This is topic Dangers of Thorium in Carbon Arc gear? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Henry Titchen (Member # 3141) on 05-04-2005, 03:25 AM:
 
Has anyone any knowledge on the dangers of Thorium in carbon arc rods? Is it possible to buy arc rods free of Thorium?

Thanks From,
Henry.
 

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Posted by John Pytlak (Member # 331) on 05-04-2005, 08:04 AM:
 
The National Projector Carbon Bulletins called them "rare-earth compounds that provide the special qualities of the light". Do you know for certain they included thorium salts?

I certainly would wear protective gear when cleaning the ash, to avoid ingesting or breathing in any particulates. Treat it the same as you would asbestos particles. And don't heat open containers of food in the lamphouse.

Thorium salts:

http://physchem.ox.ac.uk/MSDS/TH/thorium_nitrate.html

quote:

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Toxic in contact with skin and if swallowed or inhaled as dust. This material should be treated as a potential mutagen and carcinogen....Safety glasses, protective gloves and good ventilation. In the U.K. users must give at least 28 days notice to the Health and Safety Executive before working for the first time with more than 0.6g.

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Posted by Frank Angel (Member # 248) on 05-04-2005, 08:30 AM:
 
Does this thorium decompose in the arc plazma? You would think anything subjected to that kind of heat would be turned into a lump of inert stuff. Geez, and to think I used to heat my food all the time....and light my ciggies on the rods just after I extinguished the arc (wisely I stopped smoking when I was still in my 20s). But I never took any particular precautions when vacuuming the stack or the lamphouse itself of soot/ash. I guess I should consider myself lucky.

Mutagen, huh?! Hmmmm, maybe that is what's cause that third eye to grow in the middle of my forehead.
 

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Posted by John Pytlak (Member # 331) on 05-04-2005, 08:40 AM:
 

quote: Frank Angel

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Does this thorium decompose in the arc plazma?

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If elemental Thorium is the issue, it would remain in the ash.

It's been over 35 years since I regularly (mis)handled carbon ash, and still no adverse health effects. I also (mis)handled asbestos furnace cement and "Transite", heated molten lead to make fishing sinkers, used carbon tetrachloride to clean bicycle parts, and played with mercury in those environmentally unenlightened days.
 

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Posted by Martin Brooks (Member # 1269) on 05-04-2005, 12:47 PM:
 

quote: Frank Angel

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Mutagen, huh?! Hmmmm, maybe that is what's cause that third eye to grow in the middle of my forehead.

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Yeah, Frank....you really ought to do something about that eye. How do you watch 3D with that thing?

 

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Posted by Stephen Furley (Member # 1277) on 05-04-2005, 01:20 PM:
 
Morgan used to make carbons for various purposes, and there were several different core types, giving different spectral properties. Low intensity, uncoated types, used in things like sun lamps and printing down frames used to have coloured paint on the end of them to identify the core type, but I've not seen this on projector carbons. I've certainly seen ones which used cerium salts in the core, but I can't remember whether they were projection ones, or for some other purpose.

I've got a box of strange carbons somewhere; they're Morgan LCT (Low Colour Temperature?) They give a light which seems to be somewhere between a tungsten lamp, and a SON (high pressure sudium). They're difficult to strike, difficult to keep the arc stable, and produce much worse fumes than the normal ones.

I saw 'The Great Dictator' at the Loew's Jersey on Sunday afternoon; I wonder if this will be the last film that I'll ever see, at a public cinema, projected by carbon arc. I think it's quite likely.

How many people here are still burning carbons, and do you have plans to convert?
 

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Posted by Monte L Fullmer (Member # 2797) on 05-04-2005, 01:52 PM:
 
Brother! .. and how many times that I've swept out many-a-lamphouses of carbon ash, got on my hands, whiffed the dust, and cleaning out exhaust housings loaded with that stuff..

..and degreased many-a-items with Carbon Tet...

Now, I'm glad I started to play with xenon bulbs over 20 yrs ago..

-Monte
 

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Posted by William Hooper (Member # 71) on 05-05-2005, 12:21 AM:
 

quote: Stephen Furley

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How many people here are still burning carbons

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quote: Scott Norwood

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I can think of a few places that still run carbon. I have been known to work at the Avon Cinema in Providence, RI from time to time. They are still running 8mm and 7mm carbons in Enarc lamphouses on a daily basis.

