Progress on XTOL-concentrate

john_s · Nov 10, 2012

Alan Johnson said:
I belive the sodium metaborate that Silverprint sell in the UK is the 8-mol aka Kodalk.This has more water in it and should be less prone to crystallisation than the 4-mol from the Formulary.
There is so much ascorbate in the concentrate it may still be resistant to aerial oxidation.

The hydration of sodium metaborate is confusing. Here is a bit of information that I copied from the long-lamented Ryuji Suzuki website in relation to this nomenclature. I hope it is helpful.

<start quote>

Hydration of sodium metaborate, NaBO2, and that of Kodalk

Kodalk or "Kodak balanced alkali" is Eastman Kodak Company's trade name for sodium metaborate. The largest supplier and research institution for this compound is U.S. Borax Research Corp. in Anaheim, California. In Ullmann's Encyclopedia of Industrial Chemistry, Robert A. Smith of U.S. Borax explains industrial production processes for this compound among other boron compounds in detail.

In old literature, sodium metaborate tetrahydrate (CAS 10555-76-7) is denoted Na2B2O4 - 8H2O. This lead to old nomenclature describing hydration of sodium metaborate to be octahydrate. However, as more modern techniques became available, the actual structure of sodium metaborate is known to be better described by NaB(OH)4 - 2H2O, and this substance became to be commonly denoted by NaBO2 - 4H2O, hence tetrahydrate. According to detailed catalogues of several laboratories chemical suppliers, there is no NaBO2 - 8H2O commonly traded today. Robert Smith of U.S. Borax explains that "sodium metaborate tetrahydrate is the stable solid phase in contact with its saturated solution between 11.5 and 53.6°C." Therefore, octahydrate in old nomenclature and tetrahydrate in modern nomenclature indicate the identical chemical in the same hydration form. It is just that the nominal formula weight for tetrahydrate is half that of octahydrate. One mole of tetrahydrate would provide one mole of B(OH)4- in aqueous solution, while octahydrate would provide two moles.

The formula weight for this sodium metaborate tetrahydrate is 137.8. Common procedures for making sodium metaborate from borax and sodium hydroxide are often based on incorrect assumption that Kodalk is actually NaBO2 - 8H2O, and they have to be corrected. Fortunatelly, the proportion of mixture is correct, and the error is in final dilution, so solutions made from incorrect instruction can still be used, but by increased amount.

In order to make 1.0g sodium metaborate tetrahydrate, mix 0.692g borax and 0.145g sodium hydroxide. When dissolved in water, these two make solutions of identical composition.

<end quote>

albada · Nov 10, 2012

Thanks for the postings about sodium metaborate. I was unaware of the history of the "4-mol" and "8-mol" notations; I only knew they are confusing. In the concentrate, I wonder if the degree of hydration makes any difference. That is, I suspect the water is driven out by heat, and if so, the initial hydration makes no difference (except when weighing the powder). It would be easy to experimentally determine if the water is driven out -- maybe I'll do that.

Also, my long posting gives the impression that there's almost no flexibility of quantities of chemicals. That isn't so. If you're willing to decrease the concentration-ratio (i.e., use more PG in relation to the powders), then solubilities are less of an issue, giving you a wider range of feasible quantities.

Today, I ran a test-strip using the D316 concentrate:

pH is 8.08.
13:45 minutes (at 20C) with TMY-2.
Density-curve is very close to XTOL.
Grain and sharpness both match XTOL when compared with my loupes.

The specific gravity of my batch of D316 is 1.146. If you have a scale, measure out 23 grams/L because weighing is more accurate than measuring small volumes with a graduate.

I've found that in D316's formula, you can change the sodium metaborate (4 mol) from 2.0 g/L up to 2.7 g/L, and all will give you excellent developers (mixed directly into water; no concentrate). I was hoping to hit a pH near XTOL's 8.20, because the dev-times of various films would probably be closer to some constant (about 1.9) multiplied by XTOL's time. D316's pH of 8.08 means that constant may vary more from film to film. That's a minor problem. Anyway, I'll try raising pH by boosting the sodium sulfite some and see how that turns out.

Mark Overton

albada · Nov 15, 2012

Those of you who run test-strips may find this holder useful. Anyone can make it, and it closely mimics the environment of a roll of film. In particular, it eliminates the problem of developer-currents causing uneven (or extra) development in the strips.

