Mocon Concentrate - Update after one year in the freezer

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albada

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Long way to go? You just hot-mixed a developer based on glycol instead of water, which is a long way ahead of what most folks have ever done. Anyway, a test-roll carefully exposed and developed according to my instructions will confirm that the soup is correct. Then the fun begins...

Mark Overton
 

Steve Law

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I need to know how to use a densitometer and particularly a step wedge. Can I have some brief instructions on how to use these 2 items?
 
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albada

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Steve Law said:
I need to know how to use a densitometer and particularly a step wedge. Can I have some brief instructions on how to use these 2 items?
Click to expand...

For ordinary darkroom work, I believe these two are overkill. You are getting back into darkroom work, so you might want to just expose a roll at known exposures, and print them at grade 2 and see how things look. But if you really want to graph curves, here's what I did:

Densitometer: The "zero" button is most important: Position a clear section of neg over the light, lower the big lever containing the sensor, and press "zero" to make that spot read 0. Measurements you take on the neg of exposures of the wedge will measure density above base + fog. If you want measurements of absolute density, just lower the lever with no neg in there, and press "zero".

Using the wedge: I used a transmission wedge, which might have made things more difficult because I had to find a uniform and known light-source and back-light the wedge. I put the wedge in a black-painted box to block extraneous light to cut flare. A reflective wedge might be easier: Just meter the light (incident, or use a gray card) and take a pic of the wedge.

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Steve Law

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I have a reflective step wedge. Stouffer Opaque Gray Scale, 21 step with density readings and *L values written in. I think that might work. What do I do after taking the picture of the wedge?
 
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albada

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Steve Law said:
I have a reflective step wedge. Stouffer Opaque Gray Scale, 21 step with density readings and *L values written in. I think that might work. What do I do after taking the picture of the wedge?
Click to expand...

The picture will need to be close enough to the wedge so that its tiles will be large enough on the negative for the densitometer to measure them. Then you can plot the curve. I suggest setting the wedge on a dark or black background to minimise flare. Also, try taking two pictures of the wedge: one normal, and one with the lighter tiles covered with black paper. The second exposure will have less flare, helping the toe-area on the curve.

Mark Overton
 

Rudeofus

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Please note that Stouffer step wedges have significant dynamic range and that lens flare will change the exposure you get through the denser sections of your wedge. I recommend contact printing that wedge. Mark's method with double exposure may also work.
 
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albada

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Good points. In my tests, I used a 135mm lens (in 35mm format) stopped down a little to avoid fall-off, a prime of simple optical design (not a zoom) to minimise flare, baffling everywhere I could, including a draped black cloth between box and lens, and a slowish shutter-speed of about 1/8 sec to obtain the accuracy of electronic timing while avoiding mechanical inaccuracy. Double-exposing prevented the blast of light from the thin tiles from significantly flaring the dense tiles.

For best results, I'd want to contact-print, as both Rudeofus and Michael suggested. I've even mentally designed a mechanism for making a series of such exposures on a roll (each creating one test-strip). The tough part is providing uniform lighting at a short enough exposure-time to avoid reciprocity failure. I would use an array of LEDs controlled by a simple circuit, whose brightness is calibrated somehow... And as long as we're using LEDs, why use a wedge? Just make a series of exposures using LEDs of varying durations and brightness, each exposing a small circle on the neg. This would be a fun project, and maybe someday I'll have the time.

Mark Overton
 

Steve Law

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Mark wrote this in a previous post: "so you might want to just expose a roll at known exposures, and print them at grade 2 and see how things look."

This looks like something I could do without too much fuss.

So, what would I be looking for?
 

Rudeofus

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Steve Law said:
This looks like something I could do without too much fuss.

So, what would I be looking for?
Click to expand...

Subject matter you care about. What's the point of testing a developer for situations you don't care for?
 

Rudeofus

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albada said:
The tough part is providing uniform lighting at a short enough exposure-time to avoid reciprocity failure.
Click to expand...

So far I have used an enlarger, but even with shortest possible exposure times on this machine I think I run into reciprocity failure effects. Switching from Tri-X to Acros may solve my problem here. Another solution would be using a flash with a well designed softbox at a distance, this should give you both uniform and short exposure. I will also look at placing a strobe with radio trigger in my enlarger head.
 

Steve Law

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Minimum amount of developer for Mocon

Hello again,

Is there a minimum amount of developer (Mocon), that is needed to process a roll of 120 film?

Steve Law
 
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albada

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Steve Law said:
Hello again,
Is there a minimum amount of developer (Mocon), that is needed to process a roll of 120 film?
Steve Law
Click to expand...

