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Burning gel

Discussion in 'Lighting and Electrics' started by Techiegirly, Jan 1, 2008.

  1. Techiegirly

    Techiegirly Member

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    I did a search and read previous posts to pick up some tips about this situation but I have a very specific problem and I need more specific answers so here goes:

    I work in a childrens theatre that runs year round the same show sometimes 6 days a week 4 shows a day depending on the time of year. During a busy time I'm literally changing out gels in 10 of our units (6" Fresnels) that have R74 (night blue) every other day (or every 4 shows or so). 1 of the Fresnels in particular burns through VERY quickly. Sometimes I have to change him out before I change out the other 9. The theatre is very small in that most of the lights aren't more than 10 or 15' from the stage and they can all be seen from the audience. The Fresnel I struggle with constantly is such a headache because this set of Fresnels are used all alone basically at one point in the show to create night time so I can't see myself poking holes in the gels although I've been tempted to with mixed enthusiasm.

    I was thinking of using a gel extender but have done a Google search and had no luck finding any. Do they even exist for this particular fixture? If they did exist would it even work? The light is about 12-15' off the ground above the stage, wouldn't a BUNCH of light end up showing through and make this idea look pretty stupid and useless? I couldn't use a top hat because the light is so close to the stage, it would ruin the focus.

    Is it the light itself? I assume so since it burns through more quickly then the other 9 lights with R74 they are all pretty much used as often as one another in that they are a group on the board and mainly get used together. Does it need to be bench focused? Can a Fresnel even be bench focused? I feel so stupid asking that...

    What if I took the lens off? Would that make the difference? Isn't that unsafe if say the lamp were to break suddenly the lens would provide a barrier of protection certainly wouldn't it?

    I've run every idea through my little brain and I'm dying for a solution. Since this show is a permanent install I think it's important to solve this issue since we go through so many sheets of gel per week. Keep in mind we use heat sheild. We put the R74 in one frame and then the heat sheild in another frame behind it. I feel as though the heat sheild might be helping but really I can't say for sure since the only gap in between the 2 is very tiny (think 2 gels frames loaded into a Fresnel...not much space).

    Any ways...what would you do?
     
  2. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Don't remove the lens, it won't focus well and as you suggested it'll be a safety hazzard.

    You can't bench focus a Fresnel, just clean the lens and reflector.

    Not sure what size accessory slot you have on your fresnels but I think 7 1/2" is fairly standard. City Theatrical makes a wide variety of color extenders. Select Lighting Accessories and then color extenders about $27 each.

    Have you tried using a pounce wheel on your gel to let a little extra heat escape?

    You could try one of the heat shielding gel products... might help a little.

    The best bet would probably be to convince the powers that be to replace the gel with a dichroic glass filter. Might cost you $100-$200 each but in the long run you would save a lot of money on both gel and labor. I think Rosco, Gam, and Apollo can all make them for you in whatever size and tint you want. Here's the Rosco product page. Here's Apollo. It's going to be expensive but would probably pay for itself pretty quick at the rate you are burning gel.
     
    Last edited: Jan 1, 2008
  3. Techiegirly

    Techiegirly Member

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    As I said in the post we use heat sheild but it's not really working in my opinion. I was considerng a pounce wheel but am afraid light may show through. These 10 lights are used alone on one part of the show for several minutes so I fear that even tiny holes will create an issue.

    At very least if I could convince "the powers that be" to buy just 1 dichroic glass filter for the "problem" fresnel we would probably save tons of money in the long run. Thank you, I didn't even know this was an option :grin:
     
  4. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Either call your local dealer or call Rosco/Apollo directly for more info. It's one of those things that you won't find a published price on as it's going to be custom done.

    Get a price quote. Calculate how much it costs in gel and labor per week to keep going like you are... put a stop watch on yourself to see how much time it takes you to cut and change that gel. Show the boss how long it will take to break even and how much money you will save over a year.

    The best part is dichroics last forever, so 10 years from now they can still be using those same dichroics on another show with no loss of color.
     
