Archived posting to the Leica Users Group, 2007/07/25

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Subject: [Leica] Long Xtol rant
From: freakscene at (Marty Deveney)
Date: Wed Jul 25 05:44:04 2007

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.  It’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 

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:
 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 buffer, 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 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 

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.


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