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12 inch Goerz disassembly

 
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45PSS



Joined: 28 Sep 2001
Posts: 3198
Location: Mid Peninsula, Ca.

PostPosted: Thu Dec 13, 2001 5:02 am    Post subject: Reply with quote

I have a gorez that I would like to clean between the elements. I can remove the groups fron the shutter and mount flange and remove the thin caps on each element group but the elements themselfs won't come out of their barrels. Any suggestions that will not damage anything??
Thanks in advance,
Charles.
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SpeedGraphicBeginner



Joined: 09 Aug 2001
Posts: 13
Location: Oakland, CA

PostPosted: Fri Dec 14, 2001 11:03 pm    Post subject: Reply with quote

Hello There, Is your 12" Goerz lens a "Dagor?" If so, the elements composing the front and rear groups are cemented together. That also accounts for the fact that uncoated Dagors are good in the flare department: There are few air-to-glass splaces. Also, centering is an issue with Dagors. If elements are not properly centered, the lens suffers from focus shift. Look at Rudolph Kinglake's History of the Photographic Lens. Also, you will find interesting information if you do a web search with: Dagor AND lens on Yahoo search engine. But if my recollection is correct, the front and rear groups are cemented. Disassembly and cleaning would likely involve recentering and recementing. Is there bad fungus or lens separation?? Sometimes a less than perfect lens turns in decent performance.
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45PSS



Joined: 28 Sep 2001
Posts: 3198
Location: Mid Peninsula, Ca.

PostPosted: Sat Dec 15, 2001 4:40 am    Post subject: Reply with quote

Yes, it's a Dagor. Only slight haze and a few specs of barrel black and maybe a speck of dust or two. If there was cell seperation I would find a sutiable trash can or lens recycler. I've tried hot water bath for 30 to 40 minutes @ 120 F. and a mild adhesive remover, neither any help.

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[ This Message was edited by: 45PSS on 2001-12-14 20:41 ]
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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Sat Dec 15, 2001 3:26 pm    Post subject: Reply with quote

Since ther isn't any air space inside a front or rear element, if you can get the cells seperated from the shutter/iris/barrel then clean the inner surface, and reassemble.
Anything artefacts inside the cell will have to stay there or involve uncementing the elements

I have a couple of ancient dagors, one in a B&L iris diaphram mount and one "doppel Anastigmat with a unique aperture system (not fstops not US stops) I can remove the cells from their mount on the B&L but the Berlin Dagor is permanent. Nonethe less I've cleaned the interior on both with no problems.
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45PSS



Joined: 28 Sep 2001
Posts: 3198
Location: Mid Peninsula, Ca.

PostPosted: Sun Dec 16, 2001 5:54 am    Post subject: Reply with quote

Les, here is a better description; f6.8 Dagor, Compound flange mount shutter. Front and rear lens groups unscrew form the shutter/flange and are 1 inch long. Glass is recessed about 1/4 inch. Are you saying there is no futher disassembly without decementing the cells?
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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Sun Dec 16, 2001 3:19 pm    Post subject: Reply with quote

well I'm not, but Dr. Rudolph Kingslake, head of kodak lens research, historian, and all around deity does





[ This Message was edited by: Les on 2001-12-16 07:32 ]
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45PSS



Joined: 28 Sep 2001
Posts: 3198
Location: Mid Peninsula, Ca.

PostPosted: Mon Dec 17, 2001 4:29 am    Post subject: Reply with quote

Crystal clear as a lens should be.

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RKnoppow



Joined: 15 May 2002
Posts: 14
Location: Los Angeles

PostPosted: Wed May 15, 2002 2:15 pm    Post subject: Reply with quote

A Dagor has only four glass-air surfaces, all accessible without disassembly other than removing the cells from the shutter.
If the lenses are hazy and its not surface damage, its the cement between the elements. Each cell consists of three pieces of glass cemented together.
Lenses built before about 1947 are cemented with Canada Balsam, essentially purified pine pitch. This type of cement typically dries out and crystalizes near the periphery of the lens, leaving a yellow ring. If small this sort of edge drying does not have much effect on the performance.
Later lenses may be cemented with a synthetic cement. The synthetics do not usually have edge problems but can separate in a way that looks like large air bubbles between the elements.
Synthetic cement can also get hazy. Looked at with a magnifying glass it has a sort of orange peel look.
Canada Balsam can also get hazy from crystalization. This can look completely milky if the lens has been subjected to either very high or very low temperatures.
Lenses cemented with Canada Balsam can be separated by heating in water or on a hot plate. Synthetic cements must be boiled apart in a special solvent. It takes tempertures on the order of 350F to do this.
Its quite practical to re-cement your own lenses. The cements and solvents are available from Summers Optical. Do a google search to find their web site. The procedure is not too difficult but requires some patients. Summers has instructions on their site.
Goerz-American Dagors are mounted in cells with threaded back caps so its easy to get the glass out and the cells are reusable.
BTW, Goerz-American Apochromatic Artar lenses are also mounted the same way. These are four element air spaced types so there are two surfaces inside the cell which can get dirty. The back caps unscrew so cleaning is easy.
A great many old lenses get a coating of haze on the surfaces exposed to the air. This haze can destroy contrast but cleans off with ordinary lens cleaner. I don't know the exact cause of the haze, it seems to vary amoung makes of lenses.

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Richard Knoppow
Los Angeles, CA USA
dickburk@ix.netcom.com
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