Film-Tech Forum ARCHIVE: Film bubbles

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Posted by Eric Nirome (Member # 5091) on 01-29-2009, 01:49 AM:

Hi, I'm Eric and I'm sort of new to projection. I've been working at a theater in Wichita, KS since June. And I've been in projection since October. They were going to make me Head Projectionist, but a spot opened up in management just last week. But even as a manager, I still deal with a lot of projection.

Now, for the past few weeks I've noticed a problem with one of our movies, The Tale of Desperaux. (sorry for the poor spelling) It always wrapped very tight on the tapeup, and it causes a bubble to form when removing the ring. Now, originally I thought it was a problem with the SPECO 270 in auditorium 13 since the platter was moving slow as the movie played. But we moved the movie to auditorium 2, and the same problem occurs. Now here's where it gets interesting. Auditorium 2 is a split screen with The Tale of Desperaux and Bolt, and Bolt's takeup is just fine. Does anyone know what could possibly cause this to happen?

Posted by James Westbrook (Member # 3690) on 01-29-2009, 02:58 AM:

Try swapping out the platter rings.

Posted by John Wilson (Member # 269) on 01-29-2009, 03:14 AM:

When you say it bubbles, do you mean it rises up around the ring as it gets more film on the plate?

Posted by Monte L Fullmer (Member # 2797) on 01-29-2009, 05:07 AM:

Welcome to Film-Tech! Pull up a chair, sit by the fire and enjoy the warmth!

It's when the ring gets pulled, the leader and first sections of film suddenly collapses inward towards the center creating a 'wave of film' of sorts - due to excessive cinching of the film on the inital rewind of the platter.

If you wind soundtrack down, do a wind soundtrack up on the ring since the film has a natural curl to it and it could be fighting with you or against you to wind smoothly.

It also could mean a "green print" that isn't 'seasoned' properly and they love to wind tighter than some other prints.

For, once in a while, I get the same results on certain prints..with my STRONG platters..

-Monte

Posted by Randy Stankey (Member # 64) on 01-29-2009, 09:17 AM:

Does it look anything like this?

You might have print damage due to somebody misthreading the projector. That's what happened in this picture.

If that's what happened to you there will be no way to completely solve the problem without replacing the print.

Like Monte said, you can try to run the film with the soundtrack down on the platter for a while. Bending the film the other way might flatten it out.

You can also break the film down onto 6,000 ft. reels and rewind it back and forth a few times then build it back onto the platter.

Neither of these methods are a cure. They are only to get you by.

If your film is not damaged there might be a problem in the platter causing it to wind to tight. Monte alluded to this too.

Can you describe the problem in detail or can you get us a picture? That would go a long way. [Smile]

Posted by Dave Macaulay (Member # 813) on 01-31-2009, 11:32 AM:

Sometimes a print just does this. I think it's a coating issue, the prints are "waxed" (as far as I know) so they slip through the gate smoothly. If the coating is extra slippery then the coils on the platter wind up tighter than normal during takeup, and when you pop the ring you get those bubbles or lumps when the pressure relieves itself.
As long as the lumps don't hit the payout it shouldn't be a problem during a show, the platter may speed/slow every turn but that won't cause problems with most platters - some designs have enough motor torque that the whole print disc shifts or (ouch) gets tossed on the floor though!

Posted by Richard B. Perrine (Member # 409) on 01-31-2009, 11:35 PM:

Tell you this one.....after having our theater closed for a year
(the owner had rented it for several previous years)...I went in the power everything back up and start running again.
The LP-270 wrapped the film thight on all levels used for take-up. The film popped the "bubble" in when I removed the ring.
It never did it before in all the years of running. The ring was difficuilt to remove too.
What I discovered was that the roller ws sticking...the one at the top of the twisted rod. Taking it off the shaft, cleaning it and some lube fixed the problem.
This doesn't explain why you have the problem with only one print.

Posted by Dan Reiter (Member # 1386) on 02-02-2009, 09:32 AM:

I see it as a combination of two problems.

One is definitely the print, since a different print on the same platter has no problems. Remember those horrifying days of "American President"? Does your platter have a film-wrap tension sensor system? Look at that too.

Second could indeed be a tight roller on the platter causing a tight wrap. Make sure all rollers operate freely.