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Author Topic: Theatre Temperature John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 03-23-2003 08:03 PM                        The ideal range for film projection and handling is between 50 and 60 percent RH. Really low humidity will cause excessive "positive" curl and increased static charging. Very high humidity will cause "negative" curl, and the moisture softens the gelatin emulsion, making it stickier and more likely to be abraded. High humidity is also likely to cause rust and corrosion of equipment.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 03-23-2003 08:21 PM                     Considering that cinesphere sits in lake ontario one would think low humidity would not be an issue but even in the summer it is lucky to get the booth up to 40%  |  IP: Logged William Leland III Master Film Handler Posts: 336 From: Charleston, SC, Registered: Aug 2002 posted 03-24-2003 10:25 AM                        Aaron Mehocic, during the winter months our humidiy reading was in the low 20's. We do have a humidifier and I saw no help. The film would still stick. I am assuming your are running 35mm film? I have never found a way not to keep a print from sticking once the humidity is out of the control area. Film Guard does help. Mr.Pytlak what do you mean by an "excessive positive curl" do you mean the film will actually curl? During the winter months our film was concaving. It ran fine but from the QTRU to the projector the film was "curving" down towards the floor. Is this what you are referring to as "excessive positive curl" .?  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 03-24-2003 01:26 PM                        Yes. With very low humidity, the gelatin emulsion loses moisture and shrinks relative to the polyester base, so it pulls in and causes "positive" curl. With very high humidity, it expands with the added moisture, and curls the other way -- "negative curl". It's all described on the Kodak website: http://www.kodak.com/country/US/en/motion/support/h1/baseP.shtml A quick way to judge the proper humidity is to hang up a short strip of film --- it should hang with just a slight amount of "positive curl". If the curl of the film is more than a few millimetres across the 70mm width, use a humidifier to get to the ideal range of 50 to 60 percent RH.  |  IP: Logged Aaron Mehocic Jedi Master Film Handler Posts: 804 From: New Castle, PA, USA Registered: Jun 99 posted 03-24-2003 02:10 PM                     William, Yes, I'm running 35 mm. Not all humidifiers are created equal. Sears Kenmore builds about the best I've seen and I hardly ever use it for already mentioned reasons. NEVER NEVER NEVER use a humidifier that sprays water directly into the air (I know you know that, but for the popcorn poppers out there that might just care enough to visit this site.)  |  IP: Logged William Leland III Master Film Handler Posts: 336 From: Charleston, SC, Registered: Aug 2002 posted 03-24-2003 02:33 PM                        Mr.Pytlak thanks, that site is very helpful.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 03-24-2003 02:37 PM                        The most efficient humidifiers blow air through a foam, paper, or ceramic material that is saturated with water, and the water evaporates into the air. They are sometimes called "whole house" humidifiers, or "Wick, evaporative" humidifiers: http://home.howstuffworks.com/humidifier4.htm http://home.howstuffworks.com/humidifier1.htm Steam vaporizers actually boil the water to form steam, which uses alot of electricity. The hot steam can also cause burns. Ultrasonic or impeller humidifiers that actually spray or mist the water into the air are NOT recommended. The mist may actually get things it touches wet (not good for film or electronics), and carries all the minerals that were in the water, so that when it evaporates, it will leave behind mineral deposits (also not good for film or electronics). Do NOT use a "cold mist" impeller or ultrasonic humidifier in a projection room. Here is an example of an evaporative "whole house" humidifier: http://www.allergybuyersclubshopping.com/bemis-h12-300.html  |  IP: Logged Lance C. McFetridge Expert Film Handler Posts: 135 From: Penn Yan, New York Registered: Jul 99 posted 03-25-2003 10:23 AM                     Each of my auditoriums has a remote reader that samples the temperature at about 6' off of the lowest floor height. This remote sends the temp to the thermostat located in the booth. We find that 74 in the winter and summer is just right for comfort. Each auditorium has it's own HVAC rooftop unit. I also put a remote in the lobby with the thermostat in the storage area so no one messes with it. lance  |  IP: Logged William Leland III Master Film Handler Posts: 336 From: Charleston, SC, Registered: Aug 2002 posted 03-25-2003 03:45 PM                        Lance, what type of remote reader do you have? Who makes it? Was it installed by the builders or was an after thought? Does it work well? Thanks Will  |  IP: Logged Lance C. McFetridge Expert Film Handler Posts: 135 From: Penn Yan, New York Registered: Jul 99 posted 03-25-2003 06:36 PM                     Will, Both the thermostats and remotes are manufactured by Trane. I have had them in from day one and they do work well. You can calibrate them if needed and are simply attached through a low voltage thermostat wire. I will check for the model number tomorrow. Hope this helps, lance  |  IP: Logged

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