[Leica] Long Xtol rant

[pmcc_2000 at yahoo.com (pmcc)]

Many thanks Marty.  Your posting was interesting and
helpful even to a non-chemical DIY'er such as myself. 
You've inspired me to get out the hazmat gear, roll
down my sleeves and go to work.

Next question:  can you point to or have you derived
dev'pt times for Xtol at various dilutions -- 1:2 and
most particularly l:3 -- for various common films? 
Higher dilutions don't appear on the product data
sheet.  I've seen frequent discussions of the manifold
benefits of higher dilution, and it would be great to
have specifics for starting points.

Peter.
SF, CA

P.S.  Hey, this is a non-digital thread -- feels like
Y2K.


> 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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