[Leica] Long Xtol rant

[chs2018 at med.cornell.edu (Chris Saganich)]

Thanks Marty that was excellent and answered a few questions regarding my 
previous Xtol experience.  I liked xtol very much buy those 5 liter bags 
put me off.  Is it ok to split the powered contents into smaller portions 
then mix it one liter at a time??  One liter for development and one for 
replenishment?
Chris

At 08:40 AM 7/25/2007, you wrote:
>Since there is a bit of interest in chemical developers after the LuG 
>being almost completely digital, I thought I'd post this.  I wrote it for 
>a newsletter a few of us here in Adelaide write and send around to each 
>other.  A lot of this is based on discussions I've had with LuGer John 
>Black.  The formula for JB9 is entirely his - and it's elegent and 
>effective.  My own experiments in pH were initiated after discussions with 
>him and follow an approach I developed from our discussions.
>
>What follows is a long rant about Kodak Xtol.
>
>Xtol is probably the best commercially available developer for 35mm 
>film.  Why is it so good?  It is an ascorbate developer.  Ascorbates are 
>effective developers of silver– with about the same efficacy at 
>developing as hydroquinone, but the development by-products of ascorbates 
>are acidic and act as development inhibitors.  These by-products inhibit 
>development proportionally to exposure (i.e. they inhibit more in dense 
>areas of the negative and less in thinner areas).  All ascorbate 
>developers are, therefore, compensating developers with high acutance, 
>dependant to some extent on the other components of the developer.  This 
>is good for tonality.  ‘Compensation’ is claimed for many 
>developers, but the ascorbate ones are among only a few where it has any 
>real scientific basis or measureable effect.  Kodak’s chemists were 
>clever with Xtol in several ways beyond using an ascorbate as the primary 
>developing agent.  They added enough sulfite that the stock!
>   solution can be used as a grain-reducing developer and as a 
> replenishment developer where the only replenisher needed is more Xtol. 
> This sulfite concentration, combined with high activity, allows the 
> developer to be used at dilutions of up to 1+1, 1+3 or 1+5 depending on 
> the film being developed.  This results in enhanced edge effects; it 
> maximises direct development and minimises solution or physical 
> development (called ‘solvent action’), increasing 
> sharpness.  They also used dimezone-S as the superadditive 
> co-developer.  Dimezone-S is a potent developer at low concentrations (it 
> is, after all, similar to phenidone) but is easier to dissolve in water 
> than phenidone and is less likely to oxidise once in solution.  Properly 
> mixed Xtol is actually quite stable – not Rodinal or PMK Pyro stock 
> stable, but very good.
>
>So it’s sharp and has great tonality.  Super.  Unfortunately, Xtol 
>got a reputation early on for both failing catastrophically and leaving 
>odd artefacts in negatives.  So, what gives?  Is it great or does it suck?
>
>As usual, the answer to both is yes. Xtol fails for two 
>reasons.  Ascorbates are strong antioxidants and will scavenge oxygen from 
>solution.  Unfortunately the oxidation products of ascorbates do not 
>develop latent silver images and do not present a colour change in 
>solution.  This explains what we already know – Xtol can die without 
>warning. The other reason Xtol can fail is that the oxidation of 
>ascorbates is catalysed by metal ions in water – particularly 
>divalent cations (they are the 2+ ones).  These include calcium and iron, 
>the former common in ‘photo grade’ chemicals and the latter 
>common in tapwater.  Odd donut-shaped dots on negatives developed in Xtol 
>are seen sometimes even by people who are careful about air and mixing.  I 
>suspect this occurs when impure dilution water is used and a little 
>particle of iron or some other substance ends up onthe film, oxidising the 
>ascorbate (and therefore inhibiting development) forsome distance around.  
>I!
>  t’s not likely tobe in the original mix water, since impurities 
> here would probably kill the developer, unless it was mixed and then used 
> almost right away.
>
>“Sudden Xtol death syndrome” can be fixed by keeping bottles 
>completely full and in the dark; “Xtol spots” can be avoided 
>by always using distilled or deionised and filtered water to mix and 
>dilute Xtol.  Whether you think that is worth the bother is up to you.  I 
>think it is.
>
>Can you mix your own Xtol? Sort-of.  Mark Rabiner sent aroundthe basic 
>formula from the patent (that’s not an MSDS – an MSDS is the 
>“material safety data sheet” and the one for Xtol can be 
>accessed by going here: 
>http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=2879/4648&CID=go&idhbx=msds&pq-locale=en_US&_requestid=2627
> 
>and typing Xtol in the product name box) which comes from the 
>patent.  There are, however, indications from the physical behaviour of 