  5. DarSax

    DarSax Active Member

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    No sweat on all the questions!

    First, you can't bench focus a fresnel, to answer your question.

    Second, I'd wager that its the focus of the fresnel. I couldn't say off the top of my head if you can put the focal point of the lens in the actual gel (or might depend on the fixture), but I'd put money on the fact that the focus is the reason the gel's burning through so quickly.

    Meaning unfortunately, I don't know a solution to your problem if the focus is necessary. I'd check that first, though. If you can alter the focus, even slightly, your problem might be assuaged greatly. (SAT word for the win!)
     
  6. Sean

    Sean Active Member

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    Try using "Gel Shield". It's essentially a plastic dichroic from Apollo. It costs ~$40 per sheet, but it is pretty expensive.

    Is this unit flooded or spotted more than the other 8 in the system? I'll bet its focus is not quite the same.

    Visit City Theatrical's website http://www.citytheatrical.com for color extenders, etc. You can get them from any real theatre supplier.

    --Sean
     
    Last edited: Jan 2, 2008
  7. Techiegirly

    Techiegirly Member

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    I'm going to check the focus on the fixture as soon as I can. I don't think the world would come to an end if I "accidently" "bumped focus" a tiny bit, especially if I never told anyone I did, they'd never notice. As I've said it's permanent installation so I feel obligated to not change a single thing especially focus. I've accidently bumped focus before and paniced until I fixed the problem as best I could.

    I checked out the color extenders and I'm afraid they'd change the focus of the light. I think I'm stuck as far as getting an extender. I believe this light is flooded so an extender wouldn't work for my given situation, correct? Especially given it's closeness to the stage???
     
  8. Sean

    Sean Active Member

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    \

    You'd have to put one in and see. They make 3" and 5" long accessories, I believe.

    If you're handy with a drill and have a couple of "extra" colorframes you could make your own, shorter extender.

    Just get some long bolts, say 1/8-1/4" diameter or smaller. Build a standoff by drilling four holes in both frames, one in each corner (but not at the edge, or else it won't fit in the light). Bolt the two frames together, keeping the frames separated a bit by using extra nuts. Then wrap the now open sides with blacktak/wrap. Not pretty, but it might help your problem.

    Also, you could use a barndoor. Some of them are designed to hold a colorframe. It's usually about 2" further from the lens, so that may help as well.

    When did the LD see this plot last? Is it possible that the fixture's spot/flood has slipped? Gravity would slowly flood the unit out, and could be the source of the problem.

    Off to bed....finally!


    --Sean
     
  9. Pie4Weebl

    Pie4Weebl Well-Known Member Fight Leukemia

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    if that light was the only one having an issue, I think it would make more sense to replace the fixture instead of spending $200 on a gel. I know lee posts the prices of the glass versions, sadly that sheet is in St. Louis and I am back in Chicagoland. Try cleaning it and check the focus. Make sure there is no black tack covering the exhaust vents on it so heat can properly escape that might do the trick.
     
  10. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    How did I come so late to this party? Techiegirly, you said you've tried heat shield in the past, with poor results. The Apollo "Gel Shield" really is superior, but any shield needs airspace between it and the color. A 3" color extender will not affect the focus of the Fresnel, even at full flood, which is most likely is as that puts the lamp closest to the lens. Another thought, do you have access to any barn doors? Most would allow you to put the "shield" in the color frame slot in addition to the barndoor, then there's a place for the R74 at the front of the barndoor. Leave all the doors wide open.

    I've never had any luck with "pouncing" gel in deep colors, to me it just gives the color media a place to start to burn quicker.

    You never told use what make, model, and lamp of the Fresnel in question. We are all assuming, I think, an Altman 6" FS, 65Q, with a 750W BTN lamp. Fixture is not rated for any higher wattage than that, so you better not have a 1000W in there!

    Another option, now that it is after 01/01/08, is Apollo's new Gel Miser!

    Lastly, you need not go to the expense of a dichroic filter. Devon Glass #148 (website colors are not accurate, call for a sample) is fairly close to R74, and glass is much less expensive than dichroic. I think Rosco also has a line of plain glass.
     
