Measuring tiny quantities of Phenidone and Potassium Bromide

After I got a bunch of help from the knowledgeable folks on this forum and managed to successfully switch over to E72 paper developer, I got curious about other DIY options, and found a Mytol recipe I want to try. By all accounts it produces nearly identical results to XTOL film developer, it just has a terrible shelf life.

I'm pretty dedicated to mixing up small, one-shot batches of my developers (I'm even doing this with E72 because it's inexpensive enough), which is why I've never tried XTOL before. Pretty strictly an HC-110 and Rodinal guy to this point. I want to try this approach with Mytol. For me, a single-roll batch of Mytol is 200ml total soup at 1+1 working strength (so 100ml of stock solution).

That means two of the ingredients would need to be measured in quantities to tiny that I don't trust my reloading scale's precision. Specifically, this quantity of developer would require 15mg of Phenidone and 10mg of KBr. For paper developer I can fudge it a bit, since I'm doing test strips and seeing immediate results in the tray, so if one batch of E72 has a bit more Phenidone in it than a different one, I probably won't even notice, just compensate as I go.

The obvious solution would be to mix up some kind of solution that uses a small-but-measurable quantity of Phenidone at a known dilution, and then use a more easily measurable quantity of that solution to make the working-strength Mytol. It looks like people regularly do this with Phenidone and ethanol. Would this work in another fluid? Isopropyl alcohol? Denatured? Water? Propylene Glycol? Once Phenidone is in solution, does a timer start ticking on shelf life?

Same questions for KBr, really. I'm not a chemist. Thanks in advance!

This video may be useful:

Very informative video, thank you. Biggest takeaway for me is that it seems like my powdered Phenidone has a shelf life of something like 6 months, even in an airtight container? That's important information to know. Seems like I might be best served by mixing up all of it into a weak solution with Propylene Glycol, which should extend its life to something like years, as well as making it much easier to measure with precision.

Does anyone know if there is a similar solvent that would allow me to make a weak solution of KBr without spoiling the shelf life? By my rudimentary understanding, KBr won't dissolve in Propylene Glycol as it's an inorganic salt. Would I be safe therefore to just mix it up in distilled water to make it easier to measure, and could I expect it to last more or less indefinitely as an aqueous solution?

One last question: If I were to make a 1% solution of Phenidone in Propylene Gycol and a 1% solution of KBr in distilled water, I'd need 1.5ml of Phenidone solution and 1ml of KBr solution to make 200ml of working strength Mytol (as well as other powdered ingredients). Could I safely combine these two solutions into a single 2.5ml airtight glass container for long-term storage, or would that once again destroy the shelf life of one or the other agent?

Phenidone dissolves well in warm Propylene Glycol. I have prepared 1% and 5% stock solutions and they haven't changed over many years now.

When it comes to Bromide, you can mix an 1% stock solution in water and be done with it. It will last forever. I do wonder, which Mytol formula you use, though. I have seen a credible report about three versions of Mytol, neither of which lists bromide ...

PS: my stash of powdered Phenidone is many years old and just keeps going. Don't worry too much about its shelf life.

I got my recipe for Mytol from this old Filmwasters post from 2016:


It's a tiny quantity, but it makes sense as an ingredient to my limited understanding. AFAIK none of the other ingredients act as a restrainer.

Instant mytol works pretty well. It's equivalent to Xtol 1+1.

I second the idea of making solutions. The main thing is to make them easy to measure. 5% is a good number for KBr. I made a 4% solution of phenidone in propylene glycol a couple of years ago, and it's still fine, but it's a little too strong. 2% would be easier to measure

So did I incorrectly assume that the Instant Mytol recipe would match XTOL stock? I was assuming I’d need to dilute 1+1 to match XTOL 1+1. Should I expect to double my non-water ingredients for 200ml of working strength dev that matches XTOL 1+1?

Rudeofus said:

Phenidone dissolves well in warm Propylene Glycol. I have prepared 1% and 5% stock solutions and they haven't changed over many years now.

