damaged emulsions (pockmarks?)

[rjjackson]

<p>hi,<br /> i have a problem with some films that have little pockmarks or perhaps "pinholes" in the emulsion. it looks like the gelatin is just missing, as if some insect ate it or some acid was poured on it and burned little holes in it. i have never seen this problem before and it just occurred on two films very badly and a few others as well but more slightly. i'll give more details below. <br /> <br /> one film was p-x, the other hp5+, both stored and carried in different conditions, though possibly subjected to heat around 40 degrees for a day or so (but not left in a car).<br /> <br /> the chemistry is d-76 mixed about 2 months ago and stored in air tight bottles until i used it a few days ago. the fixer was 1:9 ilford rapid.<br /> <br /> the first bath of development got fresh fixer and showed no problems. the second two batches showed problems and got fixer once and twice used, the second one being replenished with about 25ml to 1 liter.<br /> <br /> not all the films in the second and third batches were affected the same way and films in the same tank were affected differently. two different films/processing days got the marks very badly. one was processed alone (p-x), the other (hp5) processed with a roll of 5222 in the tank (which shows almost no damage). the other films from the second and third batches of fixer use show very slight pockmarks, i even didn't notice on them until looking with a loupe (and they appear only rarely and very small), but in any event they are present in the second and third fixer batch and not in the first. <br /> <br /> <br /> i have some hypotheses but i'd like you guys to look over my workflow to see if you can isolate some problem i'm not seeing.<br /> <br /> 1. oversoaked gelatin, either during presoak or in fixer?<br /> 2. over agitation during bath or in fixer? <br /> 3. high temperature differential between development and rinsing bath (perhaps 5 degrees sudden change)?<br /> 4. perhaps a combination of 1 and 2?<br /> 5. d-76 went bad? <br /> 6. heat damage?<br /> <br /> here is a detailed description of my workflow:<br /> <br /> --stock chemicals stored in freshly emptied waterbottles (stored in dark closet temp, 25 degrees).<br /> <br /> --to make working solution, mixed with tap water that has been frozen and thawed in ice bucket to produce 1:1 working solutions (usually comes out at 15 degrees, then i put it in bucket of warm water to slowly bring it up to 19 degrees).<br /> <br /> --film is loaded in clean tanks.<br /> <br /> --presoak films in tap water while mixing solution (between 2 and 5 minutes, 3 or 4 rinses).<br /> <br /> --development starts at 19 degrees and usually finishes around 22 degrees (dev times usually between 10 and 15 minutes).<br /> <br /> --agitation continuous for 30 seconds for push and 60 seconds for pull, plus two inversions per minute.<br /> <br /> --no stop bath, two quick rinses in tap water (about 24 degrees).<br /> <br /> --fixer stored in closet (working solution 1:9, about 25 degrees).<br /> <br /> --fix for between 5 and 10 minutes (10 if i am tied up with a second batch, shoot for 5)<br /> <br /> --rinse in tap water for not less than 10 minutes, sometimes 15 or 20. <br /> <br /> --add some flow agent, agitate and soak for about 30 seconds<br /> <br /> --dump water and add distilled water, agitate for 1 minute<br /> <br /> --dump and add 2nd bath distilled water, let sit for 1 to 3 minutes<br /> <br /> --shake films off in the reels, disassemble reel and hang to dry<br /> <br /> --no use of squeegee or at any time do i touch the emulsion.<br /> <br /> here is a scan from one negative showing the pockmarks (100% crop from 6x6 neg scanned at 1800 dpi). i want to emphasize that these are not dust spots but holes in the gelatin:<br /> <br /> http://rjjackson.com/images/pocks.jpg<br /> <br /> i would be grateful for any help on where to start sorting out this problem.<br /> rj</p>

[Ed_Ingold]

<p>I've encountered bad film. The usual problem is incomplete coverage, or pock marks which are formed by bubbles in the gelatin. The appearance of your sample is not consistent with these observations.</p>

<p>Two months is a long time for developer. Plastic bottles are not air tight - they are fairly permeable to oxygen - the nemesis of developer. Use glass bottles for long-term (> 1 week) storage). If you mixed the developer using tap water, there may be particulate in the water, or due to chemical interactions. Check the stock solution for particulate (and discoloration). Do this also with the fixer. Fixer is notorious for producing particulates with age or improper mixing.</p>

<p>There may also be a chemical reaction with the fixer, which is acid. Besides stopping development, they provide a milder neutralization than from the fixer, and minimize depletion of the fixer (which can result in the formation of particulates).</p>

[rjjackson]

<p>edward, thanks for some ideas.<br>

i usually check for particles in the chemistry. the d76 is clear and clean, the fixer was mixed fresh from stock (though not the newest bottle). i always make stock with distilled water but make my working solution with tap water. maybe i'll change this to distilled. i'll try again with everything fresh, i even bought new fixer, but it'd be nice to understand what caused this. i've never had a problem with 2 month old developer before and even have used far older stock than that for test strips with no problems.<br>

by incomplete coverage, do you mean that the developer didn't reach all of the emulsion? it's possible that my tap introduces lots of bubbles during my rinse but i shake it up several times and give a good agitation with taps for bubbles. if anything, i worry that i'm over agitating.<br>

let's suppose bubbles form in the gelatin and burst at some point -- can you think of something that might be creating these bubbles?<br>

here's a snap from the digi of the surface of the emulsion, showing that indeed they are pocks and not particulates suspended in the emulsion.<br>

http://rjjackson.com/images/pocks2.jpg</p>

 

[randrew1]

<p>I don't know what caused the defects, but I'm sure the defects happened sometime after the film was coated. Coating defects have some alignment with the coating direction.</p>

<p>Two <strong>possible</strong> causes to add to your list:</p>

<ul>

<li>bugs that eat gelatin--it happens</li>

<li>emulsion pickoff. Are there any bits of gel stuck to the backing? Sometimes moist emulsion will stick to the back of another layer when the film is wound up. </li>

</ul>