We recently received an email from a well-known lighting designer asking a pretty basic question about our Protective Filters. Here is their exact email:
“In Lightwright, we have always put down IRHS (infrared heat shield). Finally, after too many years of the shops and electricians asking “what’s that,” I see the sheets at the back of the Roscolux swatchbook. I use the IRHS to keep the R79 from burning out inside a Source 4-26°. So, what should I be specifiying R-1991 or R-1995 or R-3114?”
We figured that if this designer, who shall remain nameless, didn’t know which filter to use, many others wouldn’t either. Below, we clarify the difference between the Rosco Protective Filters and describe the best way to put them to work.
Make sure that you keep at least a 1″ air gap in between the R1991 Super Heat Shield and the color filter. If the two filters end up touching, the heat will be conducted into the gel and render the heat shield filter useless. Use a gel extender if you can. Otherwise, you can insert the protective filter into the inner gel frame slot of a Source 4 or S4 Par, with the color in the outer gel frame slot. This technique works as long as the light doesn’t have too steep of a downward hanging angle, which would enable the heat shield to sag and make contact with the color filter.
In the email we received, the designer calls out for an “IRHS (Infrared Heat Shield).” Based on that description, the filter they were looking for was probably R1995 Thermashield – an optical-grade, polyester film that features a proprietary, vacuum-deposited, reflective coating on one side. When placed in front of a lighting instrument, that coating will reflect back the infrared energy from the fixture, effectively reducing the radiant heat, while transmitting 80% of the visible light. The radiant heat present in non-visible light energy can accelerate the breakdown of color molecules inside a gel filter. By using Thermashield to reflect those wavelengths back, you can extend the life of your gels.
NOTE: Thermashield was discontinued in 2022. While the plastic IR filter is no longer available, Permacolor #8100 is a dichroic glass option that filters out Infrared energy in a similar fashion (see below).
Another great way to protect your gels from infrared energy is to use our Hot Mirror dichroic glass filter. You can order an 86mm cut of the glass and install it in Source 4s using either a glass gobo holder or by inserting it into one of the gobo slots of the Universal Iris Slot Holder. Larger cuts and Permacolor Frames are also available to install the filter into standard theatrical fixtures.
When it comes to protecting gels from the heat of a Source 4, R3114 isn’t going to be much help. It will, to some degree, serve as a heat barrier similar to the Super Heat Shield (just with a lower max. temperature). Ultraviolet energy most definitely will break down the color molecules inside a gel filter, but tungsten fixtures like the Source 4 hardly generate any UV energy in the first place – so there isn’t very much ultraviolet for this UV Filter to filter out.
R3114 is useful, however, on fixtures you may use that are high in UV energy, such as HMIs or fluorescent lights. In fact, the amount of UV concentrated on the bulb of T5 and T8 fluorescent tubes is so high that we make R3114 a standard component of our RoscoSleeves for those particular bulbs.
Hopefully, that helps explain the differences between our protective filters. If you have any further questions, contact Rosco Tech Support and they can help you find the answers you need.