When it comes to Bromide, you can mix an 1% stock solution in water and be done with it. It will last forever. I do wonder, which Mytol formula you use, though. I have seen a credible report about three versions of Mytol, neither of which lists bromide ...

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Like @Rudeofus, my record of the Instant Mytol recipe has no Potassium Bromide. Somebody might have added that restrainer to reduce fog in old film, and then propagated the formula.

I worked on some XTOL-clone recipes around 10 years ago, and my notes say the one below delivers at least XTOL-quality, and perhaps a bit better. Here is its one-liter formula:


Add 30% to XTOL's development-time.
If you want to tinker with XTOL-like developers, either this or Instant Mytol (with no p.bromide) is a good place to start.

Mark

@Rudeofus has indeed given the crucial answers. A solution of phenidone in glycol (I prefer propylene as it's non-toxic) will last a long time; I've never had mine go bad. 1% is convenient for Mytol-purposes in my experience. Powdered phenidone remains viable for a long time; I don't know where the stories come from that it would expire in a matter of a few years, let alone shorter.

I suppose many of us have our Mytol recipes; here's the one I always use; makes 1 liter:

Borax	1.4​
Sodium sulfite	60​
Ascorbic acid	11.5​
Sodium carbonate monohydrate	5.64​
Phenidone	0.15​

Adjust pH to 8.20 by adding drops of a NaOH (pH up) or acetic acid (down) solution. Frankly, I don't bother anymore these days and just use it as is under the assumption that my methods and materials should consistently yield the same outcome, even if that happens to be slightly 'off' from the official standard.

In my experience, the formula above is a bit faster than official XTOL (stock; undiluted); which is to say that at least in some films (esp. Fomapan 100), I get a higher gamma than I'd expect given the XTOL development parameters. Then again, I ran a roll of Delta 100 yesterday and this looks pretty normal to me, so the performance should be "in the ballpark" alright. For me, some deviation from official XTOL performance is inconsequential, but if it's important to you, make sure to benchmark your XTOL clone (whichever one you end up using) with genuine XTOL and then adjust development recipes accordingly.

The rationale behind the formula I posted is to replace the metaborate (which I didn't happen to have) with the same stuff made in situ from borax and sodium carbonate. It also replaces the ascorbate called for in most recipes with ascorbic acid - again a matter of what I did vs. didn't have tucked away in a closet somewhere. This explains the difference in buffering/activator ingredients and ascorbic acid content between the formula posted above by @momus and mine.

I once worked out the chemistry and conversion math to get to the formula above, but sadly didn't save my notes, so I'd have to reconstruct them. If you feel like it, it would be a nice exercise so you could then point out the possible errors in my approach

As a chemist I often have to make up standards of accurate concentration in the low parts per million range. It's not difficult as long as you do it multiple steps (serial dilution).
Presumably your balance/scales won't be as accurate as the one I use (ours are normally used to 0.1mg precision, but can be switched to 0.01mg) but you can still make up a concentrate, then (after its all dissolved & mixed) transfer a known small volume (by pipette or syringe) & dilute. On occasion this dilution stage is repeated several times.

I doubt your formula will need the ingredients made up as precisely as the standards I make up, so a syringe & a measuring cylinder should be good enough for your dilutions. Diluting by weight rather than volume does also work, but I think volume is easier & probably more accurate with cheap scales.

All of the above is good advice. You might also take a look at my PC-512 Borax developer, where the alkali and developing agents are mixed just before use, from a concentrate and a borax stock solution. Keeping properties are really good (well over a year, probably more, but I used it up). It only has 4 ingredients: Propylene glycol, phenidone, ascorbic acid, and borax. None of these need anything but scale accuracy to a tenth of a gram. Development times are nearly the same as XTOL, tonality is pretty similar. There are a bunch of samples on my Flickr stream if you are interested.

relistan said:

Development times are nearly the same as XTOL, tonality is pretty similar.

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But it gives a bit more grain, doesn't it? Not that this is a problem per se, but for me, one of the reasons for using an XTOL-derivative is its grain rendition especially on higher speed films.

koraks said:

But it gives a bit more grain, doesn't it? Not that this is a problem per se, but for me, one of the reasons for using an XTOL-derivative is its grain rendition especially on higher speed films.

