Streaks on negatives

On occasions after processing negatives (usually T Max ut not always) there are marks running accross the film usually from sprocket hole to sprocket hole. Any clues?

This is a guess. Fixer that hasn't been agitated thoroughly enough sat in the film and rubbed out parts of the emulsion.

Sounds like a twiddle stick problem to me. When you agitate, do you use the twiddle stick? This can cause uneven development. In that case, try inverting instead.

First, check your agitation. Is it up & down? This would cause the chemistry streak in the pattern you mention. Across the film from sprocket hole to sprocket hole. If you raise & lower the film in chemistry for agitation without 'twirling' it or changing your routine you will get chemistry flowing the same way every time. This will cause density differences in a pattern as it sounds you are getting here.

Streaks on the negative happen during the first min. or so of development and are caused by either to much or to little agitation. In most cases it is the former. Try using a more even and softer first and second agitation method on a few test rolls and see if that helps. Streaks are something that we all get, weither we see them or not. They are more noticed in clear areas (skys,etc.). But if you were to measure all your negs under a densitometer you would find that almost all your negs had some buildup on the edges. Its he nature of the beast.