In the past, I have worked at the Cape Cinema (Dennis, MA.), which is open seasonally. I am told that they still run carbon (6mm and 7mm in Peerless lamps).

Other carbon houses that I can think of offhand: IOKA (Portsmouth, NH), Cinestudio (Hartford, CT.), Wellfleet DI (Wellfleet, MA.), and maybe a few others.

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quote: Scott Norwood

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There are other uses for carbon arc lighting besides film projection, too. I recently had an interesting conversation with someone who was operating a WWII-vintage searchlight, which burned very thick carbons (non copper-coated) and is one of the brightest man-made light sources available. They were originally built for detecting enemy aircraft (in the pre-RADAR days), and are now used for advertising car dealerships and movie premieres.

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quote: Scott Norwood

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Carbons are also used in older followspots and I believe that they also have some application in offset printing (exposing plates, I think). Arc lamps (Mole Brute Arcs) are sometimes used in film prodution as well.

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quote: Stephen Furley

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I think there's only one left in Britain now, and I've never been there; it's the other end of the Country.

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If you mean the Tyneside Cinema in Newcastle, then they still burn carbons. Or at least they did in screen 2 when I last saw a film there, just over a month ago.

The Tyneside might be at the other end of the country, but at least it's on this side of the Atlantic! That having been said, it's certainly less stressful getting from here to the USA than it usaually is trying to get from York to London.
 

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Posted by Robert Throop (Member # 61) on 05-05-2005, 08:58 AM:
 
The Capitol in Rome, NY still runs 11mm carbons in Core Lites pretty regularly as does the Stanley in Utica and the Landmark in Syracuse.
Bob
 

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Posted by Tim Reed (Member # 137) on 05-05-2005, 11:09 AM:
 
SSSSSNIIIFFF!! Aaaahh! I love the smell of carbon ash in the morning!

Pretty good on sandwiches, too!
 

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Posted by Kenneth Wuepper (Member # 1174) on 05-05-2005, 12:45 PM:
 
The Temple Theatre here in Saginaw Michigan still runs 35/70 with Ashcraft lamps and 13.6mm Positives and 7/16in. Negatives at 160 Amperes. We will continue to use Carbon as long as the rods remain available and with any quality. Our last batch of Nationals came from a closed Cinerama Theatre.
 

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Posted by Henry Titchen (Member # 3141) on 05-05-2005, 04:12 PM:
 
I have carried out some more "Google" research into potential carbon arc issues. I have absolutely NO medical background.

This web page details some interesting information on "potential" issues with rare earths...news to me!

Effects on projectionists using carbon arcs

The following web page has a very interesting report as well. To quote "a relation between the observed interstitial lung fibrosis and occupational exposure to RE is highly probable."
RE means "Rare Earths"

Further study analysing projectionists lungs

Henry
 

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Posted by Monte L Fullmer (Member # 2797) on 05-05-2005, 04:39 PM:
 
These two article are quite interesting to say. Yet, what's real interesting is that these two articles have on thing in common: Is these two examples that were posted seems like the theatre itself wasn't plumbed correctly for proper lamphouse exhaust procedures.

One would think if such a device such as a carbon arc lamphouse, with all of the heat involved, would need such an effective lamphouse to draw out any fumes and heat from the usage itself and save on from busting mirrors left and right because of too much heat on the mirror from the arc.

In all of the theatres that I've ran with carbon arc, I've never had any sort of problem with fumes as mentioned due to effective exhaust procedures taken. Just had to deal with the soot when cleaning out the lamphouses on a daily basis. And I've seen lamhouses that are horribly caked with soot and wonder how they can draw up the soot and fumes effectively.

Yet, I've seen doozies of exhaust systems, from a table fan adapted as an exhaust fan pulling the draft from both stacks that have merged together and blowing the exhaust outside through a hole in the side of the building, to stacks that just are left open up in the attic with no fan usage whatsoever-the draw is caused by air circulation that was up in the attic pulling up the soot and fumes.

...but I do miss carbon arc, for the light from the arc is so much better than any xenon out there. Xenon light just doesn't have the color spectrum as did carbon arc to make picture really look their best.

Course, now with new photographic/developing procedures, I'm sure that the color temperatures in the spectrum have been adjusted to match the light output of xenon for picture effectiveness.

-Monte
 

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Posted by James Falloon (Member # 1933) on 05-06-2005, 06:29 AM:
 
I still run carbon arc from time to time maybe 6 times a year.

