what is bromide drag? And how can I fix it?

Discussion in 'Black and White' started by brian steinberger, Aug 6, 2006.

  1. I have heard of bromide drag, and I think I encountered it tonight. I had an
    image with a nice clean sky and I scanned the negative and you can see
    differences in density across the sky. I am developing 6 4x5 negatives at a
    time on hangers in 1/2 gallon tanks. What can I do to solve this problem?
    I'm agitating continuously for the first 30 sec. then once for 10 sec every
    minute, using lift, tilt to one side, replace, lift, tilt to oppisite side,
    replace, lift and drop.

    Brian
     
  2. It's a streak down the negative. I belive a presoak can usually take care of this.
     
  3. Bromide is by product of development. If there are areas of high development, the bromide runs down the neg causing uneven density. The fix is more agitation.

    if the sky was in the lower part of the holder and the streaks match up with the drain holes in the holder, it was caused by developer flowing very fast thru the holes and saturating the emulsion in a local area faster than the rest of the neg.


    The fix is more initial agitation, 4 lift and drain cycles in the first 30 sec or better yet, 8 lift, tip, drain, cycles in the first minute.

    Going slow imersing the holders will not cure the drain hole streaking.

    Drain hole streaking needs to be fixed by initial agitation, but if that does not cure the problem, use a water presoak and extend the time 5/10% and / or dilute the developer.

    Proper agitation is 30/60 sec on imersion and TWO out, tip, drain, reimerse cycles in 10 sec done every minute.

    All this is tough with 6 hangars in 1/2 gal rubber tank. I can`t do more than 4. A hangar rack that holds 8 or 20 hangars in the 1/2 gal or full gallon stainless tank makes management easier. the hangars are held tightly in an open box and do not splay apart at the bottom.
    Arkay Corp in Milwaukee. And the rack will not fit the rubber tanks.

    $200 for a rack and single tank. Dirt cheap if used. They made a water bath/ chiller box that holds 3 tanks that would be nice to have. Mine came free from a neighbor, but had to buy one replacement tank and hangar rack. There are also 5x7 one gallon tanks and even larger ones for 8x10.
     
  4. Evidence of "bromide drag" can be described by "comet tails" slightly seperated from sprockets holes and sometimes high density images. It is the result of bromide migrating from the film emulsion to the developer and "killing" the activity level of the developer. When the bromide overpowers the developer, especially a highly diluted or weak developer, then bromide drag will appear. Solution; use a better developer.
     
  5. I used fresh D-76 1:1 las night. So the developer was fairly strong. So that couldn't have been it.
     
  6. Bromide will overcome fresh full strength developer with insufficient agitation.

    This can be only two things, bromide or the drain hole problem above.
     
  7. Forget the tilt-tilt business, it does very little to aid agitation. It's lifting the film out and re-immersing it that agitates the bath. Just think about professional gas-burst agitation, which is very efficient. Where does tilting and draining come into that? Nowhere! Why? Because creating turbulence in the developer is what counts.

    Just increase the number of lifts per minute to two, and you'll be fine Brian.

    Another cause of uneven density could be air bubbles sticking to the film surface. This can be prevented by a slower initial immersion, and by knocking the film cage on the bottom of the tank after immersing it.
     
  8. It could be a scanning problem. What bit depth did you scan the negative? It's usually best to scan negatives in color at the highest bit depth available. Low bit depth can result in posterization (abrupt changes in density) in smooth areas like sky.

    'I scanned the negative and you can see differences in density across the sky.' sounds like posterization. I think you are limited to 16 bits or less in BW,depending on your scanner, but some scanners will let you do 48 in color. You can convert to BW after you've tweaked the image in *****shop or other application.

    Print the neg or check it on a light box. If it looks like the print, it's the negative. If it looks smooth, its the scanner or scanning technique.
     
  9. I'd suggest one agitation every 30 seconds after the initial 30 seconds of continuous agitation.
     

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