Only the amount needed to cover the film in the tank. But if you're using a Jobo...
I've never measured minimum quantities, so I don't know how little you can get away with.
But the formula of Mocon is similar to XTOL diluted 1+1, so I don't think you want to be frugal with Mocon. I've developed a 36-shot roll of 35mm in 200 ml of Mocon, and that works out to about 45 square inches of film for each 100 ml of dev. You'll be safe if you don't go below 100 ml per 45 square inches of area being developed.

Mark Overton
 

Steve Law

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I measured 81.25" square for my 120 roll, so that means I can use 200 ml for a roll of 120 film in the Jobo. That'll work.

I have another issue. Right now everything in my place is at 72-75 degrees, including the Sulfite solution and the tap water. What would you suggest for temperature compensation? I am thinking something similar to what is laid out in the XTOL documentation.

Also, I have 4-5 thermometers and they all read differently. Where do I go to get an accurate thermometer?

Steve Law
 
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albada

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Here's a temperature compensation chart:
http://www.ilfordphoto.com/Webfiles/2006210208211880.pdf

Assuming that a thermometer is equally likely to be high or low, I suggest selecting the middle-valued (median) thermometer. Also, if a thermometer is off by 1 degree F, it would probably be difficult to see the difference. If you want to buy a new thermometer, I've found this $12 thermometer to be fairly accurate:
http://stores.photoformulary.com/thermometer-combined-scale/


Mark Overton
 

Steve Law

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shadows and highlights

Assuming the scene is exposed correctly, if I over develop, do the highlights have more density and do the shadows remain the same as if the roll wasn't overdeveloped? I am speaking in general terms and I think this is what I just did. I just need a mental image of what I am looking at.
 

Steve Law

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By the way, thanks for the time/temperature chart.
Steve
 

MattKing

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Roughly speaking, this is correct.

Assuming of course that the shadows are appropriately exposed. If they are over-exposed, the increased development will affect them in the same way as mid-tones - i.e. they will have some increased density as well.
 

Steve Law

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Thanks, I think the shadows were exposed properly. The highlights are not blown out, just a overdeveloped. I use a Yashica Mat 124g, so I am roughing it so far as exposure goes. I am trying to keep it simple. Again, thanks...

Steve Law
 

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Yesterday I found three small bottles of Mocon-X concentrate in the back of the freezer where they've lived at a nice cozy -6F (-21C) since I mixed the batch on 10 December 2014. It was only the palest yellow, so for giggles I shot a couple of sheets of FP4+ and tried it out - it worked just fine. That stuff is coming up on its 6th birthday!

Edit 12 Nov: The stuff in my freezer is/was Mocon, not Mocon-X.
 
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Donald Qualls

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Low temp and protection from oxygen is good for longevity of almost anything organic (and not living, of course).
 
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albada

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Mocon-X? I didn't know you had mixed that variant of Mocon. Like you, I have a bottle of the similar Mocon that's been frozen for about 7 years. I've used it for most BW rolls I've shot over that time, and the bottle is over half used.
It still works fine. But my bottle is still clear (no yellow), so I'm a bit surprised that yours has some yellowing.

Note that I am the inventor of Mocon. Here's my article from April 2013:
https://www.photrio.com/forum/resources/mocon-xtol-quality-in-a-long-lasting-concentrate.219/
I also put the article on my website:
https://fixfilmcamera.com/Mocon/Mocon.html
This article contains the formula, instructions, and discussion.

Mark Overton
 

Steve Goldstein

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You’re right, it was/is Mocon, not Mocon-X. Sorry, about that, I glanced at the article title just before I wrote that post and saw the "X" in XTOL, and my feeble mind thought it was part of the developer name. I guess I remembered that there was a Mocon-X variant further down the article. Thankfully the concentrate works better than my brain.

It was really hard to tell about the color, I think it was very slightly yellow, with emphasis on very.
 
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Rudeofus

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The idea behind Mocon is the solubility of development agents plus the alkali in Propylene Glycol. There is no easily available sulfite, which would be soluble in PG, therefore Potassium Sulfite won't help help in creating an one-component concentrate. It may be interesting to create a saturated Potassium Sulfite solution to make a second liquid concentrate component for Mocon.
 

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One interesting way to potentially get sulfite into a water free solution is that metabisulfite is "noted" (wikipedia and elsewhere) to be somewhat soluble in glycerol. However, I took some glycerol up to 180F and never did seem to get much, if any into solution. Glycerol might come with it's own problems though, not to mention it's especially thick

edit: the HC-110 way that's unapproachable for home chemists without a fume hood is I believe the reaction of sulfur dioxide (gas) and triethanolamine. I do wonder if there could be some "dirty" way to synthesize it by producing sulfur dioxide in solution, like by reacting metabisulfite with a non-aqueous acid, but the natural alkalinity of TEA seems to prevent that
 
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