Using a hacksaw, I cut a PVC pipe fitting in half, and cut two interior slots in which the strip slides.

When in the tank, the emulsion faces down, so there's a narrow space between emulsion and tank-bottom, similar to the small gap between layers on a reel. As a result, the strip develops similarly to a roll. The crosspiece that's epoxied to the top prevents this strip-holder from turning upside-down during agitation.

I exposed a 21-step Stouffer wedge twice, first with low exposure to show the toe, and again with high exposure to show the shoulder. The bump at X=3.0 is where the two graphs were stitched together.
You might have noticed in the first photo that there are two frames on the strip. On the roll, I made low/high exposures in alternation, so each test-strip has both, showing everything the developer is doing, from toe to shoulder.

This device is an improvement over the baffles I've been using. Comments, questions or suggestions?

Mark Overton

EDIT: I'm using a one-reel tank. It's so short that, with the crosspiece, there's not enough vertical space for the PVC strip-holder to turn upside-down, so agitation by inversion works well.

Photo Engineer · Nov 15, 2012

Very nice Mark.

PE

albada · Nov 17, 2012

Photo Engineer said:
Very nice Mark.
PE

Ron, thanks for the encouragement. I missed Gainer and crowd by a few years, making me sometimes feel like the party is over.

Well, here's a device I made to accurately measure strips of film, and cut them on frame-boundaries. You can use it to measure any length, including individual frames, but I'm using it to measure two-frame strips for the PVC strip-holder I posted a couple days ago.

When shooting the roll, first mark the frame-boundary on the leader with a felt-tip marker. When rewinding, leave the leader out, and cut it on the marked frame-boundary. With the lights on, load it into the home-made frame-advancer thusly:

Position the film-edge to where the scissors will be. Load it such that the crank will be pointing down when the film is at the cut-position (as shown). Turn the darkroom-lights off (or put it into a changing-bag), and make the cuts. Because there's no drift in position, every cut will be between frames. I prefer to keep the crank in the rear, as it's out of the way when I'm handling scissors with the other hand, like this:

A couple more shots to show the construction:

When selecting a junk camera from which to extract a sprocket, make sure the sprocket has eight teeth, so that one revolution will be one frame. Most have eight, but a few don't. When drilling the holes, I positioned the sprocket slightly too low, so the film jammed on entry. Sanding the top of the block down a little fixed that. The slots on top of the wooden block were cut with a saw, but it took two adjacent cuts to make each slot wide enough.

It took me an evening to make this device, but I think it was time well-spent.

Mark Overton

Photo Engineer · Nov 17, 2012

Again Mark, very neat and useful work.

Thanks.

PE

semi-ambivalent · Nov 17, 2012

albada said:
Comments, questions or suggestions?

Mark Overton

Mark,

As someone with an intimate knowledge of the miracle that is the drywall screw, and 400 feet of Eastman 5222 in the freezer, I intend to slavishly copy your film winder/counter in some fashion.

Thanks!
s-a

albada · Nov 18, 2012

semi-ambivalent said:
Mark,
As someone with an intimate knowledge of the miracle that is the drywall screw, and 400 feet of Eastman 5222 in the freezer, I intend to slavishly copy your film winder/counter in some fashion. Thanks! s-a

I hope you find this idea useful. I guess if your bulk roll won't fit in a standard bulk-loader, then you'll need something like this. But if you do copy it, I suggest cutting out the top-middle section in a Vee-shape which I drew below:

The purpose of this suggested cut is to prevent the wood from touching the film in the image-area, so it won't put scratches in your pictures.

Mark Overton

albada · Nov 18, 2012

D316 concentrate is behaving exceptionally well in tests. Here's how its density-curve compares with XTOL for TMY-2. D316 was 12 minutes; XTOL was 6.5 min:

The match is outstanding, except that D316's shoulder is a hair better (i.e., higher). Here are full-resolution crops of scans:

XTOL:

D316:

The scanner was manually focussed on the centre wedge. D316's grain is a hair finer than XTOL, which we've seen before with this type of developer, and JPEG file-size is 3% smaller, which objectively agrees that it's slightly less grainy. In loupes, grain looks the same to me. So does sharpness.

