Analyze this: DK-50 v. 48M

Michel Hardy-Vallée

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In reading good old Kodak and Agfa/Ansco formularies, it dawned on me that many formulas are pretty much the same between manufacturers, but there are some minor differences.

Exhibit no. 1 is Agfa 48M (metaborate developer) and Kodak DK-50. Both are very similar formulas, except for the MQ ratio and the amount of sulfite:

48M
2g metol
40g sodium sulfite anhydrous
1.5g hydroquinone
10g sodium metaborate
0.5g potassium bromide
Water to make 1L

DK-50
2.5g metol
30g sodium sulfite anhydrous
2.5g hydroquinone
10g sodium metaborate
0.5g potassium bromide
Water to make 1L

And before you tell me "you just have to try them out" to understand the differences, I'm asking those of you who have some inklings of chemistry or who would like to wager a hypothesis. After that I may indeed try to compare them, but I want at least some idea of what I should be looking for.

Here's what I understand: normally, the MQ ratio is a sign of activity, so if you have twice the hq than metol, it's going to be a more active developer than one with a 1:1 ratio metol:hq. Sulfite does many things, but it's a preservative so it helps maintain the activity of developing agents, like hydroquinone.

So all I can figure out is that the MQ ratio of 48M makes it less active than DK-50, but the higher preservative amount would compensate for this reduced activity? Also, finer grain because more sulfite? What do you think?
 

voceumana

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The greater levels of metol and hydroquinone would make DK-50 more active. DK-50 was recommended for full strength as well as 1:1 dilution. I think the Ansco was just recommended for full strength use. The sulfite level difference might not be enough to make much of a difference.

Consider that their original use was probably for replenished use, and that single-shot use is much more common these days, I don't think you're going to see much of a difference between the two especially if you adjust the developing time between the two. DK-50 is commonly described as having nearly straight-line gradation in the mid-tones and high-lights for studio shots.
 

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Hi MHV

I've never used the 48M developer but for more than a year I did deep tank work with DK50. People who do not mellow / season the developer often complain about runaway contrast ... seasoned it was a different beast, nice smooth midtowns nice contrast and sharpness. I'm not sure if that is much help for you as you try to decipher the differences. And oftentimes the PhotoLabIndex referred to negatives from DK50 being "crisp" ... ( it was used as a developer for portrait photographers from what I remember and I used it before and after I did lab work for someone trained in the 20s/30s as a portrait photographer ...)

Not much help but just in case you wanted to know real world experiences and not theoretical. ...
Have fun!
John
 

Rudeofus

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Higher levels of Metol and HQ also lower pH, so the increase in activity may be less than expected.
 

Murray Kelly

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For an even closer similarity compare DK-50a and FX-37 which are both from Crawley.
You do have to allow a ratio of 10:1 metolhenidone, which is generally accepted.
 
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Michel Hardy-Vallée

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Yes, 48M is recommended for full strength use and can be replenished in deep tank.

Thinking this over last night, I was wondering: if these two are pretty much the same, would the differences make sense instead from an intellectual property or business point of view? The slight differences allowed Kodak to trademark DK-50?

 
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Michel Hardy-Vallée

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I've been tempted to do that, but so far the only info I got on replenishment procedure came from Photo Formulary, and they recommend throwing away a replenished tank after one month after first mixing or 25 rolls of film.

My ideal procedure for replenishment would be like the "infinity whiskey bottle": use it whenever needed, top it off when it needs more volume or to maintain activity after a set number of rolls, since I don't shoot 25 rolls per month!

I've been using DK-50 1+1 with pretty "crisp" results as well. I mix one litre of working solution, develop up to ten rolls with it, and then discard, and start again.

 

BradS

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Michel Hardy-Vallée said:
...these two are pretty much the same, would the differences make sense instead from an intellectual property or business point of view? The slight differences allowed Kodak to trademark DK-50?
Click to expand...

This was my initial thought too. The amounts of Sodium sulfite and Sodium metaborate are almost the same and I suspect that this pair act to buffer the pH to some degree - so it would not surprise me to find no significant difference in the the PH of these solutions. The amounts of metol are similar enough that I would not expect the difference in amount to have any noteworthy effect either. However, the difference in the amounts of Hydroquinone makes me stop well short of dismissing these two as an attempt by one manufacturer to thinly disguise a competing product in order to avoid IP entanglements. The activity of Hydroquinone is known to be relatively temperature sensitive and this adds to the uncertainty.
 
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voceumana

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DK-50 was trademarked until 2016 when it was cancelled; when it was active, no other manufacturer could call their formula DK-50, but since it was a published formula, others could copy it (unless it was patented, which I doubt it was).
 
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Michel Hardy-Vallée

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I mixed a batch of 48M (was waiting for more sodium sulfite), and measured the pH and gravity of each solution.

Both are pretty close, at ph=10 and SG=1.035 for DK-50 and 1.040 for 48M, so I will test them to see if the MQ ratio makes any difference.
 
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Michel Hardy-Vallée

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I tried 48M stock (as recommended) on 400TX in 120, 5 mins at 20C, and the negatives are dense. Decent gradations, but quite dense.

This might be comparable to stock DK-50. Gives you great looking contacts, but hard to enlarge.

I'm going to try it again at 1+1, 5mins, on another roll.
 

BradS

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At what EI did you rate the 400TX ?
 
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Michel Hardy-Vallée

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BradS said:
At what EI did you rate the 400TX ?
Click to expand...

I rated the 400TX at 200, to ensure shadow details. This is what I normally do when processing in DK-50.

I have just finished processing a roll of HP5+ in 48M, but diluted 1+1. I processed for 5:45, because that is the time at which I process HP5+ in DK-50 1+1.

The 48M seems to be a bit more active than the DK-50. The HP5+ is looking good, but could use a 20% reduction in processing time to be spot on.
 
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