Fixing Visible Folds in Theater Screen

[Frank Cox]

Maybe a hair dryer would work with less chance of overheating something since you're not playing with as much power as a heat gun.

[Randy Stankey]

I agree except for one thing... Regular hair dryers don't have temperature control.

I suppose you could start with its lowest setting, though.

Mark, you're right. You've got to watch your distance!

Luckily, the heat guns I use have temperature control where the sensor is just inside the nozzle. In other words the maximum temperature you can get is what it says on the display. If the gun is farther away from the workpiece you won't get that temperature unless you hold the gun steady for some period of time.

[Ryan Gallagher]

If you were after finer temp control, a hot air rework station can be dialed in by degree (and also senses temp at the nozzle). But the largest nozzles are not very large, and a bit unwieldy in a man lift or on scaffolding.

still quite dangerous, cause the metal nozzles will likely reach a higher temp than the airflow. I’d be tempted to make a silicon nozzle extension (regardless of gun type) that won’t conduct that heat as well in an abundance of caution.

can also check your air temps with a multimeter probe and watch the screen temp with an IR laser if unsure of your control.

[Randy Stankey]

Those Steinel guns we use can be set from 120º F. to 1,200º F. in ten degree increments.
That's plenty enough temperature control for the task at-hand.

If you have a diffuser attachment for your gun, I suggest using that.

I agree. If you don't have a temperature controlled heat gun, some kind of temperature sensor like an IR probe (or better, a FLIR) would be a smart idea.

[Marco Giustini]

I'd definitely ask the manufacturer for advice but what I'd do is increase the tension and turn on the heating (at higher than usual) for a few hours, then increase the tension again.

[Mark Gulbrandsen]

I'd definitely ask the manufacturer for advice but what I'd do is increase the tension and turn on the heating (at higher than usual) for a few hours, then increase the tension again.

And 30 plus years ago that's exactly what I did for a customer in Wisconsin... They first said the screens stayed in the boxes too long, but to turn the heat up another ten degrees at night for a while and see if it helps. I can honestly answer that it really didn't. It was not possible to increase the tension either, as these were old style wrap around frames. Anyway, during the 16 years I was a dealer, I never had screens shipped in boxes.

[Marco Giustini]

I am not familiar with the "wrap around frames" - the ones I have in mind do wrap around but you can still apply some tension?

Is the "fold" an actual, physical material deformation or is it the material which has degraded and now reflects differently than the rest of the screen? You can check with lights low/down and a flashlight, shining light at a steep angle. 'Cause if it's the material which has changed its property, well that's end of the line.

[Marcel Birgelen]

My experience, with a vinyl-type screen if those folds are deep enough, you'll not get them out of there with just stretching, at least not without risking to over-stretch the material.

Assuming that the movie screen is made of Polyvinyl Chloride (PVC) or at least something similar:

According to Wikipedia, PVC melts at temperatures between approx. 100º C and 260º C. (depending on its exact composition and form) and it's transition temperature (the temp. where it begins to melt) is around 80º C. (175º F.)

If I was doing this job, I'd start out with my heat gun set at a temperature as low as I could set the gun for and work up. The heat guns where I work can go as low as 120º F and as high as 1,200º F. I'd start at 120º and work up to 150º but I'd be hesitant to go above that.

I'm not sure if the plastic is really PVC based. A lot of stuff that's called "vinyl" doesn't contain PVC nowadays. While PVC is pretty fire-resistant for a plastic, the problem is that at high temperatures, it releases chlorine, which becomes rather deadly rather fast.

Also, modern plastics contain a large mixture of compounds, all with their own melting and color-changing characteristics due to temperature. I guess to be on the safe side, you need to perform some tests on some sample material. In this case, the original screen was much larger than the one it was used as a replacement for. So, they had some material to work and test with.

[Ryan Gallagher]

There are also the different materials/coatings that produce the various gain values to worry about, which might react poorly to direct heating. So if doing any heat gunning, the backside would be preferred if accessible.

The room air heating and re-stretching while it is warm is certainly the safest first attempt.

[Randy Stankey]

I'm not sure if the plastic is really PVC based.

I'm not sure that it's PVC, either. I just assume so because, even if it's not, it ought to be something similar that has similar temperature characteristics... Low temperature, relatively speaking.

Regardless what the material actually is, the smart money would be on starting at a low heat and gradually increasing until you get to a temperature that works the way you want. Test your process in an inconspicuous area like a hidden corner until you are confident that it works.

When I bought the screen at Mercyhurst, we got a swatch book of several different screen materials to choose from. If you have a swatch of screen material, it would be smart to test your process on that before you go blowing heat on your actual screen. You might be able to call the manufacturer and get one.

As others have said, you can also call the manufacturer and ask for advice while you are at it.

[Jeremy Weigel]

What about trying a fabric steamer to release the crease? I know upholsters use it on vinyl and leather. If I were to try it, I'd do it from the back side as to lessen risk of discoloring the matte finish.

[Ryan Gallagher]

What about trying a fabric steamer to release the crease? I know upholsters use it on vinyl and leather. If I were to try it, I'd do it from the back side as to lessen risk of discoloring the matte finish.

I would expect the heat from the steamer to be the ingredient that does anything on vinyl (since it is relatively impervious to moisture). I'd worry a bit about droplets forming and streaking in the "dust" if the screen was not brand new, being perforated, even back side may not be safe in that regard. Steaming is certainly safer than an iron on such materials... but the moisture may be the concern for a screen?

For fabric theatre drops and flats we just spritz cold water on them with a hudson, the fabric weave tightens as it dries... but I would not expect that technique to translate to PVC and related materials. ;-)

[Randy Stankey]

Don’t forget that the maximum temperatures that vinyl can withstand are between 175 deg.F and 200 deg. F. Steam is 212 deg.

When vinyl, plastic or whatever the screen is made from gets to its transition temperature it will deform and stretch. If the screen is under tension it will stretch as it hits transition temperature and, if it gets too hot, you might be left with a hole in the middle of your screen.