So D316 is matching (or slightly exceeding) the image-quality of XTOL.

I've also been making concentrates at various temperatures, and made the annoying discovery that propylene glycol evaporates as visible steam as low as 65C. When mixing, turn on the fume-hood over the stove, and don't worry about the constant steam.

The concentrate can be mixed at 65C, but it takes over 45 minutes to dissolve everything. At 90C, you start risking crystallization after the ascorbic acid and Phenidone are added. The constant steam-loss of PG encourages us to keep hot-time to a minimum. I suggest the following procedure (multiply this 1-litre formula by at least 2):

1. Heat 16 ml of propylene glycol to 85C.
2. Add 2.2 g of sodium metaborate 4-mol. I saw a puff of steam.
3. Stir until dissolved (a couple of minutes), keeping at 85C.
4. Add 4.5 g of ascorbic acid. Temperature will drop to about 75C. Keep between 75C and 80C.
5. When ascorbic acid is mostly dissolved, add 0.05 g of Phenidone.
6. Still until all is dissolved (around 10 minutes at 75C-80C).

I'm running more tests, but so far it's looking good.

Mark Overton

kb3lms · Nov 18, 2012

Wait a minute?

Mark,

I lost track of this thread for a bit. You were writing about the "XTOL concentrate" before and are now testing "D316"? Are they one in the same?

BTW, your inventions look pretty good! You can also get 35mm sprockets from disposable cameras.

-- Jason

albada · Nov 18, 2012

kb3lms said:
Mark,
I lost track of this thread for a bit. You were writing about the "XTOL concentrate" before and are now testing "D316"? Are they one in the same?
BTW, your inventions look pretty good! You can also get 35mm sprockets from disposable cameras.
-- Jason

Jason, thanks for the note. I hadn't thought of disposable cameras. I got my sprocket from a 1950's Edixa rangefinder. Agfa Silettes and Argus C3 bricks also contain such solid-shaft sprockets. But disposable cameras are far more plentiful.
D316 is one of the early concentrates I created back in January, and Alan Johnson mixed it and has been giving it a longevity-test. Out of all the work I've done since then, it's still the winner.

Mark Overton

kb3lms · Nov 19, 2012

Gotcha, Mark on the D316. I have the formula for D316 now, just lost track of where the conversation had gone. Although I have all the raw materials to make up some D316, I stii haven't gotten it done and my last half-quart of XTOL still sits on the shelf slowly yellowing -it looks like you-know-what now - and I can't find the films I need to process.......

But in the meantime you've done all this great work that we all benefit from. Your tests are very impressive. Thanks!

P.S. and I defintiely agree with you about missing the party! I was a member here but didn't check in for a few years. IDK why, though.

Alan Johnson · Nov 19, 2012

My tests are not as accurate as those done by Mark,but I found that APX100 gives a similar result in D316 to that obtained with Xtol.
Whilst Ryuji cautioned that DS-10 was not satisfactory for some films including APX100,my initial test result is that D-316 is OK.
http://web.archive.org/web/20090603...loper_Recommendations#Caution_for_DS-10_users

john_s · Nov 19, 2012

I'm thinking of trying D316. I have two questions.

1. If I use a bit more propylene glycol, say to make 25mL of concentrate instead of 20mL, will that make it easier to dissolve and less likely to crystallize, or will the different concentration of metaborate alter the solubility of the ascorbic acid? I would obviously use 25mL of the concentrate to make 1_L of working solution.

2. Whichever version of sodium metaborate I have, it shouldn't make any difference, should it? In my post above where I pasted Ryuji's comments about the naming of sodium metaborate (tetrahydrate and octohydrate) although the theoretical compositions of the two compounds give very different molecular weights (one double the other) it seems to me that 2.2 grams of either is exactly the same when dissolved. I have bought chemicals from a supplier who has been generally a bit slack with noting water of crystallization, which usually makes a difference but not, I think, in this case. It's been a while since I did high school chemistry (1965).

albada · Nov 20, 2012

john_s said:
I'm thinking of trying D316. I have two questions.

1. If I use a bit more propylene glycol, say to make 25mL of concentrate instead of 20mL, will that make it easier to dissolve and less likely to crystallize, or will the different concentration of metaborate alter the solubility of the ascorbic acid? I would obviously use 25mL of the concentrate to make 1_L of working solution.

