The curse of drip marks

[tim_bradshaw1]

<p>I've recently gone back to processing & printing my own film after a long time (20 years) not doing so. I'm doing this in a shared darkroom using their chemicals etc. Mostly it has been a good experience, but I am cursed by drip marks, particularly on 35mm (120 seems better, I am not sure why - drips are not just less obvious because comparatively smaller, but there are really less of them). My washing & drying process is:</p>

<ol>

<li>initially do a couple of complete fills & empties of the tank to get rid of the worst of the fixer;</li>

<li>wash for 15 mins or more with running water down spine of tank in usual way;</li>

<li>empty tank;</li>

<li>couple of drops of wetting agent, fill tank, invert a couple of times, leave for 2 minutes or so;</li>

<li>empty tank, open, give film (in spiral) a good shake to get water off it;</li>

<li>take film out of spiral, don't squeegee it, but possibly (tried a couple of times) remove water by running through (clean!) fingers;</li>

<li>hang film to dry in cabinet overnight (no hot air, just room temperature).</li>

</ol>

<p>And ... drip marks. So what am I doing wrong? The things I can think of are</p>

<ul>

<li>Maybe the wetting agent is crap and I should buy some (I will do so anyway)?</li>

<li>Should I squeegee the film? I remember this being a sure way of getting scratches.</li>

</ul>

<p>I think I vote for the wetting agent being crap, but I'd be really interested in any other ideas. I've heard people say "use distilled water for the final rinse", and that would be great but I have a lot of film to process and I probably can't afford that.</p>

<p>A related question: what's the best process for rewashing film (in strips). I'm thinking of just curling it up and putting it into a tank to wash, but I can't see this being other than very fiddly. Fortunately, as usual, the drip marks show up less on prints than you might think.</p>

[bgelfand]

<p>For your final rinse with wetting agent, use distilled water. Drip marks are nothing more than particles suspended in the water that are left behind when the water evaporates. If you reduce the particles, you reduce the drip marks.</p>

[tim_bradshaw1]

<p>As I said: I'd rather not have to buy and cart around vast quantities of distilled water which I would rather not do (I'm also already in a fairly soft-water area). I also don't think it's really the problem: the problem is that when a drip dries it dumps all the crud in a ring due to some surface tension effect: a wetting agent ought to fix that so that the drip shrinks as it dries, leaving an imperceptible mark. What I don't understand is why that's not working for me given I am using a wetting agent.</p>

[thirteenthumbs]

<p>The drying marks are likely due to using insufficient wetting agent. I use an eye dropper that holds 1cc/ml liquid and use .75 ml Photo flow per 1500 ml water where I currently am. The water used in the final rinse determines the amount of wetting agent needed. Some areas I worked in required 2 ml wetting agent per 1500 ml water.</p>

<p>Increase the amount of wetting agent you are using in small increments (+25%) until the drying marks disappear.</p>

[leighb]

<p>Where's your hypo clearing agent?</p>

<p>With PermaWash you only need to wash a couple of minutes in running water, then a couiple of miniutes in PermaWash<br /> (no running water), then wash another couple of minutes in running water.</p>

<p>Final rinse for ~30 seconds in PhotoFlo (no running water) at the reecommended dilution (1:200 or whatever).</p>

<p>PhotoFlo is just soap. It breaks the surface tension of the water and allows it to drain off.</p>

<p>I never have any water spotting issues.</p>

<p>- Leigh</p>

[jim_jones3]

<p>I'm with Leigh. My well water is bad, so distilled water is used to mix chemicals and for the final rinse with Photo-Flo diluted somewhat more than Kodak reccommends. A couple of drops isn't enough. The final rinse can be reused, although contaminates will gradully build up. Thoroughly draining the film before the Photo-Flo bath will reduce this buildup. Squeegeeing the film is risky.</p>

[Alan Marcus]

<p>I am not an advocate of distilled water. Most prepared formulas for developer and the like are formulated to be mixed in potable water. Most contain trace amount of water softeners and chelation agents (proprietary stuff). The use of distilled water in most cases will do no harm but likely does no good. Water from your local municipality is likely good enough, filtering won't hurt a bit. </p>

