Film-Tech Forum ARCHIVE: Question about heat tolerances for film stock

This is topic Question about heat tolerances for film stock in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Frank Angel (Member # 248) on 03-18-2003, 04:46 PM:

I know the easiest and most practical way to test the amount of heat the lamp, reflector and cooling assembly pumps into the aperture is to run B&W film that is totally black and to inspect whether or not the emulsion emerges unscathed, stressed, embossed or even blistered. But is there a temperature that is specifified by the manufacturer for each film stock, above which is unsafe for the emulsion. If so, then you could read the temperature with a temp meter and high temp probe placed in the gate -- you'd know without guessing how close you are to that tolerance -- you could read what you've got -- safe or not safe. It would be good to have manufactures specify that this stock should not be subjected to above xx degrees running at 24fps.

The reason this question came up is because there was a question about some damage on a B&W print and the client wanted to know if his projector was the cause or if it could have been damaged before it got to him. I suggested he run some B&W film with full black frames and on polyester stock as the film in question was on polyester, then observe the condition of the emulsion. Problem is, B&W on polyester it isn't exactly easy to find (anyone have enough to make a loop or two they can part with?). It occurred to me that if you knew a specific figure in degrees that any particular stock could tolerate, you could do a test without the film. I mean to me, it seems that checking for the safety of lamphouse heat intensity by running the film and checking visually for damage is about as scientific as aligning the B chain by running film and checking the levels by listening.

Frank

Posted by Gordon Bachlund (Member # 124) on 03-18-2003, 06:21 PM:

Frank, you can get black frameline leader at www.ntaudio.com/1leader.html where it is sold by the 100' roll and also by the foot.

Posted by Scott Norwood (Member # 30) on 03-19-2003, 06:30 PM:

By law in Massachusetts, the temperature at the aperture cannot exceed 800 degrees. I have no idea where they got that number, but it must have had something to do with the flammability characteristics of nitrate-base film.

Posted by Gordon McLeod (Member # 33) on 03-20-2003, 01:55 PM:

get a thermal couple probe and place it in the trap assembly and get a read out of the temp

Posted by John Pytlak (Member # 331) on 03-22-2003, 06:17 AM:

Heat Damage:

http://www.kodak.com/US/en/motion/newsletters/pytlak/fall97.shtml

http://www.kodak.com/US/en/motion/newsletters/pytlak/winter97.shtml

Most of the radiant energy is absorbed within the thin emulsion layer, and the heat then spreads to the base. Higher densities absorb more energy. Silver images absorb infrared energy, whereas dye images are relatively transparent to infrared.

Running a loop of film with maximum (black) density is a good way to be sure you do not have excessive radiant energy that might cause heat damage after a few hundred runs.