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Yes, it's not a replacement for XTOL if you want a solvent developer. I wasn't trying to imply that it is, only that it's simple to make and has a lot of what @BHuij was looking for. Since they like Rodinal and HC-110 it seems inline with those expectations. Still, the Ilford films in particular seem to exhibit pretty good grain behavior in PC-512 Borax. Here's Kentmere 400:

Indeed, that looks perfectly fine to me. If I get back in the mood of experimenting with different developers one of these days (it comes and goes), I'll be sure to try your PC512Bx!

koraks said:

@Rudeofus has indeed given the crucial answers. A solution of phenidone in glycol (I prefer propylene as it's non-toxic) will last a long time; I've never had mine go bad. 1% is convenient for Mytol-purposes in my experience. Powdered phenidone remains viable for a long time; I don't know where the stories come from that it would expire in a matter of a few years, let alone shorter.

I suppose many of us have our Mytol recipes; here's the one I always use; makes 1 liter:

Borax	1.4​
Sodium sulfite	60​
Ascorbic acid	11.5​
Sodium carbonate monohydrate	5.64​
Phenidone	0.15​

Adjust pH to 8.20 by adding drops of a NaOH (pH up) or acetic acid (down) solution. Frankly, I don't bother anymore these days and just use it as is under the assumption that my methods and materials should consistently yield the same outcome, even if that happens to be slightly 'off' from the official standard.

In my experience, the formula above is a bit faster than official XTOL (stock; undiluted); which is to say that at least in some films (esp. Fomapan 100), I get a higher gamma than I'd expect given the XTOL development parameters. Then again, I ran a roll of Delta 100 yesterday and this looks pretty normal to me, so the performance should be "in the ballpark" alright. For me, some deviation from official XTOL performance is inconsequential, but if it's important to you, make sure to benchmark your XTOL clone (whichever one you end up using) with genuine XTOL and then adjust development recipes accordingly.

The rationale behind the formula I posted is to replace the metaborate (which I didn't happen to have) with the same stuff made in situ from borax and sodium carbonate. It also replaces the ascorbate called for in most recipes with ascorbic acid - again a matter of what I did vs. didn't have tucked away in a closet somewhere. This explains the difference in buffering/activator ingredients and ascorbic acid content between the formula posted above by @momus and mine.

I once worked out the chemistry and conversion math to get to the formula above, but sadly didn't save my notes, so I'd have to reconstruct them. If you feel like it, it would be a nice exercise so you could then point out the possible errors in my approach

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Fantastic, I'll omit the KBr then, sounds like it's not needed since I'm not using expired or otherwise fogged film. I'm inclined to do the same as you, mix up in distilled water and not worry overly much about pH. I'm going to be calibrating times for zone system use anyway, so as long as it's consistent from batch to batch, that's what's important. I don't need it to give perfect results on the first try with published XTOL times.

If I'm understanding correctly, your recipe makes a stock solution that should be more or less equivalent to XTOL stock. That means I'd want to halve the recipe in the same amount of water to get 1:1 working strength, correct? I won't be benchmarking against XTOL or anything. I just decided I wanted to try experimenting with a fine-grain developer. XTOL was always one that seemed interesting to me, but I never wanted to mix up 5 liters of it.

I'm with you on not having metaborate or ascorbate on hand, and not a ton of interest in trying to synthesize any to keep on hand. Getting the right amount of reactants/reagents to make them as I mix up seems like the right approach, given how easy it is to source borax, vitamin C, and washing soda. I already have two of the three for E72.