  11. icewolf08

    icewolf08 CBMod CB Mods

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    All of the heat shield and GelShield products are designed to work best with space between the color and the shield. If you put them both in the same frame it won't work, the heat needs a place to go.

    We just did a show with a bunch of dark colors, and we did the pounce wheel trick. You can't tell that we pounced the gels, but guess what... It didn't buy us much, maybe one extra performance before replacing, but that isn't that much of a savings over a long run.

    Do you have any barn doors? If you have barn doors you can offset the gel from the lens, but leave the barn doors wide open so you don't cut off the light. You will need bigger cuts of gel to get around the barn doors, but you will leave plenty of room for air and cooling.
     
  12. Logos

    Logos Well-Known Member

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    If the lantern is flooded out it's probably not the focus. To get the focal point on the gel in most small fresnels they need to be spotted right down.
    I had a lantern that just insisted on burning out gels more often than any other that I owned, I have rigged it in a situation where it is in open white in a permanent back stage. That wasn't very helpful was it. Sorry.
     
  13. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    [user]Sean[/user], what a fantastic idea! I might (am gonna) elaborate some. Use 1/4" copper tubing (does not have to be copper, but I know that is easily available), cut into (4) 1" pieces. Use 1.5" x whatever diameter round head stove bolts will fit into your tubing. The top two corners of your color frames probably already have holes drilled in them for brads/paper fasteners, but may need to drill them out depending on size of stove bolt you use. The bottom two holes should be about 1" from the edge and 1/2" up from the bottom. Now bend a frame completely open and put the stove bolts from the inside thru only one half of the frame. Turn the over so bolt heads are down. Add the copper spacers, and put the other frame on top of the 4 bolts and add (4) properly sized split lock washers and (4) nuts. Bend the first frame back into shape. Cut off/grind off any boltage sticking out past the nuts. Add your R74 to the outer frame. Don't use any BlackWrap or BlackTak unless the spill/flare is a problem. And preferably on the sides only. I should have mentioned painting the frames black with BBQ or Engine paint first. Chances are this will solve your issues, but if not, add heat shield in yet another frame closest to the lens. I'm thinking so you don't have to take the contraption apart each time to change the gel, even if next show. This would work for either 6" or 8" Fresnel. Someone more graphically inclined than I am: Want to Google SketchUp this idea?

    Techiegirly, you're now our official guinea pig for this idea. Try it and let us know the results. Colorframes are inexpensive and usually readily available, so we may solve lots of problems, with Sean's idea, for many CB-ers!
     
    Last edited: Jan 2, 2008
  14. Techiegirly

    Techiegirly Member

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    Oh my word you all have given me such great ideas!:grin:

    Unfortunately this particular theatre does not have a shop so as for rigging something up, not likely. Everything's either bought already made or...well that's it really. We do have extra barn doors hanging around however so I shall give that a try.

    We do use a heat sheild and they are in seperate frames however both are placed in the slot there in the front so really there's no room between them both at all. I feel as though we've not only been wasting our R74 but we're burning through sheets of heat sheild for abslutely no reason. I don't change the heat sheild out everytime, I only do if it's crispy, has a hole or has absorbed some of the color from the R74 in front of it.

    This is the only light that burns so hardcore that it gets a hole about every 4th or 5th show but while I'm changing out this gel the other 9 are about at their prime so I just switch those out as well since I've already got the ladder out.;)

    The focus on this Fresnel and the other 9 are "supposed to be" all the same but I'm sure it's dropped focus in the 2+ years it's been up there. I couldn't tell you the last time the LD saw this rig. I've worked there since before summer and I've yet to meet the lady.

    I think I have a lot of work to do now putting all of your ideas to use.
    Thanks!
     
  15. Kelite

    Kelite Apollo Staff Premium Member

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    <both are placed in the slot there in the front so really there's no room between them both at all.>

    That may be the weakest link in the chain here...

    Having some air flow between a shield and the gel is truly the way to go- IF you can get that kind of space on the end of the fixture.
     

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