Don't forget that lots of these rare earth elements (eg. thorium) are also radioactive, so just to be on the safe side, I like to treat the ash like I would with radioactive asbestos - Very carefully.

But hay, I'd be lost without my newly found superpowers
 

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Posted by John Vincent, Jr. (Member # 1791) on 05-06-2005, 08:20 AM:
 
Yes we still use carbons, planning to continue to use them until DC, and even then, would like to leave the machines in place and operational if we have the room. We use both Double Eagle and National carbons. Cape Cinema is still using them as well (one of our projectionists works in both places). He is planning on using them till DC as well, I believe he already has a digital projector in his smaller venue for independent movies.

And we're not Xenon ignorant, I have an indoor with 4 ORC's. You'd be surprised how many other theatre owners jump down my throat "switch to xenon, switch to xenon..."

John, Wellfleet DI

PS: open invitation to anyone from Film-Tech, if your on Cape Cod, please stop by!!!
 

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Posted by Jim Spohn (Member # 1547) on 05-06-2005, 09:28 AM:
 
Although we only run specialty shows, we still do , and intend to continue to, burn carbons in our lamps.
2 Super Trooper Carbon Arc Followspots
2 35mm Carbon Arc Film Projector High Intensity Lamps
1 16mm Film Carbon Arc Projector
1 Dual Lamp Carbon Arc Brentograph
We will run carbon until they are no longer availiable at any price. The use of those machines is part of the show, just like using the pipe organ .... Jim Spohn
 

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Posted by Frank Angel (Member # 248) on 05-08-2005, 04:36 AM:
 
We only run event type shows...CinEvents to be exact, but we still run XLs with Peerless Lamps burning 80A (8mm & 9mm). And it will stay carbon arc only because there's no reason to convert, even discounting the cost of new lamphouses. The only real advantage xenon gives you is the ability to automate (and fire the projectionist and replace him with a concessions/ticket-taker/porter "projection attendent." That is not any improvement the audience sees on the screen...excepts when the kid screws up. So we will stay with carbons indefinately. Luckly for me, when I built the booth in 1969, I ordered a couple of hunderd boxes of carbons based on my experience with carbon use in the commercial theatre I worked for prior. Little did I realize how much less I would use in a specialty venue. My miscalculation was like minting my own money. The money we saved buying carbon rods over the years is impressive -- it is like pork futures, only it never goes down. Too bad I didnt buy even more. No, I see no reason whatsoever to convert to xenon.

Also, carbon arc has this big, fat plazma arc ball that is just so much bigger than xenon's wimpy little peanut arc. That fat arc makes getting an even light across the entire screen and with no hot spots a piece of cake. Getting xenon to light a screen corner-to-corner uniformity without hotspots always an unpleasant challenge.

Right up until last month we were running a Strong carbon arc lamphouse behind our Eastman 25B theatrical 16mm projector. We had to replace it with xenon only because we've now outfitted that machine with long-play reels that can hold an entire feature, so we needed xenon for its longevity, not necessarily because the light looks any better (which it decidedly does not).

And just within the last year we also replaced our Strong Super Trouper carbon arcs follow spots (the name Super Trouper immortalized by the ABBA song of the same name), not because they were lacking in any way, but only because the newer crop of stage hands we are getting are not trained on carbon arcs and it is not cost-effective when you call in stage hands to run a show, and he stares at the unit like he is looking at something from an alien spaceship. We'd rather not have to spend two extra hours training them before we can start rehearsals. And it is true, the carbon arc Super Troupers are a bit more temperamental than their spiffy new xenon counterparts; they require skill (considered a BAD silly old fashioned thing in today's culture) and some dexterity to keep the light bright while still not loosing your subject. Plus, with carbon arc, there is still the short coming of the finite run-time. You simply cannot run for a full show -- you have to tell the stage manager when you are about to loose your trim so action can be covered by the second spot until you replaced your carbons. We realized that it was just easier to tell the new guys to hit the ON button and aim.

I must admit, whenever a stage hand called in sick or just didn't show up, they would reluctantly ask if I could step in to cover. They were reluctant because they thought that somehow asking the Cinema Director to run follow spot was beneath me, when in fact, I was like a kid in a candy store when I sat down alongside one of those babies. I loved working the Super Troupers....but they can kiss my ass in Macy's window if they want me to run the xenon follow spots!

I have seen the light.....and it is carbon arc.
 

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