How to expand Xtols shelf life

[bernhard]

Hi guys,

 

I'm a big fan of Xtol, but use it only occasionally, so it usually

dies before I can use most of it.

 

Is there a way to make it live longer, except storing it in the dark

in an air free container, which I already do?

 

Is it more stable when the 2 components are dissolved separately and

only mixed right before use?

 

Is there anything I can add to preserve it?

 

I work in a chemistry lab, so I know how to handle chemicals, have

access to equipment like scales or pH-meter and can get additional

chemicals if needed.

 

I can also refrigerate or freeze (-20?C, -80?C and liquid nitrogen) it

but I don't know if this helps or rather hurts.

 

Any suggestions wellcome.

 

Thanks

[ronald_moravec1]

Unless you drop one of those obnoxous purple pills into it, I think you pretty much have it.

 

Try mixing the the next batch in 2.5 liters instead of 5. It will mix in and you dilute for use.

 

Curious how you know when it goes bad. I got burned with week old stuff and have been leary ever since.

[frank.schifano]

Keep the air out of the bottle and you should get at least the 6 months that Kodak says you should. Refrigerating or freezing might not be the best idea. In any case, I've never found it necessary. I use empty soda pop bottles and fill up any extra air space with a shot of propane. Pick the inert gas of your choice. I mixed my last 5L batch of XTOL last October and it is still working well.

[gerry_szarek]

Your other option for keeping the air out is to use clean glass marbles availble from Walmart, Kmart, etc.

[jim_appleyard]

You can also mix your own according to the recipes in Anchell's "Darkroom Cookbook". The 1 liter solution will cost you pennies and if if dies, no big deal.

[dxphoto]

You can go to your local pharmacy stores and ask for various sizes bottles. There are made from PETE (same as soda bottles) plastic so they are good for developers. they came with 2,4,7,8 ozs sizes.

 

Like the wine, the bigest enemy to developer is the air, not the temperature.

[patrick_gainer]

Get some ascorbic or erythorbic (AKA isoascorbic) acid. Make sodium ascorbate or erythorbate by adding 1/4 gram of baking soda for each gram of the acid to a very small amount of water. After effervescence subsides, add enough of the mixture to the Xtol stock to be equivalent to adding about 4 grams of ascorbate per liter.

 

It is the ascorbate in Xtol that is oxidized. An excess of ascorbate makes little difference in the activity of fresh Xtol, but acts as a self replenisher. See the article at www.unblinkingeye.com about synergism between phenidone and ascorbic acid.

[dimon_.]

Guys,

can u tell me more how you remove the remaining air from the bottle with "a shot of propan" ?

 

So far I tried to squeeze the bottle and when liquid is almost flowing out, I close the cap. However! there is always at least 1 cubic sm of air always left inside. Shall I worry about 1 cubic sm

or just disregard it ? Can I do better with glass balls or propan ?

 

Thanks!

D.

[neal_wydra1]

Dear Bernhard,

 

I store Xtol in 250ml and 500ml bottles filled to the brim and use it as a 1-shot developer. While I normally use it well before the Kodak suggested 6 months, I have kept it for over a year this way without problem. As you work in a chemistry lab, you should have no trouble finding a good source for such bottles.

[bljkasfdljkasfdljskfa]

Air-evac (Falcon, or Kalt makes them, available from Adorama, etc.) one gallon bottles work well for the 5 liter Xtol. I store the 5 liter Xtol in a gallon air-evac bottle. This is not a standard stock dilution, but I use it as standard, and really don't notice a difference.

[big toys are better]

First of all, AVOID LIKE THE PLAGUE any vigorous agitation while mixing so as to prevent the introduction of air into the liquid, and if at all possible, degas the distilled water (yes, use distilled) either by heating to the boiling point well prior to use (then carefully cooling) or by depressurization (w/vaccuum pump). Putting nitrogen in the mixing container during mixing will surely help as well (sounds anal but there are obvious physical chemistry reasons behind this-- AKA diffusion). Degassing again by vaccuum pump would rid the last of any dissolved gases from the solution AFTER it is poured into its storage container (GLASS!), then add nitrogen to top off the container.

 

YUP, lots of work but also the surest way to keep the O2 out! Too bad someone doesn't make an oxygen scavenger for bottled solutions, maybe like an isolated steel shaving "brillo pad" capsule carefully placed well above the solution and there to preferentially rust away the free O2.

[andrew_hull]

I use coca cola bottle filled to the very brim. As you use the developer move down in size from 2 Litre, to 1 Litre to 750mL bottles and squeeze the sides of the bottles before putting the lid on and bring the level of developer up to the very rim. I have had Xtol last well over a year doing this.

[henry_a]

How long do you want it to last?

 

I keep my Xtol in full glass bottles with as little airspace as possible. Although I usually use a batch up in about 4-6 months I have kept it over a year with no failures at all. A large number of my bottles are small, one shot size for one roll of film, holding 125ml. When enough of them are empty I refill from totally full one liter bottles.

 

The advice about careful mixing and not whipping air into the distilled water is good. I don't go as far as that poster suggests but I am careful to use distilled or RO water that has been still for some while before mixing. And I did read that you know how to mix chemicals but be sure to be careful about the temperature and to wait for part A to dissolve completely before adding part B. Be sure your mixing vessel is clean when you start. I follow similar basic procedures for all my photo chemistry.

