Cause of white precipitate in fresh XTOL stock solution?

I've observed the white precipitate in XTOL on many occasions but hadn't checked on emergence time. Well, yesterday I mixed up a fresh batch of XTOL in steam distilled water, thoroughly mixed at the correct "room temperate" - warm at the moment in the UK - and the solution was completely clear, afterwards poured into a 5L plastic developer bottle. Returning less than 24 hours later, the XTOL is now showing the classic white precipitate that has been reported on many occasions, here and elsewhere. I'm not sure however if I've ever seen reported what causes this precipitation to occur?

Warm up the developer to 85 degrees or 90 degrees F and stir to get as much back in solution as possible. Whether you do it or not, the XTOL will work.

I can offer no explanation* of how/why the precipitate forms. However, I've never mixed a 5-liter batch of XTOL (always using steam-distilled water) that didn't have it after as little as 24 hours.

My approach is to accept the precipitate as a reality, much like anthropogenic global warming, and deal with it. I store five liters of XTOL stock in 20 250ml amber glass bottles, each one used one-shot for a single developing run. A Paterson funnel, set into my graduated cylinder, is lined with a white coffee filter, and the XTOL poured through that. After at least 15 years of using this method, I've never seen any detectable precipitate residue or other deleterious effect from it on negatives. The XTOL has worked in a sensitometrically consistent way after being stored in those full glass bottles (with Teflon-lined caps) for up to one year.


* If your chemistry curiosity is high, perhaps the inventors of XTOL, Dick Dickerson and Silvia Zawadski, can satisfy it. A bit more than seven years ago, I was concerned about continued XTOL availability after Kodak's bankruptcy, and asked them to assess my plan for long-term storage of dry XTOL packages. They were most helpful and responsive. At the time, and as recently as five years ago when I had another XTOL question, they could be reached at:

Sal Santamaura said:

I can offer no explanation* of how/why the precipitate forms. However, I've never mixed a 5-liter batch of XTOL (always using steam-distilled water) that didn't have it after as little as 24 hours.

My approach is to accept the precipitate as a reality, much like anthropogenic global warming, and deal with it. I store five liters of XTOL stock in 20 250ml amber glass bottles, each one used one-shot for a single developing run. A Paterson funnel, set into my graduated cylinder, is lined with a white coffee filter, and the XTOL poured through that. After at least 15 years of using this method, I've never seen any detectable precipitate residue or other deleterious effect from it on negatives.

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I've started filtering my XTOL through a coffee filter now I'm using it replenished as the build up of processing residues makes the precipitate more obvious. I'm not yet completely sold on XTOL replenished vs 1+1 dilution in my Jobo machine, but time will tell.

Tom Kershaw said:

I've started filtering my XTOL through a coffee filter now I'm using it replenished as the build up of processing residues makes the precipitate more obvious.

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I do the same. I have a 10 liter ( almost 3 US gallons ) canister with replenished Xtol that has been working for over three years. There is allways some precipitate on the bottom but if you filter the amount you need for each developing session, there won't be any problem. See to that there is no air at all when you close the cap and mix new developer with deionized/distilled water and you have the best developer available.
Karl-Gustaf

Have no problem with Xtol but I do get white flakes of something with the gallon size Dektol, I use distilled water.

I had an interesting experience years ago. I used to dissolve Ilford powdered fixer in Melbourne tap water (which is fairly low in dissolved minerals). The fixer thereafter wasn't as clear as the water. After a few days, there always appeared some grey cloud-like impurites near the bottom of the gallon glass bottle. The liquid above was quite clear, and I used to decant some off for film use, and the rest was used for paper. Years later I obsessively bought a Fisons electric steam distiller and made distilled water. When the powdered fixer was dissolved in it, it initially showed the same slight turbidity, but what was interesting is that it never settled, ever. Same bottle, same storage etc.

I mix Xtol double strength (half the volume to store) in previously boiled Melbourne tap water and have never seen a precipitate. (It does take some dissolving!)