[BarryE]

I'm not sure they are actually gel. I've got a set and they seem to be simply plastic. This article says it isn't likely any are gelatin that are made today:
How to use flash gels to color your lighting | Discover Digital Photography

... and to BigDave I think the film is uniform, plastic.

---------- Post added 12-31-19 at 04:45 PM ----------

It could be a generic term being used for historical reference's sake, but easy enough to test. If it is acetate allthe way, then they got quite hot in the box! Just wondering, was there an incandescent modeling light in the box with the flash?

Not modelling lamp ... but as I read on there's a possible answer that gives some extra info to come ...

---------- Post added 12-31-19 at 04:52 PM ----------

I looked online and found multiple other brand failures. Most involved full power some 1/2 power in rapid succession. Almost every mention said dark red was the worst for heat related failure likely due to the absorbed spectrum.

That may well have nailed it. I also found many moans about different brands. What I hadn't spotted was that dark red was worse.

I was lighting red wine bottles with a subtle indicative stripe of red down one side. The key lights on the bottle were two narrow soft boxes. I tried to get light into the bottle from behind, but I ran out of joules. So I used the gel. I know I was at low power as it was just an indication of red. Where the recycling may have been a little quicker than I appreciated was during set-up, as when I was swapping out bottles there was plenty of time for the flash units to cool. Must be careful in future.

Many thanks ...

---------- Post added 12-31-19 at 05:03 PM ----------

From Rogue: As background I was using a 3 1/2 stop red gel, but I was zoomed out. I now need to be a little careful ...

I did pass along your message to my boss to get his feedback too.

We have tested these gels and we have noted that there can be deformity (crinkling, smoking) on the darkest gels, those with f/stop loss values of 3+ stops, when the flash is fired at full power. We tested the gel attached with a gap, with the flash at a zoom of 28-50mm, though we did not conduct this test with the flash inside a soft box. However, we never had a gel melt and adhere to the flash head.

It is possible a longer zoom setting on the flash head (105-200mm) would focus the light energy of the flash into a smaller area, and then when combined with a darker colored gel stretched tight over the flash head could melt the gel’s polyester film.

The lighter colored gels do not absorb as much light energy, and therefore should be spared from heat deformity because they will not get as hot.

Just thought I’d share these additional thoughts with you in case you find it useful.

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Last edited by BarryE; 12-31-2019 at 10:06 AM.

[kaseki]

In addition to a deep red dye absorbing most of the energy in the visible spectrum (color temperature weighted), what usually isn't considered is that xenon lamps have strong lines in the near IR. Line heights and widths can vary with lamp pressure and additives, along with current density. Depending on what a given dye does at that wavelength, the added lamp output there could modestly add to the visible spectrum absorption differently for the red dye than for some other colors. (Example plot is from Wikipedia.)

[BarryE]

In addition to a deep red dye absorbing most of the energy in the visible spectrum (color temperature weighted), what usually isn't considered is that xenon lamps have strong lines in the near IR. Line heights and widths can vary with lamp pressure and additives, along with current density. Depending on what a given dye does at that wavelength, the added lamp output there could modestly add to the visible spectrum absorption differently for the red dye than for some other colors. (Example plot is from Wikipedia.)

Further clarity. Thanks ...

---------- Post added 12-31-19 at 06:12 PM ----------

In addition to a deep red dye absorbing most of the energy in the visible spectrum (color temperature weighted), what usually isn't considered is that xenon lamps have strong lines in the near IR. Line heights and widths can vary with lamp pressure and additives, along with current density. Depending on what a given dye does at that wavelength, the added lamp output there could modestly add to the visible spectrum absorption differently for the red dye than for some other colors. (Example plot is from Wikipedia.)

Further clarity. Thanks ...

---------- Post added 12-31-19 at 06:17 PM ----------

Just had a thought. Rather than Rogue gels I looked up stage gels designed for hot lights. There are many suppliers. For my flash of red, this is probably a better option. Then I can use the Rogue gels for the less optically dense filters, eg the 1 and 1/2 stop colour correction.

I've asked Rogue for recommendations for removing the last traces of their, now pink, film I have on my flash head. Interested to see what they say ...

Wonder how many folk have lost interest in this ;-) ?

[swanlefitte]

If a red gel eats 3.5 stops full power would be like 1/12 power wirhout. That means to get 128th power the flash is already at 1/24. I wouldn't be surprised if the flash was higher power than realized.

[BigDave]

Just had a thought. Rather than Rogue gels I looked up stage gels designed for hot lights. There are many suppliers. For my flash of red, this is probably a better option.

\

That's a great alternative, and probably you can got a great deal of filter for a reasonable price. However keep in mind that the light source in stage lights is well behind the filters in stage lights, and the glass lenses are designed to take heat, even absorb it. Though they are on for far longer than a flash would be, so they will probably fair better. Just presenting any pitfalls so money is not wasted. Let us know how it works out if you go this route...and in regards to interest level, no, this thread is both interesting and useful.

[BarryE]

Rogue have informed me they have passed on my enquires/problem to Lee (the material manufacturers). So they're interested.

I'll feed back if/when I hear more, though I've been informed it will be after the 6th Jan.

This site in the UK Lighting Gels / Lighting Filter Colours | Stage Depot sells a 61x50 cm, high temp sheet of gel for around £10 plus p&p. This will be way forward. My current plan is to use a diffuser cap, or similar, and replace the diffuser part with the red gel, maybe with ventilation holes, making a simple to use cap when required. Could use different strengths. Or I might just keep it simple and tape over a large bubble's worth of gel, with ventilation holes - at the price, it's going to be cheap to experiment.

I've managed to remove 99% of the red tint from my flash head with a citrus glue remover. I can just detect a trace remaining when the light catches the complex lens pattern etched in the flash head.

Almost got to the end of this little saga. I'll report back when I hear from Lee.

Happy New Year to you all ...

[automorphism]

Actually, I just used Rogue gels today. And I remember that in the instruction manual it says to attach the gels and allow space between the flash head and the gels. It specifically says don't place the gels touching the flash head. Perhaps this is why?

[kaseki]

Actually, I just used Rogue gels today. And I remember that in the instruction manual it says to attach the gels and allow space between the flash head and the gels. It specifically says don't place the gels touching the flash head. Perhaps this is why?

One might consider that the flash head optics are themselves capable of getting hot, if not due to light absorption then to conduction and convection from the ultimately much hotter flash tube fused quartz envelope and electrodes.