Good to hear that!

I think that boosting the propylene glycol (PG) will make it easier to dissolve the powders. But at the temperatures I gave, everything dissolved in a reasonable time, and comfortably below the crystallization-point. Boosting PG will have a small effect on the developer, as it reduces pH a tad. But I doubt the difference would be significant.

john_s said:
2. Whichever version of sodium metaborate I have, it shouldn't make any difference, should it? In my post above where I pasted Ryuji's comments about the naming of sodium metaborate (tetrahydrate and octohydrate) although the theoretical compositions of the two compounds give very different molecular weights (one double the other) it seems to me that 2.2 grams of either is exactly the same when dissolved. I have bought chemicals from a supplier who has been generally a bit slack with noting water of crystallization, which usually makes a difference but not, I think, in this case. It's been a while since I did high school chemistry (1965).

Actually, the kind of metaborate will make a substantial difference, because the number of moles of the anhydrous form (i.e., NaBO2) in 2.2 grams will differ. For 8-mol metaborate, you'll need 3.0 grams. If you have a pH meter, you can mix the ingredients directly into water (including the PG) and see if the pH is around 8.08.

Without a pH meter, you could mix the concentrate using 2.2 grams, and see how long the ascorbic acid takes to dissolve at 75C (assuming 20 ml of PG). If it takes longer than 5 minutes to dissolve most of it, then you probably have the 8-mol s.metaborate, and will need to add another .8 grams of it. Alternatively, you could mix the concentrate using 20 ml of PG and 3.0 grams of metaborate, but at a temperature of 85C for everything. If it crystallizes (white marks on bottom of beaker and then cloudiness), then you know you should start over with 2.2 grams.

Good luck,

Mark Overton

john_s · Nov 20, 2012

albada said:
.......
Actually, the kind of metaborate will make a substantial difference, because the number of moles of the anhydrous form (i.e., NaBO2) in 2.2 grams will differ. For 8-mol metaborate, you'll need 3.0 grams. If you have a pH meter, you can mix the ingredients directly into water (including the PG) and see if the pH is around 8.08.

Without a pH meter, you could mix the concentrate using 2.2 grams, and see how long the ascorbic acid takes to dissolve at 75C (assuming 20 ml of PG). If it takes longer than 5 minutes to dissolve most of it, then you probably have the 8-mol s.metaborate, and will need to add another .8 grams of it. Alternatively, you could mix the concentrate using 20 ml of PG and 3.0 grams of metaborate, but at a temperature of 85C for everything. If it crystallizes (white marks on bottom of beaker and then cloudiness), then you know you should start over with 2.2 grams.

Good luck,

Mark Overton

Thanks Mark. About metaborate:

tetrahydrate NaBO2-4H2O
octohydrate Na2B2O4-8H2O

The octohydrate has twice the molecular weight of the tetrahydrate. So 2.2g of it would have half the number of moles. But each mole of it is equivalent to two moles of the tetrahydrate. When dissolved, wouldn't it be the same?

(The situation seems quite different to something like, say, sodium carbonate, where the one mole of Na2CO3 can have zero, one, seven or ten molecules of water. Obviously then the water of crystallization has to be taken into account when weighing out.)

Rudeofus · Nov 20, 2012

john_s said:
Thanks Mark. About metaborate:

tetrahydrate NaBO2-4H2O
octohydrate Na2B2O4-8H2O

You might have misread something here. There are four compounds appearing in literature:

NaBO2 * 2 H2O
NaBO2 * 4 H2O
Na2B2O4 * 4 H2O
Na2B2O4 * 8 H2O

Note that compounds 1 and 3 are effectively the same thing, and the same applies to compounds 2 and 4. Both compounds 2 and 3 could justifiably be called tetrahydrate but are certainly not the same, and that's where the confusion comes from. Mark has written about this and linked to relevant information. Make sure you know which compound you have and use the amount recommended by Mark for that amount. You dev is likely going to develop film even if you pick the wrong amount, but if you want to get the same good results that Mark achieved with his formula, you better get the metaborate amount right.