 

The other thing to remember is that 5 liters of Xtol is really cheap so if you think it might be bad just toss it and mix some fresh, but careful mixing and storage is the best answer.

[bljkasfdljkasfdljskfa]

R. Hofland: FUD about degassing. The stuff is cheap. Not worth the effort degassing distilled water, and not necessary.

[mike_rosenberg1]

Patrick,

 

I have often wondered about adding ascorbate to xtol as a replenisher. I assume that it would work for Na-ascorbate, that is not having to convert ascorbic acid to the Na-salt??? And do you know how long this will then last?

 

Thanks,

 

Mike

[melvin_bramley]

I have just developed,20 mins ago,a roll of Ilford FP4+ in Xtol. The results are just fine.When was it mixed? Sept/04.It's shelf life is just one of the reasons I use it.As has been recommended divide the powders in half if you want it to last forever!

[bernhard]

Wow guys, thanks a lot for all the suggestions. As everyone seems to agree that that getting rid of air to prevent ascorbate oxidation is key that's what I'll do.

 

Thanks a lot.

[big toys are better]

Dan, as I implied, the strict degassing regimen was an anal solution, as are some of the other extremes, but removing as much of the dissolved gases as possible prior to mixing and afterwards if possible is the best way to provide long-term stability of an oxygen sensitive chemcial. That and keeping any new infiltrations to a minimum. This seems to benefit XTOL.

 

BTW, the careful degassing of solutions is an absolute necessity in certain high resolution HPLC chromatography techiniques as even small amounts of dissolved gasses can dramatically alter results. Not that we in photography need to be quite so exacting....

[steven_b.]

Floating lid tank - it has been working great for me.

 

All of these elaborate techniques seem a bit much if you ask me.

[bernhard]

but as I got a vacuum pump on my bench, why not degas?

[jan_brittenson]

I always test XTOL before use. Throw a leader into a cup with some developer at working dilution (I only use it stock), and slosh about a little every once in a while. In about 5-6 min (for stock) depending on room temperature it should be uniformly developed. Then rinse off the leader under a faucet and test the fixer while at it.

[eric merrill]

I store Xtol in small brown 250 ml bottles stored in the dark. Filled up to the very top. No air space on top. I've had success using xtol that was over a year old...that's the longest it has taken me to go through a batch. Usually, I use it all within 6 months or so.

 

I use Xtol 1:3 in a liter tank, so the bottles are one shot. I open, use, and then wash and store the bottle for the next batch.

[patrick_gainer]

While we're on the subject, I've done some calculations to try to find out what we worry about. The solubility of oxygen in water is on the order of 4 cc /liter at standard atmospheric pressure. The density of oxygen at that pressure is 0.0014 g/cc, so we can dissolve about 0.07 grams in a liter. What happens to this oxygen when we add ascorbic acid or an ascorbate? One atom of oxygen combines with one molecule of ascorbic acid to form one molecule of dehydroascorbic acid and one molecule of water. Dehydroascorbic acid is slightly more acidic than ascorbic acid, so the pH is slightly reduced. If I did my calculations correctly, 16 grams of oxygen make 176 grams of ascorbic acid unavailable for developing film. Thus, the oxygen we could dissolve in a liter of water can eliminate 0.77 grams of ascorbic acid (or the isoascorbic acid which Xtol uses). Perhaps the best way to scavenge the initial oxygen is to add a little sodium ascorbate to the water before mixing. It is a better scavenger than sulfite.

 

There still remains the possibility of introducing oxygen to the developer during or after initial mixing. The amount of oxygen that the developer solution can take up is probably much greater than the amount that can be dissolved in plain water. After all, that is what ascorbates were designed for by Mother Nature. If you are going to use diluted developer, it might be a good idea to add a little ascorbate to the diluting water. About a gram per liter should be enough, and the amount will not be critical. If, as I suspect, the ratio of ascorbate to dimezone (or whatever) in XTOL is at or near the plateau of synergism, 1/4 teaspoon will do.

[ryuji_suzuki]

Patrick, you're writing an embarrasingly naive and incorrect view of developer oxidation.

 

Ascorbate is not a good scavenger of oxygen in water. In absence of impurities the rate of oxidation is VERY low. In presence of catalysts the rate can be hugely increased. This is the problem.

 

When the impurities are present, the whole picture is a lot more complicated than a simple redox reaction. Besides molecular oxygen and peroxide, things like superoxide, hydroxyl radical, etc. can get involved at some point in the chain of complicated reaction.

 

The correct way to deal with this problem is to design a developer so that the catalysts are inactivated and the chain of potentially self-amplifying oxidation reactions do not happen. It's nothing like simply increasing ascorbate in the developer.

 

In addition, I have to mention that your suggested addition of ascorbate to an existing developer like XTOL would disturb the pH of the developer solution from what it is designed at, thereby affecting the photographic activity of the developer. This is a separate problem from the rate of superadditive development, which is discussed at a constant pH condition.

[anders_br_the]

Patrick; From your numbers 70mg O2 can be disssolved pr liter water. If all or part of this is consumed in oxidation, more O2 from the air is free to dissolve. This is an equilibrium. The amount of O2 dissolvable pr liter water will merely dicatate the speed of the oxidation, not limit it unlesss one keep the solution in oxygenfree conditions.