>Xtol that what Kodak sells is somewhat different.  Xtol stock solutions 
>have a pH of 8.2 (what Kodak says); diluted to 1+3 the pH rises to 
>8.3-8.4.  If you make the patent version, the startings olution is 
>8.35-8.4 and it stays fairly stable with dilution.  Those pH differences 
>might not seem like alot, but they’re important.  The version from 
>the patent is also about 30% less active. What does this tell 
>us?  The‘weakly alkaline’ (Kodak’s terminology) pH must 
>come from a buffe!
>  r, rather than just from metaborate and metabisulfite. I suspect a small 
> amount of boric acid (i.e. a metaborate-boric acidbuffer) – it 
> makes the most sense chemically; I also have some supporting data 
> frommass spectroscopy analysis of commercial Xtol. The EDTA is also 
> probably not enough on its own to sequester the divalent cation 
> concentrations that Xtol can handle – I did this by adding known 
> concentrations of dilute cation solutions to Xtol and self-made analogues 
> and comparing them.
>
>So, what can you really do? Buy Xtol, of course.  But if you really want 
>to make a substitute, the following are options:
>
>Patrick Gainer’s PC-TEA
>9 grams ascorbic acid
>.25 grams phenidone
>100ml triethanolamine (TEA)
>Heat the TEA in a pyrex container in themicrowave for 30 sec.-1 minute, 
>and add the ascorbic acid. When it isdissolved, add the phenidone.  Be 
>careful, because the TEA will get VERY hot.
>
>Dilute the concentrate 1:50 for use.
>
>PC-TEA is very good and if you have access to cheap TEA as those in the US 
>do through www.chemistrystore.com it costs hardly anything.  It’s 
>grainier than Xtol, however, and doesn’t change its characteristics 
>when diluted more.  It works because it is very alkaline, which I think 
>contributes to the grain characteristics of films developed in it.  Many 
>other ascorbate formulae have these flaws – the absence of the 
>weakly alkaline pH, low sulfite concentration (but withsome sulfite still 
>present) and the increase in activity with dilution are what make Xtol 
>extraordinary.
>
>John Black’s JB9 is functionally the same as Xtol, but you mix it 
>yourself.
>
>The developer is made from 3 liquid concentrates that are stable for at 
>least 6 months, perhaps a year (stability testing underway).  Store the 
>solutions in glass bottles, tightly capped. The solution A should be store 
>in the dark (a closed cabinet is fine) or in an amber bottle.
>
>Solution A:  (Phenidone, ascorbic acid)
>
>Phenidone               1.25 gm
>Ascorbicacid-           50.00 gm
>Ethyelene or
>propylene glycol
>or dry methanol-        600 ml
>
>Warm up solvent to hot tap water temp before dissolvingcomponents. They 
>will dissolve at about 100-125F. Dissolve ascorbic acid first.
>
>Solution B:  TBE (Tris-borate-EDTA) Sigma cat# T3913
>One 1L dry pkg dissolved in 1L DI water
>Other buffer concentrates may be substituted if made up to about half 
>molar at a pH of about 8.3.  Boric acid-metaborate(BA/Kodalk) would be 
>fine, you may have to fiddle a bit to get the right pH.
>
>Solution C:  Saturated Na Sulfite solution
>Na Sulfite(anhydrous)-           180 gm
>Distilled water-                 600 ml
>
>Stir vigorously for about 30 min.  Temp will rise a bit and it will almost 
>all go into solution.  Let stand overnight to equilibrate (some will 
>crystallize out).  Use after that.
>
>JB9 developer:
>SolA:                     10 ml
>SolB:                     50 ml
>Sol C:                    20 ml
>Distilled H2O             Fill to 250 ml
>
>Add sol B and C to water first, mix and then A (protects phenidonefrom 
>oxygen in water).  This is enough todevelop 1 roll of 35mm film.  Scale up 
>as necessary.  Works best as a 1 shot developer at 68F, with moderate 
>agitation.  I use 13 min for Tri-X.
>
>I’ve used the tris and metaborate/boric acid versions of JB9 and 
>they are functionally identical to Xtol. You can modify the sulfite 
>concentration as you like.  One of the best things about JB9 from my 
>perspective is that you can mix the developing agents to the same 
>concentration as Xtol stock, but keep the same sulfite as Xtol 1+3 (or any 
>other favoured dilution).  This is great for films like TMX and Acros that 
>run out of developer in Xtol 1+3, or for pushing TMZ.
>
>Of course the other option is to mix the patent formula Xtol and addboric 
>acid until the pH of the stock is 8.2, but you may also run into problems 
>with 'photo grade' chemicals.  I really don't think the EDTA alone is 
>enough to chelate ions out of the chemicals or water.
>
>Also look at US patents # s 3658527, 5376510, 5503965, 5738979, 6110655, 
>6489090, 6673528 and 6686135 in addition to the Xtol patent 5756271.
>
>I hope this explains a few things and is interesting.
>
>Marty
>
>
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Chris Saganich, Sr. Physicist
Weill Medical College of Cornell University
New York Presbyterian Hospital
chs2018@med.cornell.edu
Ph. 212.746.6964
Fax. 212.746.4800
Office A-0049