What chemical for anti reflection coating that dissolves completely?

Discussion in 'Silver Gelatin Based Emulsion Making & Coating' started by rwhb12, Mar 16, 2013.

  1. rwhb12

    rwhb12 Member

    Messages:
    36
    Joined:
    Dec 31, 2012
    Location:
    Kettering, U
    Shooter:
    Medium Format
    I have always wondered what is used on film backing as it liquefies completely in contact with water, leaves no stain or residue, yet must do a good job of preventing light piping and reflections. Can someone enlighten me?

    Russ
     
  2. Gerald C Koch

    Gerald C Koch Subscriber

    Messages:
    7,766
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    Do you mean the anti-halation coating?
     
  3. AgX

    AgX Member

    Messages:
    14,477
    Joined:
    Apr 5, 2007
    Location:
    Germany
    Shooter:
    Multi Format
    Well, the antihalation coating is an anti-reflection coating, with halation being caused by reflection.
    Though it can serve other purposes too.

    Several different systems are employed. Furthermore aside of a coating of the backside of the film base a coating inbetween the film base and the emulsion is employed
     
  4. Gerald C Koch

    Gerald C Koch Subscriber

    Messages:
    7,766
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    Light piping is caused by light entering the edges of the film base. This is a problem with 35mm file but not other formats. To prevent this a dye is encorporated into the film base. This dye does not wash out as it is part of the plastic base. The amount of light piping is a function of the type of plastic. Estar (Kodak tradename for polyester) based film is more prone to light piping than is acetate based film.
     
  5. OP
    OP
    rwhb12

    rwhb12 Member

    Messages:
    36
    Joined:
    Dec 31, 2012
    Location:
    Kettering, U
    Shooter:
    Medium Format
    Thanks for replies so far.
     
  6. kevs

    kevs Member

    Messages:
    544
    Joined:
    Aug 21, 2006
    Shooter:
    Medium Format