Here's a link to the Kodak chemistry site that deals with process control. If you go the processing manuals section, you can get to pdf versions of the Z books. They explain how to set up your process, use the control strips etc. and there's also info on that site about dealing with low volume usage for the chemistry.
fwiw, control strips are pre-exposed film or paper from the manufacturer. they come in emulsion lots just like film does. kodak ships theirs same day packed in dry ice or packed with one of those frozen gel bags . you get them & store them immediately in a freezer, and every day you just pull out what you need. The box , comes with a reference strip that you read & apply certain factors to (for the emulsion of the strip)--these are the values you aim for and check your daily plots against.
</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (tschmid @ May 14 2003, 04:06 AM)</td></tr><tr><td id='QUOTE'>it seems to be a better approach to replenish timely than to adjust filtration.</td></tr></table><span class='postcolor'>My sentiment as well.. why also so-called constant developers and/or replenstishment of some sort too is appropriate to B&W chemistry.
</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (tschmid @ May 14 2003, 04:06 AM)</td></tr><tr><td id='QUOTE'>In my understanding, a control strip is a well-known pre-exposed piece of paper that is analyzed with a densitometer. A test strip is more or less an indicator if something is ok or not. I sometimes use test strips to check if my BX is still ok (which is not that easy to determine as CD)</td></tr></table><span class='postcolor'>This is where the Lici/Jobo ColorStar (and its Jobo's patent montebank mutation as Colorline] comes in very nicely. By examining the calibration prints made on the same batch (no need really for frozen specimens since the printing paper is not the same and one is looking to get good prints with a "wellknown" batch of papers and chemistry and not standardized process control) against a colour reference card--- a reflective colour densitometer is nice but not really demanded by this regime--- one can see monitor, control and adjust the chemistry accordingly.
</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ed Sukach @ May 14 2003, 05:46 AM)</td></tr><tr><td id='QUOTE'>Thank you for alerting me to the "latest" from Tetenal.</td></tr></table><span class='postcolor'>
What's also very interesting is the observation that all the NP ("No Plumbing" or waterless) sets are reserved for commercial and the amateur sets demand water.
Super-Stabilizers like Tetenal's STAB-WL not only brightens up the paper a bit and replaces the need for watering ("No Plumbing") but even, according to vendors, **increases** the archival qualities. its perfect for the 4th slot in a Duolab or Nova Quad and even the wash slot (instead of water) in a Nova Club or TriRapid.
The downside is that the typical unit of sale is enough concentrate for 100 liters or more.. which again.. looking at the replentishment rates that's a whole lot of stab.
Which brings us full circle, again, to the inital point of question.. How long can these concentrates be stored. A mini-lab may run through many liters in no-time flat but I'm quite far removed from being a "mini-lab"..
I recently (last week) opened a "reserved" set of Tetenal (JOBO) RA-4 Chemicals - Half-full bottles opened on 4 September 2002 and preserved with my dwindling supply of "Protectan" spray; stored at ambient darkroom temperature. All chemicals are *fine*. Test strips (ColorStar type) indicated *very little* sensitivity or color balance shift.
I *really* like the Tetenal chemicals - for both their longevity and results.