Solved: Enlarger mixing box was causing mark on prints

Discussion in 'Darkroom Equipment' started by adelorenzo, Jan 20, 2018.

  1. adelorenzo

    adelorenzo Subscriber

    Messages:
    1,098
    Joined:
    Mar 10, 2012
    Location:
    Whitehorse, Yukon
    Shooter:
    4x5 Format
    I managed to solve an issue with my LPL 4550XL today. I figured I would post here in case someone has the same problem in the future.

    I was getting an inch long mark on some of my prints as shown in the photo. It was only happening with 4x5 enlargements so at first I thought it might be something with my 135mm lens but I couldn't see anything.

    I decided to pull apart the head and there was a black mark on the white plastic on the bottom of the mixing box. Maybe a scuff mark of some kind. It was near the edge so not affecting smaller negatives. I buffed it for 30s with a cloth and it went away. Just finished some prints and all is good.

    IMG_20180119_171136-01.jpeg
     
  2. Ozxplorer

    Ozxplorer Subscriber

    Messages:
    146
    Joined:
    Aug 29, 2004
    Location:
    Gold Coast, Australia
    Shooter:
    Multi Format
    Thank you for that... from my point of view checking the mixing box as a possible cause for marks on prints it not something I would have done - not even thought about either!
     
  3. Mick Fagan

    Mick Fagan Subscriber

    Messages:
    3,408
    Joined:
    Sep 13, 2005
    Location:
    Melbourne Au
    Shooter:
    Multi Format
    I agree with Fred, thank you. I don't think I would have ever thought a mixing box with a black line somewhere would have caused that.

    Always learning.

    Mick.
     
  4. Marco Buonocore

    Marco Buonocore Member

    Messages:
    419
    Joined:
    Mar 18, 2005
    Location:
    Toronto
    Shooter:
    Medium Format
    I'm glad you solved the issue!

    One of my first enlargers, a Durst M605 with a colour head, was bought used on craigslist. I was just learning to print, and wasn't perhaps as critical of my prints as I am these days. I eventually starting noticing these dark circular marks right in the middle of my prints. Lots of frustrating time later, I traced it back to the opaque white plastic at the bottom of the mixing box - it was a burn mark from a halogen bulb! Someone who had used it in the past had seemingly set the hot bulb temporarily on the mixing box, and it melted the plastic.

    I guess I could have replaced the opaque plastic, but - being Durst - it wasn't a simple piece. With the vast majority of darkroom equipment being used these days, I suspect these sorts of problems will be more common, and this sort of problem solving and jerry rigging is almost par for the course now.
     
  5. gorbas

    gorbas Subscriber

    Messages:
    575
    Joined:
    Dec 9, 2007
    Location:
    Vancouver, Canada
    Shooter:
    35mm Pan
    Hi Marco, was that plastic diffuser shaped like plan concave lens with flat part towards negative? Thicker at the centre and thinner at the edges. Maybe in future part of photography craft will be designing and running 3D printers too
     
  6. OP
    OP
    adelorenzo

    adelorenzo Subscriber

    Messages:
    1,098
    Joined:
    Mar 10, 2012
    Location:
    Whitehorse, Yukon
    Shooter:
    4x5 Format
    I have to somewhat sheepishly confess that this had been an issue for a while now that I had been kind of ignoring. Given it's location it only affected certain prints: basically 4x5, not much cropping, where there was a significant amount of featureless tone like a dark sky for example. Once I did seriously take a look for the problem it only took me 5 minutes to solve. :redface:
     
  7. Bob Carnie

    Bob Carnie Subscriber

    Messages:
    6,845
    Joined:
    Apr 18, 2004
    Location:
    Toronto-Onta
    Shooter:
    Med. Format RF
    Sometimes the foam inside would heat up and release and fall inward causing real problems, but don't feel bad we all have been there before.

    the column that the head runs up and down can sometime wear to raw which sometimes will reflect reflective light and cause nightmares to figure out where the plus density mark on the print is coming from.
     
  8. Kilgallb

    Kilgallb Subscriber

    Messages:
    427
    Joined:
    Oct 14, 2005
    Location:
    Calgary AB C
    Shooter:
    4x5 Format
    I got so frustrated with the styrofoam flaking I removed it from my Beseler mixing box.
     
  9. AgX

    AgX Member

    Messages:
    15,639
    Joined:
    Apr 5, 2007
    Location:
    Germany
    Shooter:
    Multi Format
    I too am very surprised for a fault at a diffuser to yield such result.