Film-Tech Forum ARCHIVE: Cleaning Reflectors

This is topic Cleaning Reflectors in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Ian Bailey (Member # 1752) on 01-21-2004, 09:21 PM:

What is the best way to clean the mirror surface on a Xenon reflector when it appears dull?(I have Super Lume-x lamphouses)

Posted by Dave Macaulay (Member # 813) on 01-21-2004, 10:10 PM:

There are dichroic and rhodium plated SLX reflectors, it's 99.9% certain you have the dichroic ones. The surface coating is pretty easy to scratch or even remove while cleaning them. I take the mirror off and put the whole thing in a sink, hose off surface dust with warm water, then gently wash it with mild detergent and a soft sponge, using very light pressure. Final rinse with quite warm water then very gently dry with a clean pure cotton towel. Minimize the time and pressure of any contact with the surface, don't use any paper products other than kimwipes or equivalent. Kleenex is like sandpaper.
Some milkyness is a result of the surface coating aging in the hot and high UV environment in the lamphouse, this will not clean off. They can be fairly nasty looking and still work well though. Although there are places that will recoat mirrors the cost is not enough less than a new reflector to get me to try it. I haven't run into an old lamphouse with unavailable mirrors that was worth the cost of recoating. Years ago the Ontario Place Imax system had a bizzarro vertical 30kW lamphouse with a water-cooled collector made of pure unobtanium, we had it recoated a few times with OK results.

Posted by John Pytlak (Member # 331) on 01-21-2004, 10:29 PM:

Edmund Optics also offers a variety of cleaning products for coated optics:

http://www.edmundoptics.com/IOD/Browse.cfm?catid=250

http://www.edmundoptics.com/IOD/DisplayProduct.cfm?productid=1638

Posted by Ian Bailey (Member # 1752) on 01-22-2004, 05:47 AM:

Thanks Guys [thumbsup]

Posted by Paul G. Thompson (Member # 655) on 01-22-2004, 11:42 PM:

Contact Ultra-Flat. They are the reflector experts, and they will not lead you down the path to BFE.

Posted by Bill Enos (Member # 440) on 01-23-2004, 01:14 AM:

Is there a reason why dichroic coatings are not applied to the rear surface of the reflector? I had some rear coated dichroic mirrors in the old Peerless Magnarcs, it sure took the risk out of cleaning, they lasted about 20 years too. Ultraflat told me about a year ago that they could not put a dichroic coating on my Kneisley mirrors, only a hot coating. They were also a little more expensive than new mirrors. Would a small fan blowing on the backside of the reflector help it last longer?

Posted by Michael Schaffer (Member # 1204) on 01-23-2004, 02:43 AM:

I just checked a reflector which had been installed just 6 weeks or so ago after the lamphouse blower had failed and the lamp had grilled the old reflector (it is one of the rare Christie CXC consoles).
The new reflector has already started shedding the coating a little bit. I have never seen this before. Could it be that some reflectors lose the topmost layer of the coating during the first weeks?

Posted by Ian Bailey (Member # 1752) on 01-23-2004, 04:09 AM:

Michael-I had this happen to me recently when I replaced a reflector in a SUPER LUME-X.The coating started to flake off badly within 4 weeks.I contacted my supplier who contacted STRONG and I received a replacement at no cost.It looked to me to be a very thin coating that didn't adhere to the surface properly,it was flaking in very small pieces.The reason I posted this question was that my reflectors are dull to look at(not shiny like a mirror).We are very close to the ocean so it could be salt in the air(I'm not sure),all I know is the air-con units on the roof are rusting away faster than I would like to see.

Posted by Jack Ondracek (Member # 1466) on 01-23-2004, 11:36 AM:

quote:
Is there a reason why dichroic coatings are not applied to the rear surface of the reflector? I had some rear coated dichroic mirrors in the old Peerless Magnarcs, it sure took the risk out of cleaning, they lasted about 20 years too.

All of the crap that arcs shot out pretty much made front dichroics impractical. In the best of worlds, you had to clean those reflectors all the time. With a front-coat, all of the normal cleaning methods went out the door. The first time you put Bon-Ami on one of those things, there went your coating.

The first dichroic I ever had was installed on a Strong lamphouse (the one with the bi-metal switch controls over the feeds). The picture was fantastic! Cleaning the reflector just about put me into overtime. Whoever the reflector came from (I just assumed it was Strong) provided a two-solution procedure that had to be used to loosen up the deposits. I don't remember exactly what the final step was to polish the thing, but it was definitely a touchy process.

You wouldn't have to worry about any of that with a rear coat. For some odd reason, nobody seemed to be too concerned about light loss until xenons came out! [Wink]

Posted by Robert Throop (Member # 61) on 01-23-2004, 02:30 PM:

In the Ashcraft Core Lite and Super Core Lite lamps where there was a constant stream of air across the reflector front surface dichroics were used all the time. Cleaning was not a problem. Just a little Windex every day. In fact the only rear surface dichroics I remember were the very early ones from the fifties. Both Strong's Tufcold and the Balcold reflectors Ashcraft used were front surface after about 1960.

Posted by Scott Norwood (Member # 30) on 01-23-2004, 02:42 PM:

With carbon arc lamps, I was always told to use _only_ a clean, dry cloth to wipe down the reflectors before each show. Would Windex (or something else) be a better choice?

Posted by Paul Mayer (Member # 355) on 01-23-2004, 02:56 PM:

With the glass reflectors used in Strong followspots (rear surface), before first show each night (when the reflector is cool) we'd clean them with a spray-on glass cleaner and wipe dry with a clean cloth. After that, anytime the arc was shutdown (especially after the first burn-in) we'd just wipe any soot off with a dry cloth. Only used Bon-Ami if the soot had built up or baked into the glass. Also used a razor blade to knock off the occasional copper blob on the glass. Gentle striking of the carbon rods kept the pitting of those glass reflectors to a minimum.

[ 02-11-2004, 06:58 PM: Message edited by: Paul Mayer ]

Posted by Bill Enos (Member # 440) on 01-24-2004, 08:41 AM:

If I'm reading these comments correctly, any light loss from a rear coating would be soon gained back by cleanability and possibly reduced flaking. Do non dichroic coating coatings last any better?