyway, and the beer will stay fresh, because as you dispense the beer, you replace it with CO2 -- no oxygen gets into the keg, so the beer doesn't go bad.

The result is a more predictable brewing process, and in general, better beer. Force carbonation removes a whole set of variables in the process. There is absolutely no quality difference whatsoever between beer with CO2 generated by bottle conditioning, and beer carbonated with CO2 pumped in from a tank.

1. 85psi or 90psi for cleaning can still be quite dangerous. In the US, OSHA limits air pressure for cleaning purposes to 30psi. Specifically, 29 CFR 1910.242(b) says

quote:

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Compressed air used for cleaning. Compressed air shall not be used for cleaning purposes except where reduced to less than 30 p.s.i and then only with effective chip guarding and personal protective equipment.

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2. On the other hand, DTS recommends the use of compressed air to clean their timecode readers. Page 17 of the DTS-6D manual: "The timecode reader lens should be blown off with compressed air once a day to remove any dust build up."

This thread seems oddly timely; we're just looking at installing compressed air in our principal booth to avoid going through those Dust-off(tm) -type cans. Of course, it's a little differenct since there's already a compressed air plant in the building... We only use air for the DTS readers and for parts of our projectors that are hard to reach by hand...definitely no substitute for cleaning with a alcohol, a toothbrush, and a Webril wipe.

--jhawk

I do think that pressure washers tend to be used at much greater distances (tens of feet) than compressed air (inches), so I would expect a lot more risk to the eyes from air than water.