6th Dec. 2006
Just wrapping a show that’s been up for almost a year now. We have about 18 image 80s that were hung straight down over sets like soft boxes. I had them tubed with alternating tungsten and daylight tubes so that I could control the colour temp of the ambiance in each set. Most had 250 or 216 on the gel frames and some, depending on the set had egg crates in them as well.
As the crew was striking it was discovered that almost all of the tubes had a brown mouldy looking substance on the inside of the plastic jacket. Like caramelised dust, adhesive, I don't know. Its hard to tell. Additionally the rubber gaskets that secure the plastic jacket to the tube on either end of the fixture are loose and also brown.
We were shooting on a dusty soundstage and the tubes were never replaced. I need some resolution to this as I have to ultimately explain why our producers have to buy over a hundred expensive kino tubes.
Any help or past experience is much appreciated as always!
It sounds as if over the period you explained, heat build up and dust caused the seals to melt. if it is on the inside, then there could be little else.
Erik Messerschmidt wrote:
>>We were shooting on a dusty soundstage and the tubes were never >>replaced. I need some resolution to this as I have to ultimately explain >>why our producers have to buy over a hundred expensive Kino tubes.
The cumulative heat build up exceeded the temperature at which the fixtures were designed to operate. Heat rises and collects at the ceiling adding to the cumulative heating effect.
Recently in my neighbourhood an ice skating rink nearly burned down.
What's to burn in an empty ice rink, you ask?
Everything but the ice. Due to the cumulative heat generated by mercury arc lamps, these lights set the "fireproof" insulation on fire; the burning insulation in turn dripped onto the plastic seats below setting them on fire until whole bleacher sections were involved.
From my NFPA film experience, I learned that anything will burn if it gets hot enough.
IA 6090 DP
It sounds like the lamps do not need replacing, only the safety sleeves. The glue that seals the end caps and safety sleeves can crystallize from heat over time when the lamps are not ventilated, as you described.
The Kino Flo rental department here in Burbank as a matter of maintenance replaces the safety sleeves on its lamps every year to two years. Your production company can check with the regional Kino Flo dealer or distributor for availability of the safety coating replacement kits.
Kino Flo, inc.
>>The glue that seals the end caps and safety sleeves can crystallize >>from heat over time when the lamps are not ventilated, as you >>described.
Thanks so much for the help Scott, it certainly explains the problem. Maybe Kino should consider switching adhesives or at least publishing a warning about using the fixtures in this orientation.
Next time I'm tempted to rig like this I'll think twice!
>>We have about 18 image 80s that were hung straight down over sets >>like soft boxes.... Most had 250 or 216 on the gel frames and some, >>depending on the set had egg crates in .them as well...
In my experience, Kino tubes can get very hot without proper ventilation. I've even seen 'em melt an eggcrate that had too many layers of gel clipped on- and that was in an upright position. I learned to avoid clipping multiple gels to eggcrates early on, even though it is more of a hassle. The tubes need some breathing room. I can imagine that if you had them hanging down with gels attached to the eggcrates for such a long period if time, heat build-up is likely the culprit.
Thanks for the "heads-up". If I require a similar setup in the future I think I will consider just building frames out of 1 x 3's and screwing in the reflectors and the harnesses to help dissipate heat.
But I wonder if that would even be enough...
DP, based in Lithuania
If these tubes were getting so hot, I wonder how their colour temp and CRI fared. I have always understood that ventilation was very important for Flo bulbs (don't end cap and gel the doors, not the eggcrates), and that even after a relatively short time colour temp would increase and CRI would decrease.
If they get hot enough to melt that glue, were they hot enough to go significantly off-colour?
In fairness to KinoFlo, there are very few adhesives that won't begin to break down under a year's worth of continuous cycles over-heating and cooling.
IA 600 DP
Further to you question regarding Image 80 rigging :
When rigging larger fixtures such as the Flathead 80, Image series or Wall-O-Lites in a studio for a prolonged time period we recommend using uncoated lamps. First: this allows the lamps to operate coolly and stay more colour stable. Second: the non-coated lamps cost less and you don't have to replace old safety sleeves. Safety coating is very popular because it helps protect lamps from breakage when used in our portable lighting systems (such as the 4Bank, Double and Single fixtures) during location shooting, and from rough handling in general. Also, if a lamp does break, the safety sleeve shields the cast and crew from the pieces of glass.
Mitch's related question regarding the mired shift and colour rendering of True Match lamps in these fixtures is a good one. Heat is the enemy of good colour in fluorescents, so anything that increases ventilation will improve the operating performance of the lamps. When orienting an Image 80 fixture facing down, it can produce heat at the cathodes well over 160 degrees F (70 degrees C), and result in a 5cc (or 8M) increase in the green spike. The Kelvin shift could be as much as 550 degrees Kelvin. To reduce the heat build up, rig the fixtures angling up 2% to 5% at least. This allows some of the heat to escape up and out the vent array. Lamp choice will also affect lamp performance. The True Match 900 series 3200K and 900 series 5500K lamps were formulated for use in long-term, low-ventilation rigs. The 900 series lamps stay a bit closer to their rated Kelvin and colour rendering than the standard 800 series 3200K and 5500K lamps when operating at extreme temperatures. Note: the one 800 series lamp that does very well in hot environments is the True Match KF29 (2900K) lamp. It was formulated for long-term studio installations and more closely matches the real-world Kelvin temperature of studio incandescent hot lights than 3200K fluorescents.
Scott C. Stueckle
>> Further to you question regarding Image 80 rigging :
>>When rigging larger fixtures such as the Flathead 80, --- etc.
Thanks Scott -
I had the 800 series KF29s and the 900 series KF55s in the heads.
We did of course have a little green spike in the overheads, but not enough to make me regret the choice to use them. Often times we were only running three or four tubes in each unit, and were usually mixing many different colour temps anyway so it didn't concern me too much. In fact, the magenta in the tubes before they warmed up was often more of a problem then the later green shift. Whenever I'm working with fluorescents I just accept the fact that I'll be fighting colour temp the entire time.
I'll consider lamping the heads without the safety sleeves next time I do this, although that also makes me concerned. I can just imagine a wild boom pole swinging and taking out all 8 tubes over the cast.
In actually the Image 80s allowed us to quickly switch the mood in sets, it was a very handy tool and I'll continue to use them, just with a little more discretion.
Thanks for everyone's thoughts!
Erik "long live incandescence" Messerschmidt