Surge marks

Owned by Uneven Development, Bromide Drag and Surge Marks, which puts this at the over-agitated end of the lever that produces drag at the other, and which records the same sourcing gap this entry does: Kodak’s table has the category, streaks of non-uniform density against excessive or uneven agitation, and no manufacturer publication in the corpus names the sprocket-hole mark specifically, so the flow-through-the-perforations account is mechanism rather than citation. This entry came from diffusion, swelling and the journey into the emulsion before that page was written.

What you see

A regular series of marks along the long edges of a 35 mm negative, aligned with the perforations and repeating at their spacing. The emulsion beside each hole is denser than the emulsion between them.

The regularity is the diagnosis. Nothing else in the processing chain repeats at a fixed pitch determined by the film’s own geometry.

Likely causes

1. Excessive agitation.
2. Uneven agitation — a rhythm that drives solution the same way every time.
3. Inversion that is too vigorous, so that flow through the perforations dominates flow across the face.

What is happening: the chemistry and physics

Development is transport-limited at the emulsion surface. The developer immediately against the layer is being consumed, and the whole function of agitation is, in Kodak’s own words, removing exhausted solution from the emulsion surface and replacing it with fresh.

With 35 mm film in a spiral tank, agitation drives solution through the perforations, so the emulsion beside each hole is resupplied more vigorously than the emulsion between them, and develops further. The result is a regular series of marks aligned with the holes.

!What is sourced here and what is not

The course states the mechanism as the flow argument above, and it has not found a manufacturer publication naming the sprocket-hole surge mark specifically. The attribution is therefore presented as mechanism rather than as a sourced identification, and this entry inherits that.

What manufacturers do document is the category. Kodak’s troubleshooting table lists “streaks of non-uniform density” against “excessive or uneven developer agitation”, and “mottle — areas of non-uniform density” against “inadequate developer agitation”. Both entries are about unevenness and they point in opposite directions.

Diagnostic questions

• Do the marks repeat at the perforation pitch? Measure it. This is the observation that separates surge marks from every other streak.
• Are they at the long edges, encroaching inwards? They should be, because that is where the perforations are.
• How was the tank agitated? Kodak’s published small-tank procedure is 5 to 7 inversion cycles in 5 seconds, repeated at 30-second intervals. More vigorous than that, or more often, is the suspect.
• Is this too much agitation or too little? Streaks with a direction and a pitch are too much; general blotchiness with no direction is too little, and streaks running downwards from the dense areas is too little as well. Three faults, one lever, three directions.

Corrective action

None on the negative.

For the next film, moderate the agitation to a published procedure and change nothing else, so that the result is evidence rather than a new guess.

Prevention

Agitate to a written script and use the same script every time. A script is what makes agitation a controlled variable rather than a mood.

Vary the direction of inversion rather than repeating one motion, so that no single flow pattern is reinforced over the whole development.

Record the agitation script in the processing log with the times, because a negative whose log says “agitated” cannot be compared with anything.