A very good point Jerry. It is a matter of equillibria and nothing can stop this, it can only be slowed down.
A few weeks ago, I had a nice concentrate that matched XTOL in all respects -- density-curves, grain and even dev-times. But that work was halted when I discovered that the concentrate crystallizes and separates. This occurred with DimezoneS but not Phenidone, so I was back to using Phenidone. In that formula, using Phenidone was slightly grainier than DimezoneS.
After more experimenting, I've come up with the formula below. Its grain is slightly better than XTOL, sharpness is the same, and dev-times are longer. The 1-litre formula for mixing directly into water:
Sodium sulfite ................. 45 g
Sodium metaborate ........ 2 g
Ascorbic acid .................. 4.5 g
Phenidone ...................... 0.05 g
Target pH = 8.05 to 8.10.
13:40 minutes for TMY2.
For a concentrate, mix everything except sulfite into 16 ml of propylene glycol.
Here's the density-curve compared with XTOL, which is a perfect match:
Grain looks a tad better than XTOL in my 22x loupes. Here are full-resolution crops of neg-scans of XTOL (left) and concentrate (right):
An objective way to gauge grain is by the sizes of JPEG files, keeping dimensions and contrast identical. Finer grain (textures) produce smaller files. In the crops above, the concentrate's files are 2.25% smaller.
The sharpness of the high contrast horizontal line looks the same to me, but the low contrast vertical lines look a bit softer for the concentrate. Shutterspeed was 1/8 second (tripod), but there still might have been a bit of horizontal vibration. I'll have to watch future test-strips.
I discovered this formula back in February and posted it to apug on Feb 5, 2012 here. But I was investigating the effect of sulfite, and didn't pursue this discovery.
There's still much experimenting I want to do, varying ingredients by small amounts and gauging the effects. But I wanted to post this because it's a good milestone and will be my baseline for further work.
Hmmm.... I routinely store Xtol in full 1 liter bottles in a fridge. I take them out several days before I use them. I haven't noticed any obvious problems in my negatives from doing this, but I didn't know that the sulfite precipitates out. My bottles aren't clear, so I wouldn't be able to see it. I'm not really a chemist, but doesn't sulfite act as a preservative? If so, then the fact that it precipitates out doesn't sound like a good thing. Also, I'm guessing that the lower sulfite level might impact the apparent size of the grain.
Originally Posted by albada
As a result of your posting, I put a 1L bottle of XTOL in the fridge last night. This morning, it had a thin layer of precipitate on the bottom which, upon disturbing the bottle, broke up and floated around in the fluid, looking like pieces of shredded tissue. Both of my prior batches of XTOL have done this at room temperature over a couple of months, so refrigeration sped-up that process. I'm leaving it in the fridge to see how much precipitate forms.
Originally Posted by Dave Krueger
I have seen this as well. I've been using my XTOL replenished so I had thought it might be buildup of some residue after many rolls, so I filtered it out. Have not noticed any effects one way or another from filtering.
Both of my prior batches of XTOL have done this at room temperature
Your developer looks really interesting. I've been watching this thread over the last few months and have gradually acquired all the ingredients. The last of my XTOL is gone now, so I'm going to be making up a batch of this formula to try it out.
So, looks like some great work you've done. Thank you for sharing!
All this has happened before, and all this will happen again.
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As a side note, I store 5L of Xtol using the same means as the box-o-wine.
The Fermtech "Wine on Tap" system consists of a sanitized oxygen barrier bag with a push-button dispensing spout and plastic shell that provides the "box" structure. The plastic shell and one bag costs about $23 and replacement bags are 3/$10.
After the Xtol is mixed, use a funnel to fill the bag and snap the push-button dispenser on. (Don't snap the dispenser on until the bag is full. It's meant to be disposed of with the used bag and nearly impossible to remove without damage.) Orient the dispenser on top and gently squeeze the bag while pushing the button to expel any air. There shouldn't be much. Then set it upright and you're good to go.
Dispensing into a graduated cylinder is easy with the push-button and the bag collapses around the remaining Xtol with no air pocket.
I have no trouble using 5L in six months, so I don't know how long Xtol will store this way. It should be good for quite a while, though.
Uh-oh.... I've seen that shredded tissue look before back when I was using amber glass bottles to store Xtol in the fridge. I thought is was some kind of residue from manufacturing the bottle. I figured it would be gone next time I used the bottles, but then switched to barrier bottles, so I completely forgot about it.
Originally Posted by albada
Dammit. And I thought I was being so clever by storing it in full 1 liter bottles in the fridge. Well, it's nice to know the truth anyway. I'll leave them out of the fridge from now on. Thanks for the insight, Mark.
This is a good idea!
Originally Posted by foto_mike
I would give you one caution though: You'll notice from nearby postings by kb3lms, Dave Krueger and myself that XTOL tends to form a thin film of precipitate on the bottom after storage for a few weeks or a couple of months. Since your tap is on the bottom, any precipitate will come out first. So if it's been a few weeks since you dispensed some XTOL, I suggest examining the beaker for bits floating around.
Is it needed to multiply the weight of metaborate by 1.354 (see post 85) if 8-mol metaborate is supplied?
Originally Posted by albada
Is there an approximate multiplier of Xtol time for development?
Once you dilute the Xtol to 1+1, the shredded-tissue stuff goes back into solution and it's all good. It's not good to use as stock because you'll get dense spots on the film.
I use the bag-in-box method, though I just buy a 10L box of drinking water (low iron, unlike our tap water), use that to make up the developer and put it back in the bag.
There is some oxidation in a sealed container due to oxygen already dissolved in the water. You could boil the water first to degas it but I just make my Xtol up at higher concentration (1.25x, i.e. 5L pack into 4L), which reduces the O2 content by 20%. I think I've seen a report on APUG that it will dissolve in 3L.