Sticky residue on negatives

[brunomorez]

<p >I developed some 35mm Tri-X last night. After letting the negatives dry for 3,5 hours, I noticed a clear sticky residue where you'd expect the last droplets of water on a negative when leaving it to dry. It's odorless but it makes the negatives stick to their storing sheets.</p>

<p >This is the first time I've experienced this (in say 70 developments). I'm thinking this is some kind of contamination, but I'm not sure where it comes from.</p>

<p >Here's my development proces;</p>

<p >Using a Patterson plastic 2 reel tank</p>

<p >Develop in Rodinal 1:50, using tap water that has been boiled. I've been experimenting with distilled water as well, but the mineral content of the tap water seems to make the Rodinal more active. If I use similar times with distilled water, my negatives look flatter and more grey.</p>

<p >Stop</p>

<p >Fix: Ilfofix 1/10, fresh stock, tap water</p>

<p >Rinse: Ilford method (5,10,20,40 inversion) with standard tap water</p>

<p >Final rinse; a 10 minute soak in distilled water with a few droplets of Amaloco H10 wetting agent.</p>

<p > </p>

<p >Then I swing the reel around to get rid of extra water on the negatives and hang them to dry. I cut my negatives when they're wet, because this seems to make them less prone to 'convexing'.</p>

<p >One thing I never do is thoroughly wash my tank, reel, etc. Could it have something to do with this?</p>

[larrydressler]

<p>Sounds like wetting agent build up. Scrub your tank and reels and back off on the amount of wetting agent you use. I always use 1/2 what kodak post for photo flo. 2 drops may bee too much for you.</p>

[frank.schifano]

<p>First of all, you really should make sure your tanks and reels, and everything else, is cleaned up before you're done. Not doing that is asking for trouble down the line. Whether or not this is the specific cause of the problem you're describing here is unknown.</p>

<p>Second, why are you cutting up the negatives before they're dry? That's asking for more trouble. The gelatin emulsion is fragile when wet and should be handled as little as possible. Once dried it is far more robust.</p>

<p>There's no need to soak the film in wetting agent for 10 minutes. A quick dip is all you need, and you might be using too much wetting agent. I don't care what brand you're using, they're all pretty much the same. Use only enough wetting agent to prevent the water from beading up and NO MORE. The amoundt required to achieve that varies with the water supply, so some experimentation is needed to determine the amount you need to use.</p>

<p>Finally, I really think your problem is that you haven't allowed the negatives to dry fully before putting them away. Excess wetting agent can do that. Drying time is highly dependent upon the atmospheric conditions of the drying space. If it's humid, the drying process will take longer. If the air is dry, the time will be shorter.</p>

[Alan Marcus]

<p>Municipal water supplies receive their water from ground sources where the water percolates through limestone and other mineral deposits and thus contains calcium and magnesium. This is the stuff of hard water. So-called Temporary Hardness can be reduced by boiling as this process causes some of the minerals to fall out of solution forming calcium and magnesium carbonates that are insoluble thus they can be filtered out. This method can reduce the formation of scum.</p>

<p>Some water supplies contain anions of chloride or sulfate and these cannot be removed by boiling. This type of contaminate is called permanent hardness. In addition, you should be aware that municipal water supply sources often undergo seasonal changes, as often the municipality will switch to a different source based on availability.</p>

<p>If you are having troubles and believe the water supply is the problem, first switch to a bottled water to see if that will restore your process. If bottled water fails, switch to demonized water available at most druggists and large food stores. Lastly, switch to distilled water. Seems like weird advise? Most prepackaged developers and secondary chemicals of the photo process anticipate that the user will mix in ordinary tap water. The manufacture thus adds proprietary ingredients to do battle with hard water. These are surfactants that reduce surface tension and calgon that precipitate minerals. There are many other additives. Distilled water is known in chemistry as "hungry water" it is very reactive thus, it sometimes causes problems. One would think that distilled water is best but this is not always the case.</p>

<p>The following is not your problem, as the fix you are using contains no hardener. Fix solutions often have a hardener additive to help prevent the gelatin of the film and print from abrading. Of the two hardeners in general use, the most common is potassium alum followed by chrome alum. Now most fix baths are acid to help neutralize developer carry-over. Thus, the PH of the fix is likely between 3.1 and 3.8. Should the fix contain chrome alum and should the pH drift out of this range, a heavy gelatinous precipitate forms.</p>

<p>Of all the steps you describe, the one I do not like is the long soak in a wetting agent mixed using distilled water. Cut this to 30 seconds or at most a 60 second swish. The sticky deposits are likely gelatin. Consider using bottled water or filtered tap water for the final rinse. Maybe you should try a hardening fixer as this will prevent the film gelatin from getting too soft. </p>

[brunomorez]

<p>Great answers, many thanks!</p>

[chris_douglas1]

<p>That happened to me once when I accidently mixed my photofo 20:1 instead of 200:1. It looked like little beads of sweat. Now I generally mix 500:1 and hang negatives at a slant so the water flows to the lower edge and runs off outside the exposures. I use no sponges, squeegees or finger "squeegees". No scratches or spots, yes!</p>

[mjferron]

<p>Bruno is it as simple as the last remaining drops are not dry? I hang my film like yours. When I test I slide my fingers over the blank film at the low end. Often depending drying conditions those areas at the bottom where the last drops hide out take a while longer to fully dry.</p>

[brunomorez]

<p>At first I thought it were drops of water, but when I touched one I noticed they were sticky and jelly-like.<br>

I'll use bottled water for my next development, in a clean tank, and only a 30 s dip in the final rinse in either distilled or bottled water.</p>

[Alan Marcus]

<p>Gelatin is the binder that glues the light sensitive silver salts onto the film base. Gelatin is used because it is transparent, flexible, has a low solubility and expands when wet in the engorged state. Now fluid can penetrate and percolate through its structure allowing the chemicals of the process to reach the sliver salts. Before gelatin, egg whites were used. No suitable substitute for gelatin has been discovered. Mainly because gelatin was found to somehow interact with the silver salts boosting the emulsion's light sensitivity. Now we know it is impurities in the gelatin animal product that does this trick.</p>

<p>When film is immersed in the fluids of the process the gelatin expands much like the action of a dry sponge. When hung up to dry the gelatin shrinks. If water droplets are allowed to remain on the film during the drying stage, the shrink rate of the gelatin under the droplets is slowed. The area under the drop will eventually dry and shrink but that area will not match the elevation of the surround. This is the stuff of water spots. Most would think a film with water spots is marred due to a higher concentration of mineral residue and this might be true but more likely it’s the uneven shrink rate that you are seeing. The swell / shrink rate is effected by minerals in the wash water. Distilled water yields the highest gelatin swell, hard water the least. Distilled water is "hungry water" meaning it is highly reactive. While the gelatin has low solidity, some will dissolve and this is accelerated if the water is reactive. The sticky stuff you feel in the water droplet is dissolved gelatin. </p>

<p>The countermeasure is to use a hardening fixer and a quality wetting agent. The hardener toughens the gelatin reducing its solubility. The wetting agent is a surfactants that break the surface tension by disrupting the water air interface of water causing the water to sheet impeding droplet formation. Kodak's FotoFlow is the old reliable. </p>

[brunomorez]

<p>Developed in bottled water yesterday in clean recipients, tank etc.</p>

<p>Rinsed for 60 secs in distilled water, had some small water spots though, so a 2 minute rinse might be better. No sticky residue though.</p>

<p>Thanks for all the sound advice once again.</p>