Film-Tech Forum ARCHIVE: Prints Shedding Blue/Purple Dust.

This is topic Prints Shedding Blue/Purple Dust. in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Frank Aston (Member # 478) on 08-11-2003, 02:21 AM:

Has anyone encountered this problem with certain UK release prints?

Bruce Almighty and Charlies Angels were particularly bad.

I've scrutinized all my line-ups, sprockets, gate pressure pads, xenon outputs etc but, in any case, the problem is not common to any particular machine.

Posted by Michael Brown (Member # 890) on 08-11-2003, 06:51 AM:

I've had it on the few occasion that I've had new prints.

Not sure what it is.

Posted by Frank Aston (Member # 478) on 08-11-2003, 10:31 AM:

Thanks Micheal. Have you noticed if it's common to any particular lab?

Posted by John Spooner (Member # 1565) on 08-11-2003, 11:58 AM:

Dear Frank and Micheal.
Your post is certainly timely as I am currently running Charlie`s Angels and the same coloured dust is occurring.
Noted it tonight especially on the inner roller of the hold-back sprocket. Assuming the roller could be misaligned I cleaned and reset it, however it may not be the roller seeing your same dust experience.
Due to the colour of the dust I assumed the edge of the roller or another guide could have been grazing the digital track on the film edge, but upon inspection the roller was correct and no sign of any grazing to the film stock.
I also had the same thing occur during "The Core", exactly the same coloured dust, but on another machine and the dust built up at the top of the gate runner.
A very unusual thing as we would agree.
John Spooner. South Australia.

Posted by John Pytlak (Member # 331) on 08-11-2003, 02:01 PM:

What is the full magenta edge-print ID of the reels affected? It could be either a stock issue, or a lab issue if the same problem is affecting multiple theatres. At the lab, the process machine drying conditions and whether they follow the Kodak processing specification for edge-waxing are pertinent to scuffing type emulsion debris.

Posted by John Spooner (Member # 1565) on 08-11-2003, 02:26 PM:

Dear John. Thank you for your reply both personally and on the forum.
I will be at the same theatre again tonight and will attempt to note the edge details.
From what I understand, most Australian copies are processed in Sydney by Atlab, will ask my management to ascertain from the distributors.
There has been no change in projector settings or ambient humidity.
Also the same thing occurred on some spools of "Ned Kelly", which was made in Australia and certainly would be Australian processing.
Best regards to you and Teeny Weeny.
John Spooner.

Posted by John Spooner (Member # 1565) on 08-12-2003, 11:18 AM:

Dear John.
Here are the edge nos for the 6 spools of Charlies Angels which is leaving the purple dust. Spools 4-6 are the worst.
spool 1. 2383 954 088 1 12 KODAK 22 2003 A
spool 2. 2383 954 088 1 16 KODAK 22 2003 R
Spool 3. 2383 954 008 1 30 KODAK 22 2003 U
Spool 4. 2383 954 088 1 34 KODAK 22 2003 J
Spool 5. 2384 954 089 1 00 KODAK 22 2003 Y
Spool 6. 2383 954 088 1 35 KODAK 22 2003 U
Best regards. John Spooner.

Posted by Bill Langfield (Member # 818) on 08-12-2003, 02:35 PM:

Hey John(s)

The 'purple dust' you mention has been around for as long as I can remember, it simply just turns up in certain prints no matter what lab made them or what film stock they used.

No one I know has ever documented it, perhaps we should start now.

We used to call it a 'green print'. (Not fully dried at the lab)

I have no idea what causes it, the film is never damaged as far as Ive seen.

But it gives you a damned good scare when you go to lace up the next show and see all that purple stuff on the intermittant sprocket and on the gate pressure pads. Straight away thing thinking you've missed theaded the last show. OUCH

When you get prints that do this, that junk, is erm, an easy way to determine if the projectionist the night before bothered cleaning the machine.

The only print Im having trouble with a the moment is T3, its leaving a (moderate) white dust on certain rollers, dont know what that is.

Bill.

Posted by Michael Brown (Member # 890) on 08-12-2003, 02:52 PM:

It seems to be something that happens with brand new prints.

I show 95% second run and it's never occured with those.

I've just had it happen about 3 or so times that I've had brand new prints for preview screenings.

