XTOL 1.32 gal in a 1 gal bottle?

[hpulley]

Yeah, I keep some 500mL around for just that purpose, best to keep the air to a minimum and you can use up the 500mL fairly quickly.

 

[michaelbsc]

... There might be several candidate processes, but the one that comes most readily to mind is to "mix" the components of the powder at the time of bag filling, i.e. to fill the bags from two or more streams of pure component. For sake of discussion let us limit this to components A and B. The problem then is to adjust the manufacturing process so the bag is always loaded with the same mass of component A. The same can be said of component B.

There would seem to be two ways of doing this, one based on mass measurement and the other based on calibrated flows of powder. For example, one could add powder A to a weighing pan, adjust the amount until it has the correct weight, and add it to the bag. Alternatively one could add powder A to the bag and weigh the bag, and assuming the weight of the bag was previously known, one would top off the bag with just enough powder to bring it up to weight. One would then to the same with component B. These mass-based processes would be expensive, though it might be possible to automate it to bring the costs in line with commercial reality, and in any case they would likely be "gold standard" methods.

The other way would be to add components A and B using some kind of calibrated flow streams, i.e. there would be a stream of component A of known flow rate and a stream of component B in another flow stream. They would be either added to the bag without any premixing, or the streams could be mixed just as or just before they are added to the bag. If mixed before being added to the bag one would need to be sure the streams do not settle into a heap before being added to the bags. Otherwise the components will stratify and we are back to the problem of uniformly sampling an inhomogeneous heap.

I should add that calibrating a flow stream would itself face a similar problem. Before a powder is introduced into a flow stream it must surely exist in a bin or a heap. To get a uniform flow from the heap (which has surely been stratified into an inhomogeneous sample with respect to particle size) would not necessarily be an easy task and would probably require constant monitoring of and tinkering with the flow stream controller.

It would be interesting to know what method Kodak uses for mixing their components and adding them to the bag.

I cannot tell you how the Kodak chemicals are packaged, but I can tell you from experience that both the mass weighing systems you describe and the flow rate systems you describe are commonly used in industry for similar powder dispensing.

Generally small quantities are weighed on a scale, with additional powders being flowed into the weighing chamber or bag using an auger or vane-type dispensing valve. 1 turn of the dispensing device gives fairly repeatable doses of chemical.

Intermediate quantities are usually dispensed with a larger auger or metering valve, but since the tolerance is wider (in terms of absolute mass, not necessarily wider in terms of percent) often it is not weighed. It is simply dispensed by so many revolutions of the shaft. Effectively the flow rate system you describe.

Larger quantities are again usually weighed like the small ones, and again dispensed with either an auger or a vane type rotary valve.

I should add that calibrating a flow stream would itself face a similar problem. Before a powder is introduced into a flow stream it must surely exist in a bin or a heap. To get a uniform flow from the heap (which has surely been stratified into an inhomogeneous sample with respect to particle size) would not necessarily be an easy task and would probably require constant monitoring of and tinkering with the flow stream controller.

It would be interesting to know what method Kodak uses for mixing their components and adding them to the bag.

The hopper usually is filled with powder of a known particle size, and that is screened using a vibratory screener. Check here: http://www.sweco.com/

The particle size consistency is important, that is usually controlled rather than constantly fiddling with the flow controller. Most controller manufactured within the past 70 years, since the 1940s, monitor and adjust themselves. Interested parties can look up PID controllers or three-mode controllers. Old ones were pneumatic. New ones are electronic.


It's actually not as mysterious nor as expensive as you would think after you've seen a few of them in operation.

None of this is the same for liquids.

Michael

 

[alanrockwood]

Michael,

That was very interesting and informative.

Thanks.

Alan

 

[2F/2F]

I'd drink five quarts of juice, rinse them well, and store the X-Tol in the five empty bottles. (Ocean Spray cranberry juice comes in useful bottles. They are thick and stable, and they have a good gasket.) For mixing it up, you can go to the local dollar store and get a cheap pot. You can scratch a few marks on the inside of the pot to mark the individual liters.

 

[fschifano]

I'd drink five quarts of juice, rinse them well, and store the X-Tol in the five empty bottles. (Ocean Spray cranberry juice comes in useful bottles. They are thick and stable, and they have a good gasket.) For mixing it up, you can go to the local dollar store and get a cheap pot. You can scratch a few marks on the inside of the pot to mark the individual liters.

I especially like the smaller round Ocean Spray juice bottles. The hold about 1.4L each, and I use them for storing working solutions for tray processing. That's just enough for the 11x14 trays I most often use. For mixing p powdered chemistry, I use a mop bucket sourced from the dollar store and a big plastic slotted spoon sourced from the same place.

 

[mrberns]

Has anyone actually had any problems personally with mixing xtol into a 5 liter container? I'm about to mix my first batch of it and would definitely like to keep it in a single container for less hassle. I tend to go through a gallon of D-76 every two to three months mostly doing oneshots of 1:1, and figured 5L of xtol shouldn't sit in there much longer than that. Only thing is when its down to the last two or three rolls worth, theres going to be a lot of oxygen in there. So just how quickly will it turn when it gets to that point?

 

[2F/2F]

My two cents is that the thought of possibly-inconsistent developer activity throughout the life of the solution would be much more of a hassle to me than using several small bottles.

Has anyone actually had any problems personally with mixing xtol into a 5 liter container? I'm about to mix my first batch of it and would definitely like to keep it in a single container for less hassle.

 

[craigclu]

This works for me.... Water in a 1 gallon glass thumb-hole jug, add the Xtol powders, cover and gently roll back and forth until dissolved (I then decant to smaller storage bottles). It goes into suspension quite easily and minimizes the forcing of air into the mix. I modify my dilutions from a simple spreadsheet table to equate to normal 1:1, 1:2 and 1:3 use from a normal 5 liter blend.

I tried pasting from my sheet but it wouldn't format but to 1 liter of working solution 1:0, start with 757ml, 1:1 start with 379ml, 1:2 would be 252ml and 1:3 works out to 189ml.

I may be wrong on Xtol, but in general, I've been led to believe that higher concentrations show better shelf life, too.