If the developer is working for you and it's producing results that are comparable to XTOL, then I don't think I'll worry too much about doing a bunch of stoichiometry to verify your math. It's been 15 some-odd years since high school chemistry, and I never did any in college, so I'd have to do a lot of Googling to even remember how

There are basically two reasons I want to try this stuff, advantages that XTOL is supposed to have over HC-110. First is fine grain. HC-110 isn't bad with slower films like FP4+ and Delta 100, but I recently shot some CMS 20 II to compare it to Delta and made a video about it. One of the comments on the video suggested that XTOL could yield significantly more resolution from Delta 100 than HC-110 and I was curious enough to try it out. The other is film speed. I use rotary processing for consistency and economy of chemicals. It seems the constant agitation tends to reach proper contrast before shadows have time to develop out as much as they otherwise might with a less agitated development regime. Pair that with developers that are not known for giving full film speed in the first place, and I end up shooting my FP4+ and Delta 100 at EI 64, and my HP5+ at EI 250. On overcast and cloudy days, even EI 250 is pushing the limits on what I can handhold unless I'm shooting everything at f/2. If XTOL buys me an extra 2/3 of a stop, even that could make a pretty significant difference in what I can confidently shoot without a tripod when I don't want to use one.

If you were going to do rotary processing with this Mytol recipe diluted 1+1, what would you rate your FP4+ at? Realistic to expect full film speed if I place my shadows on Zone III? Or better to do something like 80 or 100?

There are basically two reasons I want to try this stuff, advantages that XTOL is supposed to have over HC-110. First is fine grain.

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If you are trying for less apparent grain, I suggest you not dilute your MyTOL/XTOL and just use it stock. Why do you want to dilute it? Economy? Constant agitation will also increase grain.

The other is film speed.

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HC-110 will reach full film speed with those films so if you are getting less than full film speed I would suggest it's more likely down to processing than to developer choice. One possibility: more dilute versions of any developer containing solvent will have a lessened solvent effect and has the potential to lower film speed. Sulfite or its equivalent (HC-110 has a complicated solvent mix) will expose centers for development that are not available to a non-solvent developer. That can give you more film speed for the same exposure. Diluting your developer gets you more perceived sharpness in some cases, but can also give you less film speed when compared to a more solvent (less diluted) dilution.

Excellent info. I did a lot of reading about XTOL when trying to decide on a dilution. Seems like stock gives the finest grain but also the lowest perceived sharpness. As you dilute further, both grain and apparent sharpness increase. Many people seemed to think that 1+1 dilution from stock was the sweet spot in getting an increase in apparent sharpness over stock without getting a significant increase in grain.

But if higher dilutions also equate to slower speeds, then I should probably try both stock and 1:1 to see what I like better and what kind of speed I can get out of it.

And at the end of the day, it's possible I should just plan on not using rotary processing for this developer. I started using it because it was the best way to get really even and consistent development for sheet films in a tube. Far superior results to tray development for me. I wanted to use the same times for roll film so I didn't have to do another round of calibration for everything, so I devised a way to use my rotary base with my Nikor steel tank, and it has worked well for that. And economy of chemistry use as an added bonus - I can develop a roll of film with only 2ml of HC-110 or Rodinal syrup in many cases.

But now I'm really starting to see the disadvantage of constant agitation in that it effectively robs film speed. For much of my work that's a fine tradeoff. I don't shoot my medium format or large format cameras handheld anyway, and my subjects tend to be the kind that are good at holding still (e.g., mountains). Given how inexpensive Mytol is, and considering that I probably won't be using it for sheet films anyway, I think I will try mixing up a sufficient amount to try a more standard agitation scheme. That will probably give me finer grain and higher film speed than I can achieve with rotary agitation. Will try both stock and 1:1. Thanks!

BHuij said:

If I'm understanding correctly, your recipe makes a stock solution that should be more or less equivalent to XTOL stock. That means I'd want to halve the recipe in the same amount of water to get 1:1 working strength, correct?

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Yes, indeed.

BHuij said:

If you were going to do rotary processing with this Mytol recipe diluted 1+1, what would you rate your FP4+ at?

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It's been years since I shot any FP4+ and I've never run it through XTOL or Mytol, so I'd just rate the film at box speed, scoot over to the massive dev chart and pick the XTOL1+1 time, then take it from there! Sorry for not being more specific, but when in doubt, does as it says on the tin, I'd say

As to the possible benefits of this over HC110 - you'll have to test and compare for yourself. I've learned not to expect miracles from different developers, although the differences are often very real if you look for them. It's a reasonable avenue to research, in any case.