<p>Drying marks can be caused by particulate matter on the film's surface but more likely --- water droplets that remain on the film during the drying stage alter the shrink rate of the gelatin binder. Modern films used gelatin as the glue to hold the light sensitive goodies on the film base.</p>

<p>When the film is dunked in the developer, the waters of the developer cause the gelatin to swell much like a dry sponge plunged into water. This swelling opens up the gelatin structure allowing the fluids of the process access. After the process is complete and residual chemicals flushed out or neutralized, the film is plunged into a surfactant. This agent causes the water to sheet and not bead. This is the stuff of uniform drying.<br>

During the drying cycle, the gelatin shrikes back to the original thickness. Should beads of water remain on the film's surface it retards drying and thus alters the shrink rate in localized areas. The film under the water beads will not have the same thickness as the surrounds and likely never will. This is the stuff of drying marks.</p>

<p>The concentration of the surfactant (PhotoFlow and the like) is critical. Good technique requires careful measurement and inspection before drying to make sure beads of water are not standing on the film. </p>

[lex_jenkins]

<p>Suspend the film diagonally to dry. Water gravitates toward the lowest single edge and drips off a single corner. Any water marks will be confined to the film rebate where it won't matter.</p>

[ian_gordon_bilson]

<p>The whole point of wetting agent is to have enough to do the job. And not too much.<br>

The distilled water thing is a waste of time,and distilled water. If the W/A is strong enough to do the job,the final rinse water will "sheet off" the film,carrying deposits & crud with it.<br>

This is why it is recommended. My water is worse than many,but,if you get the W/A ratio correct, your film should dry without crud.<br>

If too much,you may get shiny spots,on the base side of the film - easily removeable after drying with a breath of air,and a light polish with a soft cloth.<br>

Use a bit more WA until it works properly.</p>

[tim_bradshaw1]

<p>Thanks for the replies. I am going to (a) buy my own wetting agent and (b) be more organised about measuring it (get a syringe, I think). I'm really doing (a) only because I live in fear of what might be in the containers provided by the place I'm processing films - the place is very good, but not all the other users are as careful as they might be.</p>

<p>(Someone will say: "why are you worrying about wetting agent when there could be anything in the dev/stop/fix bottles?". Good point.)</p>

[lex_jenkins]

<blockquote>

<p>"The distilled water thing is a waste of time..."</p>

</blockquote>

<p>Depends on your water supply. When I lived in a rural area with well water our wells were in limestone basins. Even with filters there was a lime residue on everything. I used distilled or bottled water for all film chemistry mixing and washing.</p>

<p>With a city water supply I still use distilled or bottled water and a drop of wetting agent for the final rinse. With the Ilford in tank method it's economical. Our city water is reasonably good but between the city and building pipes there's some residue around drains.</p>

<p>I've found wetting agent to be less a factor when suspending the negative strips diagonally. I still use it but probably could do without it.</p>

[michael_josefsson]

<p>Am reading this with great interest as I also have succumbed to the dreaded marks. About the squeegee: It sounds great in theory (and perhaps it really is great in theory) but as it is a scissor-like rubbery thing it almost never squeegees the entire film in one go. The film edge closer to the joint will get wiped but the other side almost never:( On 120-film at least I have stopped using it, the risk of marks far outweighs its benefits.<br>

There are boilers for making ones own distilled water.</p>

[mukul_dube]

<p>If your water is not hard, correct use of wetting agent should do the job. Suspending the film diagonally is the best answer, but it is not so easy to do, specially with many rolls.</p>

[chris_douglas1]

<p>I'm with Lex, it depends on your water. The water here is so hard, a new shower head lasts a couple of months. I use all distilled water, and 1ml photoflo to 500 ml water, and hang at a 45 degree angle like the others. Any tiny bubbles or debris runs to the edge and drains off the bottom corner.</p>

[jpo3136b]

<p>Wait about 10 minutes after rinsing and inspect the film. The emulsion won't have set hard yet. If the film is drying unevenly, it'll be easy to tell; you'll see a color difference in the dried and still damp areas. Maybe rinse again if you think the drying will leave a mark. Most of the time when you get in a jam, another water rinse for a minute won't be detrimental.</p>