Why is black sediment forming in the bottom of my film developer tray?
Asked 4/27/2017
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I’m developing sheet film and noticed a fine black sediment collecting at the bottom of the tray. I’m using Ilford HP5+ and Delta 100 in ID-11, reusing the developer for several sheets but staying within the recommended capacity. Development appears normal, and the sediment stays at the very bottom and rinses out easily when I pour the developer back into its bottle.
I tested the film base separately: water loosens the antihalation backing and produces a black residue when wiped, but developer seems to dissolve or change that layer without leaving visible residue. So I’m wondering whether the sediment is actually from the antihalation layer, or if it’s more likely some kind of precipitate from the developer or water.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
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The developer solution is somewhat complex as to the reactions occurring. All commercially available formulas add proprietary goodies to combat hard water. Often, dissolved minerals from the water will precipitate out of solution. All water contains dissolved oxygen (the developer is mainly water). The developing agent has an affinity for oxygen and this reaction destroys the developer. The developer is a derivative of benzene which was initially extracted from coal (now likely synthesized). As the developer reacts with oxygen, the developer reverts to coal tar.
All formulations contain a preservative which is sodium sulfite. The preservative reduces aerial oxidation and reacts with oxidized developer to render it non-staining. After a time, the preservative is exhausted and gives up. We replenish developers with a modified formula that rejuvenates. Other solids will precipitate out of solution especially when the developer is near exhaustion.
Most films sport an anti-halation coat made of dye. Some motion picture films are back coated with a Rem-Jet (removable jet black) make of lamp black. The Rem-Jet is held in an acid plastic that releases in an alkaline solution. It is not likely that the sheet film you are developing has a Rem-Jet.
Originally by user44949. Source · Licensed CC BY-SA 4.0
user44949
9y ago
0
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It’s probably not the antihalation layer. Based on the responses, the more likely cause is developer byproducts or mineral precipitate from the water supply.
ID-11 contains developing agents and sodium sulfite preservative; as the solution ages and reacts with oxygen, oxidation products can form. Hard-water minerals, especially calcium salts, can also react with developer ingredients and create insoluble sludge or sediment. That can show up as fine dark silt in the tray or bottle even when the developer still works normally.
If your negatives are developing properly and you’re within the recommended reuse limits, a small amount of sediment is not usually a serious problem. If you want to reduce it, try mixing chemistry with distilled water. You could also presoak the film for a couple of minutes so any antihalation dye washes out before development, though opinions on presoaking vary.
In short: black sediment in reused ID-11 is most likely precipitate/oxidation products, possibly encouraged by tap water minerals, rather than damaged film or a major processing fault.
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