The Problem

I’ve had a really persistent, aggrivating problem lately. I keep getting light-colored blobs at the top of my negatives, consistent with the “up” direction in the developing tank:

The negative
And here’s what it looks like in the scan, bass-boosted so you can see them more clearly

What’s going on?

There are a few things we can deduce from the clues on the negative:

  1. The spots are less dense (lighter) than their surroundings, pointing to a case of under-development
  2. The spots do not continue outside of the exposed area, meaning that these are likely not light leaks from my camera or a loose roll
  3. They’re all on the same edge, and they’re bubble-shaped

This stuff led me to believe that I’m getting persistent air bubbles between the negative and the top of the developing reel:

Right here, but on the flipside of the film, inside the curve

This really stumped me at first, since I’ve been developing my B&W film the same way with the same equipment for a little over a year, and these just appeared out of nowhere.

I asked /r/AnalogCommunity about the issue, and I got a few great suggestions that I’ll talk about in the next section. But the root cause seemed to be some sort of coating or finish degradation on the plastic Paterson reels I’ve been using.

What did I try?

Various combinations of the following:

  • Mixing wetting agent with my developer to try and break the surface tension and prevent bubbles
  • Bonking the tank on the counter really hard immediately after filling. I’ve always made a habit of tapping it frequently during development, but I tried being really aggressive about it
  • Using 100ml more developer than I normally do in hopes that the extra water pressure would force the bubbles out

The Solution

Per the suggestion of the random person on Reddit, I tried switching to stainless steel developing equipment:

Hewes 120 reel and Kalt tank

And it worked great! I’m getting consistent results again. The smooth steel plays nicer with the Rodinal developer I use most of the time. The tank is also much smaller than the Paterson one, meaning less chemicals per batch, plus the reel is super solid and loads much easier than the plastic ratchet ones.

There are a few caveats, though: the steel tank leaks. Not a lot, but maybe a drop each time I invert it. Also, the Hewes 120 reels are surprisingly expensive (~$65 each), though allegedly they’re indestructible and you can hand them down to your grandkids if film is still around in 2060. Even despite this stuff, I’m really satisfied with the results and am a true stainless steel believer now