Film-Tech Forum ARCHIVE: Purple Dust?

This is topic Purple 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=006179

Posted by Craig Kocher (Member # 2432) on 05-16-2004, 12:26 PM:

hello everyone, This being my first Post I'll introduce myself. My Name is Craig. About 3 Months ago I became a Projectionist by Default when I became a Manager at my Theater. Thats not a Bad thing, Its one of the reasons I wanted the Job. I always wanted to do this sort of thing, I'm quite good at Projecting, Framing and all, but I dont know many technical things, but I'm willing to learn. In a few months my Company will be teaching me more and certifying me, but I Figured I'd probably learn alot on here.

So, I have a few questions...

Recently, I Noticed some Purple Dust coming off one of my Christie Projectors (we have 10 of them in the building) after the film is over. Any Idea what would cause this? its kinda clumpy and powder like.

Also, I Noticed the Flaking during my First Reel of Kill Bill Vol 2, what are the odds of this happening to other Black and white reels of films in the future? is this common? should I expect this with My Prints of Van Helsing that we have?

Thanks a Bunch.

Craig

Posted by Randy Stankey (Member # 64) on 05-16-2004, 01:09 PM:

Purple dust is a "feature" of Christie projectors. It's a special signal to let the operator know it's time to clean the projector!

[Wink]

Seriously... Christie projectors are pretty well known for this. It comes from the film gate abrading the emulsion off the film. By itself, purple dust doesn't signal a problem, per se. It's just the way Christie projectors are built.

Not to say that you should ignore purple dust building up on your projector. What is now purple dust USED to be film! Double check your film gate. (The two metal "straps", the two metal lateral guide wheels, the flip-open "shoe" and their associated film-bearing parts.) Make sure everything is properly aligned and there are no nicks or scratches on them. Any rough spot will act as a cutter that will literally scrape the surface of the film, producing your dust.

Do the same checks on the intermittent pad shoe. (The flip-open runners that hold the film onto the intermittent sprocket.) Same goes for all your sprockets and pad rollers.

Like I said, there's a certain amount of this that is to be expected when you have Christie projectors. If it doesn't get worse or seem to be damaging the film in a major way don't worry too much. I suggest you call your theater technician and see what his opinion is. I bet he'll say pretty much the same thing.

Here's the thing: Christie projectors must be kept scrupulously clean for them to work properly! If that dust gets too thick the projected image will start to get all jittery and unstable. The projector will give you all kinds of trouble. Yes, all projectors should be cleaned well but Christie's are more sensitive to dirt. Take your average Simplex or Century projector and run it for a couple of shows without cleaning it and it'll be mostly OK. Do the same thing on a Christie and you're begging for trouble!

When I was in charge of theaters with Christie projectors, my edict was to have every projectionist carry a cleaning cloth in their back pocket. Upon starting to thread a show, the projector was to be wiped out. (Alternately, a cleaning cloth can be placed on a shelf next to each macnine.)

Done regularly, this job takes less than a minute. (More like 30 seconds!) This simple task will save you all sorts of trouble in the future!

If you are going to be in charge of the booth I advise you to keep an eye out for the the famous Christie "Clean Me Signal". Any projectionist who works in your booth who leaves a shift without cleaning ALL projectors should receive an unfavorable review. It will take you only a minute or two to walk down the row and point out which projectors haven't been cleaned.

Posted by Craig Kocher (Member # 2432) on 05-16-2004, 01:32 PM:

Thank you very very much. Our tech always tends to have better things do to then to come to our theater. I appreciate all the help you guys will give me, its gonna take abit but I Really hope you all dont minds the 100's of questions I'm sure I'm gonna be asking you all.

Any Thoughts on the B&W flaking?

Thanks

Craig

Posted by Brad Miller (Member # 2) on 05-16-2004, 01:40 PM:

B&W will always shed more than color stock. As long as you are using Christie projectors, you will have a continuing problem not only with shedding, but that shedding will cause dirt buildup on the prints (mostly noticeable around the splices), sooner or later it will become abrasive enough to scratch the picture and from the get-go you will be literally scraping off your Dolby digital and SDDS digital sound tracks. Christie projectors run fine and dandy without print damage if you use FilmGuard. Those that run the film dry will be shipping damaged prints back to the depot. It's a fact of life with their gate design.

Posted by Craig Kocher (Member # 2432) on 05-16-2004, 01:50 PM:

Thanks,

You the man.

Craig

Posted by Dean Kollet (Member # 1789) on 05-16-2004, 09:24 PM:

the first reel of Kill Bill Vol. 2 was B&W but it was printed on color stock. Wouldn't it act the same as Color film? We had 3 Prints orginally, and we did not have a single shedding problem...

Posted by Brad Miller (Member # 2) on 05-16-2004, 11:51 PM:

Some prints of Kill Bill have reel 1 printed on color stock, others are on black and white stock. With yours being on color stock, you won't notice any difference in shedding.

Posted by John Anastasio (Member # 607) on 05-18-2004, 06:39 AM:

I run a Christie P35C with a curved gate in my screening room and I make sure that the bands and the gate are cleaned after every showing, sometimes after every reel. If you let any buildup occur, it acts as an abrasive. FilmGuard does stop a lot of this. One thing that I can say is that, because of the swing-out design, it's easy to clean everything in a few seconds. I keep a cloth soaked in a little FilmGuard nearby to make the job easier. That stuff really wants to stick to those stainless bands. In a clinch, a fingernail works wonders. Wooden dental stimulators are good too, since they're soft enough not to scratch the metal.

Posted by Randy Stankey (Member # 64) on 05-18-2004, 01:36 PM:

quote: John Anastasio

In a clinch, a fingernail works wonders. Wooden dental stimulators are good too, since they're soft enough not to scratch the metal.

A guitar pick works well. It's made of plastic and it's got just the right shape to get into the corners, etc.

If your state lottery has "Scratcher" tickets. (What state doesn't!?) You may be able to get your hands on a few of those little Good Luck Charms that they give away to scratch the tickets with.

Either way, just use care so that you don't damage any parts of the gate.

No matter what, if you have Christie projectors, the number one most important thing you must do to keep them running right is to keep them CLEAN!

The second most important thing is to check those belts religiously!

Posted by Brad Miller (Member # 2) on 05-18-2004, 04:23 PM:

Forget fingernails and guitar picks. If there is any hard residue in the gate after a show, you have just caused damage on that print's last run. After running Christie projectors for a number of years, I'd say if I wiped them out once a week, that was plenty...and I NEVER had hard deposits on the bands. Run the FG on your prints and the problem will go away.

Posted by John Anastasio (Member # 607) on 05-18-2004, 06:20 PM:

I run FG on all my prints using an attic-mounted web cleaner, but I also clean the heck outta that Christie. Most of the problem is on older prints that have only run through the cleaner for the first time. Those tension bands are so polished that you could use them for mirrors, but you can't avoid a little buildup now and then, so I just automatically clean them before each threading. I actually ran a film a couple of months ago that shed so much that it built up enough crud on the cleaner web itself (soaked in FG, of course) to make it stick on one side before it even got to the feed sprocket. I've never seen film shed like that. I had to stop the machine and advance the cleaning media by hand to a nice, clean spot so the film wouldn't be scratched.

I used to make guitar picks out of my old credit cards, but considering the level of my playing, Randy's now given me a better use for them. [thumbsup]