# Properties of Gel

#### Jankers

##### Member
Hey, quick question here:

Would regular gel be considered a plastic? I ask because I need to find a proper glue to adhere gel to a high temperature metal, in a situation that hot glue is not appropriate for.

Cheers!

James

#### JD

##### Well-Known Member
Modern "gel" is plastic (except diachronics), however some gels have the pigment on the outside as a coating, others are impregnated. Because of this it may not react to glue the way you would hope.

Jankers

Thank you kindly

#### Footer

##### Senior Team
Senior Team
Gel is 2 polyester layers with a color additive in between. Keith will be here shortly I would assume.

Last edited:

#### Kelite

##### Well-Known Member
Apollo and Lee gel are double coated polyester for color consistancy, while Rosco and GAM are dyed polyester. The Lee HT consists of polycarbonate material, which has a higher resistance to warping and color migration.

(Edit- Wow Footer, you know when I sit down and open the 'Booth, now don't you?!)

Last edited:

#### stantonsound

##### Active Member
ok....I love Apollo gel (and most Apollo products - I use scrollers, rotators, gel, gobos, and more), but recently needed a few sheets that day and the only ones in town that were in stock were Rosco. I bought 8 sheets of this nice purple for use on S4 pars and put them in place. It was a conference at the convention center and the pars were used to uplight fabric columns. After about 2 hours, I got called from the interior decorator that had been hired to design the fabric, flowers, and decorative lighting. She said that the lights weren't purple anymore. I inspected the gels, and they had completely washed out. There was a hint of purple at the edges, but no color at all in the middle. It was not burned or melted, just no color.

Our theory is that this was old gel. The one shop in town that stocks gel has at least 20 of every color that Rosco makes, so it is possible it has been sitting there for years. Is this possible?

#### icewolf08

##### CBMod
CB Mods
There are many reasons you could have lost your color. If you were using the S4 PAR EA fixtures, and they were being used as up-light, all the heat from the lamp and the IR and UV radiation were passing through the gel. You would have nearly 100% of the gel damaging heat and radiation hitting the gel. The S4 PAR MCM would have removed some of the radiation from the light and may have saved you some gel, but since heat rises, you would still be directing the rest through the gel. Also, if you picked a "nice" purple, it was probably very saturate, with a low transmission rate, so the chances of it burning through are greatly increased, especially because you probably ran the lights at very near to full intensity.

I doubt it was a case of old gel. If your local supplier really keeps 20+ sheets of each color in stock all the time, there is probably a high demand for color, and they probably sell it. Also, I have a huge color inventory at my theatre, much of it has been sitting around for years and years, and it doesn't seem to matter if color is new or old, if the color is going to burn through, it happens to the new and the old alike. In my experience anyway.

#### derekleffew

##### Resident Curmudgeon
Senior Team
I second what Icewolf08 said. In your application, only Apollo Heat Shield (or maybe another brand) and Color Extenders would have helped your situation. Even then, using a color such as R59 in S4-PAR EA uplights running at 100% is dicey at best.

Counter-intuitively, I've found color media fades/burns faster in WFL/MFL than in NSP/VNSP. Who can explain that?

#### JD

##### Well-Known Member
It was a conference at the convention center and the pars were used to uplight fabric columns. After about 2 hours, I got called from the interior decorator that had been hired to design the fabric, flowers, and decorative lighting. She said that the lights weren't purple anymore.
I noticed at Disney that they were using diachronic plates in most of the stationary indoor S4's. Guess they got tired of changing gels! Sounds interesting, but I am sure expensive to use in 6 inch frames, and many of their 64's (8 inch frame) were that way as well. I would suspect for the rest of us that they would be too fragile. Anybody else using them on here?

One funny effect, when you are off axis, the gel is of course a totally different color! Always a bit of a brain tease to see a light that looks to be gelled yellow throwing a deep violet beam! Kind of a neat effect...

#### icewolf08

##### CBMod
CB Mods
I have used dichroics on occasion. Sometimes I designer needs the purity of color that you get from them, and sometimes they like them for the funky colors that you can get with them. I also use the 2" rounds in the MR-16 track lighting above my desk in the booth because I was tired of replacing gel. It is true though, people walk in the booth and wonder where the blue light is coming from since the off angle of the dichroic looks pink-ish.