Posted by John Pytlak (Member # 331) on 08-12-2003, 03:35 PM:

"Green" prints, fresh from the lab, may tend to leave more debris during the first few times through a projector.

First, the freshly processed and dried gelatin emulsion takes time to "harden". Time, and the first few times through a hot projector gate will harden and "polish" the surface of the film to better resist abrasion from the projector. Kodak processing specifications and SMPTE Recommended Practice RP151 both recommend application of edge wax or other lubrication after processing to reduce the frictional coefficient of the film surface and help resist scratches and abrasion.

Second, the gelatin emulsion swells with water in the processing solutions. Although it usually shrinks back to its original size when the film is dried after processing, sometimes the emulsion "hangs over" the film edges and perforations, and will get scuffed off during the first few projections, leaving a bit of dust and/or skivings. Today's on-line film cleaners are very effective in removing this debris so it doesn't show on the screen and before it may become embedded in the film.

Posted by Greg Routenburg (Member # 1742) on 08-13-2003, 01:06 AM:

Ah yes, this purple dust you speak of is quite common with most prints we run at our theatre. The trick is to keep it cleaned off because it seems to build up especially on the film runners in the gate and cause unnessicary friction which can't be good for the SDDS tracks. A simple utility cloth usually takes care of it. I'm constantly stuggling with the guys that thread at my theatre to stay on top of it but it's an ongoing battle.

Posted by Chris Hipp (Member # 1788) on 08-13-2003, 02:45 AM:

I usually notice this with new trailers and instituationals but never with a print.

The purple dust is quite common and usually builds up on the SDDS sprocket.

Posted by John Pytlak (Member # 331) on 08-13-2003, 06:05 AM:

FWIW, "Rolling stock" ads and "institutionals" are often printed on print film that is not made by Kodak.

Posted by Frank Aston (Member # 478) on 08-13-2003, 01:15 PM:

Many thanks for all the feedback. I think it's quite a serious problem because it's not long before the dust find its way on to the picture area with consequent image degrading.

And nothing seems to shift it.

Pirates of the Caribbean also seems to be affected.

Could it be anything to do with print quality control bearing in mind the massive print runs these days?

Regards,

Frank.

Posted by John Pytlak (Member # 331) on 08-13-2003, 01:57 PM:

quote:
Could it be anything to do with print quality control bearing in mind the massive print runs these days?

In my experience, it doesn't really have to do with the number of prints being made or how fast they are being printed. As others have noted, "green print" issues are not new, and fortunately theatres now have better methods of dealing with them by using on-line film cleaners.

The 75-year old Kodak publication "Film Mutilation and How To Prevent It" (that Brad just posted) talks about projector abrasion of prints film, and the importance of proper print lubrication and projector alignment in extending print life. The right way to do it doesn't change.

Posted by Chris Hipp (Member # 1788) on 08-13-2003, 05:58 PM:

Since we are on the topic:

Why is it that when I use a dry web media, the dirt is only on the media where the soundtracks are? I rarely see any dirt where the image is.

Posted by John Pytlak (Member # 331) on 08-13-2003, 10:04 PM:

quote:
Why is it that when I use a dry web media, the dirt is only on the media where the soundtracks are? I rarely see any dirt where the image is.

The projector components physically abrade the film along the edges and perforation area, so that is where debris is generated. Most good equipment designs hardly touch the image area, so abrasion is minimal there.

Posted by John Spooner (Member # 1565) on 08-14-2003, 12:39 PM:

Dear Frank, Micheal and John P.
John, the point about the emulsion hanging over the perf and film edges was of interest. Subsequently I adjusted the inner hold back roller so it was further away from the film edge and the dust build up was much less, almost no dust at the last screening. So the roller`s inner flange must have been grazing the emulsion overhang, this would tie in with the fact that there were numerous fine blue filaments with the dust and yet no visible sign of actual grazing as I previously stated.
Regards. John Spooner.

Posted by John Pytlak (Member # 331) on 08-14-2003, 12:42 PM:

Glad that the roller adjustment helped so much. [Smile]

Yes, "pinching" the edge of the print can cause skivings, especially with freshly processed "green" prints.

Posted by Michael Brown (Member # 890) on 08-14-2003, 12:48 PM:

a before e.

Michael.

[Smile]