Alan Johnson · Nov 20, 2012

See also Rudi's post #71.
You need to find out if you have:
(1) Sodium metaborate 4-mol in which case use the amount specified by Mark, or:
(2) Sodium metaborate 8-mol (this is also known as Kodalk)in which case multiply the amount specified by Mark by 1.354, eg 2.2gx1.354=3g
The quote from Ryuji is about 2 crystalline forms of the same substance,you are correct to say they are the same when dissolved, in this context it is only of academic interest.

john_s · Nov 20, 2012

Thank you Rudeofus and Alan. The supplier of my sodium metaborate (Vanbar in Melbourne) who package bulk chemicals have called it Kodalk so it should be the 4-mol. I will try to accurately measure the solubility which might determine which version I have.

Alan Johnson · Nov 20, 2012

No, see post #74, it is thought Kodalk is the 8-mol.

8-mol is NaBO2.4H20 which used to be written Na2B2O4.8H2O and called sodium metaborate octahydrate.This agrees with The Darkroom Cookbook p177 which gives the composition of Kodalk as sodium metaborate octahydrate, ie they use the old name.

If you have Kodalk the weight of metaborate given by Mark has to be multiplied by 1.354. as he uses the 4-mol compound.

albada · Nov 20, 2012

richydicky said:
Thanks for the great work. I have wanted to try XTOL but it would be a waste making 5 litres. I am planning to buy the chemicals tomorrow to make a batch to your formula but I have just checked the supplier list and what they have is 8-mol sodium metaborate. Would appreciate the correction needed for the amount, my chemistry knowledge is over 30 years old!

richydicky: I owe you an apology! I noticed your question months later when this topic of 4-mol/8-mol came up again, and saw that I had not answered it. I must have overlooked it, being distracted or in a hurry. Sorry about that.

Here's a link to the earlier discussion about this topic which Alan has referred to:
(there was a url link here which no longer exists)

I'll update the formula to specify 2.2g of 4-mol, or 3.0g of 8-mol sodium metaborate.

Mark Overton

Photo Engineer · Nov 20, 2012

The question of 4 mol vs 8 mole keeps coming up! The differences are in buffer capacity and pH, both of which are different for these two compounds when used at equal weight. The pH difference is tiny, but meaningful and the buffer capacity is also small. The former is changes contrast, speed and / or development times while the latter has a tiny effect on sharpness and upper shoulder.

PE

Rudeofus · Nov 21, 2012

Photo Engineer said:
The question of 4 mol vs 8 mole keeps coming up!

Which doesn't surprise me in the least. Given that the metaborate ion is generally described as BO2-, one would assume that the general nomenclature would distinguish between 2 mol and 4 mol. With the historical context in mind it makes sort of sense to have 4 mol and 8 mol, but people entering the field are likely confused. If I were to formulate a recipe today, I'd either start with Borax and NaOH/Na2CO3, or state the exact compound in my recipe NaBO2 * 2 H2O (or NaBO2 * 4 H2O), and maybe state that the compound is sold as Sodium Metaborate 4 (or 8) mol.

john_s · Nov 21, 2012

It's confusing. Even the manufacturer gets confused. If you go to the two links in post #71 and open the links to Product Data Sheet you will find that on page two of each (top right hand column) that the same molecular formula is given for both compounds. One of them is wrong, of course.

I'm thinking of trying to ascertain which of the metaborates I have. I note that their solubilities in water differ, so I'll try to dissolve the one that's most soluble at 20degC and if it doesn't all dissolve I'll add water to see if its solubility matches that of the other one.

But tell me, I'm used to solubilities expressed as g/L of solution (or 100mL of solution). The product data sheets show solubilities as "percent by weight." So does this mean that x grams dissolves in 100mL of water to make an amount of solution that's probably not 100mL?

Rudeofus · Nov 21, 2012

Determining the solubility of a compound can be a time demanding procedure, I'm not sure you're ready for this. Try dissolving 359 g/l Sodium Chloride if you don't believe me :munch:

If you get the stuff from a reputable source, they should be able to tell you exactly what they have, possibly even a CAS number which would completely eliminate any ambiguity. It's their business after all. The biggest problems come from published formulas which carelessly state "Sodium Metaborate" instead of the exact compound to be used, and no solubility test is going to help you with these.

Progress on XTOL-concentrate

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