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Thread: Using modern film in mahogany half plate dark slide

  1. #1

    Using modern film in mahogany half plate dark slide

    Hello,
    I guess this has been covered before and I am grateful if someone will point me to the correct thread, because so far I have not been able to find the answers I am needing.
    I have a lovely english half plate mahogany camera, and I normally use it with a 5x4 reducing back. It's a great back which fits the camera without any alterations to the original spec whatsoever. However my reducing back is made with a very heavy cast iron darkslide holder so I want to go back to use the original GG and the half plate mahogany slides. I have two. Book form.
    I understand that these were made for glass negs so I need to use a cut-to-size perspex/glass piece onto which i must attach the film. So as to replicate the thickness of the glass negs I presume.
    My questions are:
    how thick should this piece of perspex/glass be? I have been told 0.5 mm... is that right?
    and how to attach the film to it? What is this "jam" method I read about?
    Some american threads mention "film sheaths" (there are several for sale on ebay usa but none in uk) are these a possible solution?
    Any advice much appreciated.
    PS
    I also want to do daguerreotypes with these darkslides. I think a half plate size daguerreotype should be a wonderful thing to hold...

  2. #2
    Nodda Duma's Avatar
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    Re: Using modern film in mahogany half plate dark slide

    Use whatever thickness glass is needed to build up to a 0.050 thick glass/film stack. When I started making dry plates, pretty much all the plates from that era were that thickness so I went with that. (0.050 = 1.27mm)
    Newly made large format dry plates available! Look:
    https://www.pictoriographica.com

  3. #3
    Jim Jones's Avatar
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    Re: Using modern film in mahogany half plate dark slide

    Perhaps film sheaths could be improvised from thin aluminum sheets. One source of fairly inexpensive aluminum sheets is sold for flashing at hardware stores.

  4. #4

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    Re: Using modern film in mahogany half plate dark slide

    "I understand that these were made for glass negs so I need to use a cut-to-size perspex/glass piece onto which i must attach the film."
    - This is where jam gets sandwiched. It enables the adherence of the film sheet to a cut glass surface. You can use anything; preferably without seeds or chunks of marmalade orange rind.

    The replication of the glass plate thickness to attain the same focussing sharpness on the image plane (ground glass) is a little hit and miss. As Jason suggests - 0.050inches makes more sense; 0.5mm glass will shatter.

    In England, it's easier to source 18mm, 20mm, 22mm glass - which you can bevel around the perimeter or request at the time of cutting (approximately <0.80 per sheet for a whole plate size from any glass specialist/mirror shop). This is the foundation for bringing the thin sheet of film into the same critical measurement range as the ground glass for focussing the image. I've settled on bevelled 18mm, always bevelled. The cheaper non-bevelled alternative might require a First Aid kit in the darkroom.

    The sheath adapters exist for a number of formats. I've not seen a 5x4 inch one for years after parting with one. The sheath is built from black sprayed aluminium with 3 metal lips, approximately 3mm, which enables the sheet of film to be held in place within a book form holder. Neither have you named your lovely mahogany camera (a Gandolfi perhaps?) which had some standardisation across its cameras for these now eccentric plate holders - easier to find in the half-plate form.

    www.mrcad.co.uk in London held the last reserve of these which I could find, otherwise the only feasible non-custom solution is to acquire as many as possible online to filter out the appropriate one required.

    The Deptford Sheet metal factory crafted around 20 whole plate customised ones around 15 years ago for me. As Jim suggests - thin aluminium works and easily holds black radiator paint. The company still exist and no doubt you could achieve it DIY. The factory however will need to draft a CAD or design to allow them to follow, ideally making one draft template to check out.

    http://www.deptfordsheetmetal.com/


    Kind regards,

    RJ

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    Re: Using modern film in mahogany half plate dark slide

    RJ, Hi

    "..............I've not seen a 5x4 inch one for years after parting with one............."

    You're in luck, PM on the way

    regards

    Andrew

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    Re: Using modern film in mahogany half plate dark slide

    Manufactured film sheaths are not necessary with book type holders. You just need a stiff distance piece (plastic or metal sheet) the same size as the film - to place on top of the film. This is held in place by the central spring when the "book" is closed.

  7. #7

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    Re: Using modern film in mahogany half plate dark slide

    Book form plate holders come in different non-standardised thickness Steven.

    The difference in tolerances and the design of the book form holder, risks having the film dislodge and whipped out of the book form holder during exposure making. Even cherry jam isn't strong enough sometimes.

    This is why the metal sheath system has a particular advantage over a plain sheet of glass, plastic, or metal. The lipping traps the film in place, allowing the mahogany wood to glide over.

    Kind regards,

    RJ

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    Re: Using modern film in mahogany half plate dark slide

    Quote Originally Posted by Andrew Plume View Post
    RJ, Hi

    "..............I've not seen a 5x4 inch one for years after parting with one............."

    You're in luck, PM on the way

    regards

    Andrew

    Hi Andrew -

    This is AlmostPilot's thread - I'm sure he might appreciate the heads up!



    RJ

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    Re: Using modern film in mahogany half plate dark slide


  10. #10

    Re: Using modern film in mahogany half plate dark slide

    Thank you very much for the responses.
    My camera is called The Guilford. Made in London and Leeds.
    Still a bit confused here but I know well Alex at MrCad so i will take a stroll there with my darkslides and see what he has to say.
    I was planning to get some black pexpex and cut to size. I have used this before with success on other projects (pinhole cameras) With regards to the "Jam method" if you use it do you then pre soak the film to get rid of the jam prior to developing?

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