Yeah, I'm happy enough with my current arsenal of films and developers (which has already been thoroughly tested, calibrated, etc), that if this didn't sound like fun I wouldn't bother. But I admit I do enjoy the tinkering, sometimes as much as the photography. And I also find myself wanting to walk around with a 35mm camera and shoot handheld more frequently than I did before I had kids. Back then I could take an afternoon to schlep my Intrepid/RB67 and tripod around basically whenever I wanted. These days I frequently have to fit my photography outings into a pretty tight window of time

So if I can get anything approaching EI 125 from FP4+ and EI 400 from HP5+, and especially while maintaining reasonable grain and sharpness, that opens some doors for me on the kind of work I can do handheld.

Trying stuff is, in and of itself, fun in a lot of cases. I'm not trying to discourage tinkering!

On the subject of the difficulty of weighing tiny amounts of phenidone, this post from Sandy King, the inventor of Pyrocat-HD, suggests that precision is not as important as we might think.

I use a "digital pocket scale" 0-200g with has worked well for at least 10 years and $10-20 investment.
It has worked well for such quantities of chemicals. I make pyrocat hdc with it every year or so as well as some alt process chemicals.

For small quantities of liquid, I have disposable 3ml pipettes marked with 1,2,3 ml marks, and dayquil/nyquil/kidsmedicine cups for 0-15ml and 0-30ml which are nicely marked with black lines on clear plastic.

john_s said:

On the subject of the difficulty of weighing tiny amounts of phenidone, this post from Sandy King, the inventor of Pyrocat-HD, suggests that precision is not as important as we might think.

Dimezone-S instead of phenidone in Pyrocat-HD?

I have acquired some Dimezone-S which is reputed to be a better-keeping variety of phenidone. I'm interested in knowing if anyone has tried it, and if so any advice about equivalent quantities. Someone on the old pure-silver list suggested that I substitute equivalent molar weights (i.e...

www.photrio.com

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I have read this, and so I was comfortable measuring out the 71mg I need for one 8x10 tray full of E72 developer at 1+3 strength, just dry. I use my reloading scale set to grains, and measure out 1.1 grains. As I said before, if I'm printing I don't need much precision because I can always run another test strip to make sure I know exactly the print density I'm getting. But Mytol would need about 1/6 of that amount, well below where I trust my scales, and a mistake in measurement here could potentially cost me a roll of film with no do-overs. So even if I could get away with some slop here, it seems prudent to make the weak solution in propylene glycol and measure precisely out from there.

jp498 said:

I use a "digital pocket scale" 0-200g with has worked well for at least 10 years and $10-20 investment.
It has worked well for such quantities of chemicals. I make pyrocat hdc with it every year or so as well as some alt process chemicals.

For small quantities of liquid, I have disposable 3ml pipettes marked with 1,2,3 ml marks, and dayquil/nyquil/kidsmedicine cups for 0-15ml and 0-30ml which are nicely marked with black lines on clear plastic.

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Glad you found a $20 scale you trust. I'm perfectly fine to measure down to maybe half a grain (32mg, give or take) with my inexpensive reloading scale, but couldn't find anything in my price range that I would trust to tell me the difference between 0mg and 10mg worth of Phenidone.

Luckily I do have some good small-quantity syringes that I picked up when I first got into alt processes. I mix my gold toner one-shot for Kallitypes and wanted to be able to use the smallest possible amount of gold chloride so I wasn't wasting the precious liquid in that expensive little brown bottle haha. These syringes should be fine for measuring out Phenidone solution.

jp498 said:

I use a "digital pocket scale" 0-200g with has worked well for at least 10 years and $10-20 investment.
It has worked well for such quantities of chemicals. I make pyrocat hdc with it every year or so as well as some alt process chemicals.

For small quantities of liquid, I have disposable 3ml pipettes marked with 1,2,3 ml marks, and dayquil/nyquil/kidsmedicine cups for 0-15ml and 0-30ml which are nicely marked with black lines on clear plastic.

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+1 on the kid's medicine cups and syringes for small liquid amounts. May as well turn all those ear infections into something positive! (or negative, as the case may be)