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Thread: Why do my Beseler enlargers have a spacer between heat absorbing glass and condenser?

  1. #1

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    Why do my Beseler enlargers have a spacer between heat absorbing glass and condenser?

    I've been exposed to Newton's rings before with an old Paterson enlarger, but my question does not involve a near negative-to-glass contact. On my Beseler CB-7 and 45 MXII, the heat-absorbing glass is separated from the upper condenser by a spacer ring -- probably 1/16-1/8" thick. I'm wondering why the spacer is there. I don't see how it would produce Newton's rings if removed. I could run some tests myself, but I thought someone here would have an explanation for the spacers. It is probably just to avoid scratches. Any thoughts?

  2. #2

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    Re: Newton's rings

    I'm not familiar with the construction of your enlargers, but I'd speculate that the spacer is not involved with an NR issue, but rather to isolate the warm/hot heat absorbing glass from contact with condenser which may cause optical distortion in the non-uniformly heated condenser. Your description implies that if the spacer is removed, then the h/a glass could come in contact with the condenser. Are you certain your condenser is glass and not (OMG!) plastic?

  3. #3

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    Re: Newton's rings

    Thanks for the response. I am sure the condensers are glass. I had not thought about the heat issue with the condensers. I had always thought about the heat-absorbing glass as trying to protect the negatives! They are obviously there for a reason, but can they remove that much heat with a long exposure to make a difference? How much heat -- created by a 100 watt bulb would result in a condenser distortion if the heat-absorbing glass was not there?

    Is it there to protect the condenser or the negative/slide? Or both! Curious minds want to know!

  4. #4
    Drew Wiley
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    Re: Newton's rings

    If your neg can be warped by as much as a sixteenth or even eighth of an inch, parts of it are going to out of focus too!

  5. #5

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    Re: Why do my Beseler enlargers have a spacer between heat absorbing glass and conden

    Don't know the specifics of the construction but the spacers could be there to create an air space to enhance the heat absorbing effect - the hot air can escape and brings a cooling effect.
    Yet another reason that comes to mind is that the condenser is probably not a heat hardened glass and should not be in a direct contact with a heat source - which the heat absorbing glass paradoxically is.

  6. #6

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    Re: Why do my Beseler enlargers have a spacer between heat absorbing glass and conden

    I don't how how the heat could escape, because it's pretty tight.

    At this point, the question is:

    Is heat absorbing glass used to reduce heat on the negative, the condenser, or both?

  7. #7

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    Re: Why do my Beseler enlargers have a spacer between heat absorbing glass and conden

    Quote Originally Posted by xkaes View Post

    Is heat absorbing glass used to reduce heat on the negative, the condenser, or both?
    Well, because the condenser is between the film and the heat absorbing glass then logically you have to reduce the heat on the condenser if you want to reduce it on the film.

  8. #8

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    Re: Why do my Beseler enlargers have a spacer between heat absorbing glass and conden

    Why not reduce the heat AFTER the light goes through the condenser if the purpose is to reduce the heat to the negative?

  9. #9

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    Re: Why do my Beseler enlargers have a spacer between heat absorbing glass and conden

    Quote Originally Posted by xkaes View Post
    Why not reduce the heat AFTER the light goes through the condenser if the purpose is to reduce the heat to the negative?
    Because you don't want to heat the condenser so much as you can heat the HA glass. The condenser is probably not heat hardened glass.
    Also, the condenser is a big chunk of glass and you don't want to heat it with a spot heat source, it could crack. The heat absorbing filter dissipates the heat so it hits the condenser in a more uniform way.

  10. #10
    Randy Moe's Avatar
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    Re: Why do my Beseler enlargers have a spacer between heat absorbing glass and conden

    I wonder if my Beseler usage makes heat a non-issue. I don't seem to heat anything up that much. I work kinda slow on one neg and one print at a time. Once focused which takes very little time, I futz a bit with paper and then print maybe 10 until I get my print how I want it. Then I make 3 more fairly quickly. Once I like a print I always do 3 more. Just in case. I don't want to come back.

    I imagine back in the day CB7's were used fast, hard and hot. Maybe using them for printing spools of medium format? I can't clean glass, dust, insert a 4x5 neg fast enough to have heat issues.

    Is heat really a worry for a hobbyist?

    I also turn down my bulb voltage...

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