#### derekleffew

##### Resident Curmudgeon
Senior Team
I noticed at Disney that they were using diachronic plates ...
JD, the word is "dichroic."

...Guess they got tired of changing gels! Sounds interesting, but I am sure expensive to use in 6 inch frames, and many of their 64's (8 inch frame) were that way as well...
Certainly a greater upfront cost, but once one figures materials and labor costs to replace color media over the five year or more lifespan of the attraction, glass and/or dichroic filters become cost effective. As for their fragility, dichroic filters are no more breakable than an S4-PAR lens, but it's less disheartening to see a $6 lens broken than a$100 filter.

...One funny effect, when you are off axis, the gel is of course a totally different color! Always a bit of a brain tease to see a light that looks to be gelled yellow throwing a deep violet beam! Kind of a neat effect...
Most architectural installations using dichroic filters always specify either a top hat or egg-crate/hex louvers to prevent the audience from seeing this adverse effect. Depending on the fixture type, it can be observed in the beam as well.

#### JD

##### Well-Known Member
Counter-intuitively, I've found color media fades/burns faster in WFL/MFL than in NSP/VNSP. Who can explain that?
As odd as it seams, the VNSP (and even ACL's) actually produce the most even output across the surface of the lamp. This is due to the fact that the lamp is working more like a beam projector, using mainly the reflector to direct light. (Of course beam projectors have the lamp front blocked and pars don't.) The wider floods use a lens much like a headlight. The high refraction ridges disperse the light, but also serve like magnifying lenses (at close range) and produce hot spots on the gel. Although there are some exceptions, I must admit that I observed the same lifespan issues when using the large par based shows popular back in the 80's.

Last edited:

#### gafftapegreenia

##### CBMod
CB Mods
Apollo and Lee gel are double coated polyester for color consistancy, while Rosco and GAM are dyed polyester. The Lee HT consists of polycarbonate material, which has a higher resistance to warping and color migration.
(Edit- Wow Footer, you know when I sit down and open the 'Booth, now don't you?!)
I thought most Rosco colors used their "extrusion" process that they advertise so much.

#### derekleffew

##### Resident Curmudgeon
Senior Team
Thanks, JD. That's the best explanation of the phenomenon I've ever heard.

Senior Team

CB Mods
Ah, got it now.

#### kwotipka

##### Active Member
I think the issues you are having are a combo of light and heat. If possible, be sure that you have ample space for the heat to escape especially if the fixture is point directly upwards. I see these types of issues with bigger fixtures (2K tung and HMI). You have got to have space for the heat to go. Also, if you are working with short arc / HMI / HID light sources, look into some UV blocking gel but again make sure that you put some space between the gels.
At one point, I had a local sheet metal shop make up some gel frames for some PAR64's we were using as uplights that held the frame at about a 30 degree angle when it was in the light. This allowed some of the heat to escape and the gel still covered the beam. The colors still faded from the intense beam passing through them but they didn't do so as fast nor did they "krinkle" up.
kw

Senior Team
Fight Leukemia

#### stantonsound

##### Active Member
There are many reasons you could have lost your color. If you were using the S4 PAR EA fixtures, and they were being used as up-light, all the heat from the lamp and the IR and UV radiation were passing through the gel. You would have nearly 100% of the gel damaging heat and radiation hitting the gel. The S4 PAR MCM would have removed some of the radiation from the light and may have saved you some gel, but since heat rises, you would still be directing the rest through the gel. Also, if you picked a "nice" purple, it was probably very saturate, with a low transmission rate, so the chances of it burning through are greatly increased, especially because you probably ran the lights at very near to full intensity.
I doubt it was a case of old gel. If your local supplier really keeps 20+ sheets of each color in stock all the time, there is probably a high demand for color, and they probably sell it. Also, I have a huge color inventory at my theatre, much of it has been sitting around for years and years, and it doesn't seem to matter if color is new or old, if the color is going to burn through, it happens to the new and the old alike. In my experience anyway.

The problem with this theory is that we do this often (at least twice or three times a month) and we have never seen this happen before. Also, the local vendor that stocks all of the gel is a chain and they are required to. They also stock every gobo as well.....but most all of the theatres in town buy from another vendor.