Film-Tech Forum ARCHIVE: Wierd white dust

This is topic Wierd white dust in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=009040

Posted by Christopher Howland (Member # 4386) on 12-27-2007, 10:14 PM:

Hello everyone,

I have been having a strange problem with one of my projectors when running films lately. For some reason, there is a white dust that is coming off of the film and gets all over everything, the brain, the internals of the projector, etc. The picture area of the film is not affected, it does not seem to be damaged in any way. The first time i played it i thought someone had been a little happy when using some kind of china-mark at a different theater (we dont use china-mark or any other kind of marking on the film).

However, after cleaning it after every show, the white powder comes back. I film-guarded it, thinking that the film was shedding or something, but it didnt stop it. I then changed out films twice, and it still happened. Recently, another projector has began to do the same thing, although not the same extent. I checked all the rollers and looked over the internals of the projector, but i really dont know what to look for that would be causing it.

The projector and platter system that is creating the white dust is a Century SA with a Strong 3 platter system. I really am stumped. It's getting annoying to clean off EVERYTHING after every show. Help!

Thanks in advance,

Chris

Posted by Robert E. Allen (Member # 1351) on 12-27-2007, 10:55 PM:

I experienced the same thing at a Regal house I was working and was told that it is "polyester dust" from the print. It was usually eliminated by putting a film cleaner on that machine.

Posted by Monte L Fullmer (Member # 2797) on 12-27-2007, 11:27 PM:

SA's .. checked to see if the trap bands are okey and not scarred by any reason along with the gate rails?

Posted by Frank Angel (Member # 248) on 12-28-2007, 12:57 AM:

At first I would have suspected a print that was sliced just a tad badly....it happens. But you said you changed out the print twice; I take that to mean that the white particulate is present with different prints playing on that same machine, correct? If this is the case, then, even though you might not see what mechanical condition is causing it, it definately IS something mechanical in that projector system.

Can you determin where the dust is most concentrated? That is going to give you a clue as to what mechanical piece is rubbing and therefore sheering of minute particles of poly from the base. Also, examine the print very closely. Use a loupe or small magnifying glass -- I always keep an old 16mm 2in lens on the rewind table, makes a great very powerful magnifier. Look to see if on the base side of the film there is any scratching --it could be very minute and only visible under the magnifier and that is why it is not obvious to the naked eye. It will not be on the emulsion side because if it were, you would see it on the screen, big time.

If there is nothing at all visible in the way of scratches on the base side as you look at it under the glass, then it can very easily be some friction scrapeing the film on either edge. Sometimes that kind of scraping on the edge just can't be seen, but it can be felt. Run you finger along the edge. Does it feel rough or odd in any way? Compare it to another piece of film that hasn't been run thru the suspected machine. See if you can feel a difference. If you do, then it will be a matter of finding what part of the projector is scraping the edge of the film. And then back again to where the most powder seems to be accumulating, that will help you to look in the right area.

Let us know if you get any closer to solving it.

Oh yah, and PS -- best thing for that kind of shedding -- get a good vacuum cleaner in the booth -- one with a HEPA filter. It is much better than trying to manually dust that stuff away which will just spread it around. Until you find the cause, you really want to vacuum that stuff away from any moving parts.

Posted by Steve Guttag (Member # 268) on 12-28-2007, 08:17 AM:

I think Monte is probably close to the mark. Look in the gate/trap area. Tension bands, gate runners and intermittent shoes (oh my!) are the most common culprits of print shedding as the film must actually rub those parts.

Use of Film-Guard will also eliminate the shedding (if done properly by using a film cleaner on each show). It is still best to find and eliminate the source of the damage to begin with though.

Posted by Andy Bergstrom (Member # 360) on 12-28-2007, 09:22 AM:

What is the humidity in your booth? The winter months in your local must produce some very dry conditions in your booth. Do you experience any film wrapping or static problems also? If you don't discover a mechanical flaw in the projector, I would try raising the humidity in your booth. Be sure there isn't any heat ducts or lamp exhausts blowing on the platter further drying things out. Just something to check.

Thanks,
Andy

Posted by John Hawkinson (Member # 1135) on 12-28-2007, 10:09 AM:

Also, try running a loop of scrap film for several minutes and then examining the loop. If the film is getting damaged, the loop is likely to show it more clearly since it runs through the projector repeatedly (and at a higher temperature).

--jhawk

Posted by Christopher Howland (Member # 4386) on 12-28-2007, 06:57 PM:

thanks for the help everyone, ill be sure to check the tension bands and gate runners as well as the intermittent shoes.

I had 2 different movies playing in the suspect projector with the white dust, otherwise i would have looked more at the actual print rather than the mechanical side.

The humidity is not too bad in the booth, it normally gets pretty toasty up there, and we regularly prop open the outside door to the booth to let in the cold air. All of our projectors exhausts exit out to roof blowers, so they are not drying out the booth.

Although the humidity is fairly low here, we usually do not have problems with wrapping or static electricity. Our booths (we have 3) are tile and cement, so no static generation there. I regularly film-guard all the films, so that helps immensely too.

Posted by Ron Funderburg (Member # 4561) on 12-28-2007, 08:24 PM:

I would suspect that the "white dust" is fine metal or plastic shavings from either something on your projector or platter. I had the same thing happen on a DTS reader and the outside of the projector it was the sliver roller and the black roller rubbing together and the black roller was winning!

Other than that I don't know unless you have co-worker that is very careless with his personal use white dust!

Posted by Peter David Bruce (Member # 4447) on 01-02-2008, 07:08 PM:

I still get the white dust on some prints, but usually a buildup on the edges alone... not from the centre. FilmGuard has managed to remove this every time and since using it every 3-4 weeks on each print we have seen a dramatic decrease of 'snow' buildup... However I Am Legend (still in its first week of release) looks to need a clean ASAP!

those rollers look like christmas came and snowed! infact we might get snow tomorrow! [Smile]

Posted by Ron Funderburg (Member # 4561) on 01-02-2008, 08:11 PM:

Peter, there is still something causing the dust to happen that is the larger question here. The dust has to come from somewhere, a gate to tight, parts rubbing together, something is in need of adjustment that is what you need to find out where it is coming from and what is causing it!

Posted by David Zylstra (Member # 4230) on 01-02-2008, 09:18 PM:

Check to make sure all the platter rollers and keepers are spinning - on the ORC platters I worked with years ago we would sometimes see the guide rollers on the feed plate control arm stick, then the film would cut into the nylon and we would see similar dust to what you are describing - Strong had a similar roller setup on their control arm and maybe the issue is similar.