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Thread: new 8x10 enlarger

  1. #1

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    new 8x10 enlarger

    hi everybody. I have finished to build an 8x10 b/w enlarger. I used the book by Ansel Adams as a guide. It is horizontal. I used a couple of opal plastic layers for diffusing the light of 16 normal tungsten bulbs (40w each). The problem I am experiencing is I can't successfully dissipate the heat generated by the bulbs. I tried using two fans I recovered from an old computer, but it doesn't seem to work. The opal screen is nearly 10 cm far from the negative and other 10 cm far from the bulbs. How strong should the fans be to help keep the temperature down? Can anybody suggest a solution?

  2. #2

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    Re: new 8x10 enlarger

    hello quigon,

    can you post a photograph showing the bulbs from the lens side?
    can you post a photograph showing a side view?
    I assume the arrangement is 4x4, what space is left between the bulbs? what is the diameter of the bulbs?

    some hints:
    1. there is special glass available that holds back IR
    2. you can use lamps from slide projectors having a rear mirror, just reflecting
    non-IR light
    3. you can use high power leds, although a little bit expensive
    4. there are more efficient blowers than those for pc's
    5. you can have 4 outgoing blowers, with 4 ingoing blowers at the opposite side
    6. what lens aperture do you use?


    george

  3. #3
    8x20 8x10 John Jarosz's Avatar
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    Re: new 8x10 enlarger

    When you say "normal" bulbs, do you mean normal size? If so, maybe you can try substituting fluorescent replacements.

    The IR part of the spectrum needs to be eliminated.

    The fans will get rid of the heat from convection, filtration will get rid of the heat from radiation.

    John

  4. #4

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    Re: new 8x10 enlarger

    IIRC Adam's enlarger's fan wasn't on the enlarger but was off on it's own, linked to the enlarger by flexible ducting so that vibration from the fan wouldn't be transmitted to the chassis.

    I would definately replace the plastic with at least one layer of heat absorbing glass with an airspace between it and a layer of opal glass.
    Good luck!
    "I would feel more optimistic about a bright future for man if he spent less time proving that he can outwit Nature and more time tasting her sweetness and respecting her seniority"---EB White

  5. #5
    Has Been LF Photographer
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    Re: new 8x10 enlarger

    I built an 8x10 enlarger some years ago, also inspired by Ansel's. Times had changed from when he did his however, even if it was 30 years ago when I did mine.

    Instead of incandescent bulbs, I used an Aristo 8x10 cold light head. Worked perfect. No heat.

    If I were to use incandescent bulbs, I'd outboard a squirrel cage fan and pipe the air to the chamber with a flexible tube, maybe a dryer vent hose as mentioned above by John.

    I don't know anything about your computer fans, but they sound like they would be woefully inadequate for this type heat. In addition, I assume the reflectors in the bulbs focus the heat forward right into the negative area.

    I found that with the lack of heat, I was able to use a piece of window plate glass behind the negative, have the negative against the glass, and nothing in front of the negative between it and the lens. It eliminated the dust issues so prevalent in glass equipped carriers.

    Just sold it a few months ago on this forum to a member in New York.

  6. #6

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    Re: new 8x10 enlarger

    The 8x10 (and 5x7) enlargers that have the light source directly behind the negative always used a special "heat absorbing glass" between the lamp and the negative, in addition to some diffusion material (sand blasted glass, opal glass). The heat absorbing glass needs to be nearest the lamp, and then the diffusion media towards the negative.

    You might consider the techniques used by the manufacturers when designing a dichroic color head..which is to use a bank of high intensity lights off to one side aimed into a white mixing chamber. With no lamp directly above the negative, the heat to the negative is drastically reduced, and the fan cooling is only used to keep the bulbs cool.

  7. #7

    Cool Re: new 8x10 enlarger

    I have a 10x10 Durst. Got it with the dichroic head, two each 1000watt bulbs. Came with one hell of a fan system, two 220v fans linked to the head via 2 inch flexible hoses. Noise from hell.

    Got a beseler 8x10 cold light, mount gel filters on the lens, happy and quiet.

    If you want the dichroic head, we can do a deal. extra fans also.

  8. #8

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    Red face Re: new 8x10 enlarger

    Thanks everybody!
    I can't show any pictures for now, as I own no digital camera, (I'll borrow a friend's).

    Anyway, the arrangement of the bulbs is 4x4. Each bulb is 40w. Between bulb and bulb there is a space of 3 cm.
    When I say that they are 'normal' I mean that they are general purpose use (bedside table, for example).
    Wouldn't fluorescent lights substitute be difficult to control via a combi timer? (They do not switch on immediately, they are not stable, ...).

    To start with, 1) I think I'll try this special "heat absorbing glass". 2) I'll find bigger fans.

    I would like to buy a cold light head, but I'm having problems in finding a second hand here in Italy, which is the place where I live.

    Again, thanks to all for your ideas.

  9. #9
    ic-racer's Avatar
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    Re: new 8x10 enlarger

    Quote Originally Posted by quigon View Post
    Thanks everybody!
    I can't show any pictures for now, as I own no digital camera, (I'll borrow a friend's).

    Anyway, the arrangement of the bulbs is 4x4. Each bulb is 40w. Between bulb and bulb there is a space of 3 cm.
    When I say that they are 'normal' I mean that they are general purpose use (bedside table, for example).
    Wouldn't fluorescent lights substitute be difficult to control via a combi timer? (They do not switch on immediately, they are not stable, ...).

    To start with, 1) I think I'll try this special "heat absorbing glass". 2) I'll find bigger fans.

    I would like to buy a cold light head, but I'm having problems in finding a second hand here in Italy, which is the place where I live.

    Again, thanks to all for your ideas.
    You certainly will be trading one set of problems for another if you go to fluorescent at this point. I'd try some of the other suggestions first. Also, can you measure how hot it is getting? Even a properly cooled incandescent 8x10 unit will be hot.

    As a comparison, the 250w lamp in my 4x5 Omega is cooled with a single 12cm blade computer-type cooling fan.

    I like the suggestion of a separate bowing or sucking fan connected to the head with a large flexible tube. Look at the size of the hose and size of the exit air holes on Adam's rig and copy accordingly.

  10. #10

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    Re: new 8x10 enlarger

    Quote Originally Posted by quigon View Post
    Thanks everybody!

    Anyway, the arrangement of the bulbs is 4x4. Each bulb is 40w. Between bulb and bulb there is a space of 3 cm.
    When I say that they are 'normal' I mean that they are general purpose use (bedside table, for example).
    You're trying to dissipate about 640 watts of heat from your light source (16 X 40 Watts) -- that's roughly 1/2 of a common hair dryer. A very simple thing to do is to try to determine how much light you really need and re-size your light bulbs. For example changing to 20 Watt bulbs is just one F-stop. Also, I'd try to use compact florescent bulbs -- CF Bulbs -- a 13 watt CF bulb equates to about 60 watts of light.... the down side to some of the inexpensive CF bulbs is that they need to warm up a little before you get full brightness.

    Bill Riley

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