Is there a simple and accurate way of measuring the specific gravity of freshly mixed Xtol. Kodak states in their literature that the specific gravity of correctly mixed Xtol is 1.085 +/- 0.003 measured at 77 +/- 0.5 deg F. (25 +/- 0.3 deg C) at PH 8.2 +/- 0.05. The reason for the question is that I am one of the guys who has experienced Xtol failure more than once. I would simply give it up except that Xtol is a nice developer when it works. I have read a couple of comments in this forum lately that Kodak seems to have the problem under control. I have also had responses from previous postings suggesting that I should check the PH or somehow test the developer after mixing to ensure that it will perform properly. Again this seems like a step that is hardly worth the effort unless it is very simple and in fact works. Any comments? PS. I am no chemist so I have to stress that any test has to be simple.

-- Bill Lester (wlester@lesterconstruction.com), May 25, 2001

Answers

Che-a chemist with a pipewrench.

You can get a hydrometer (like you test antifreeze with) that makes a specific gravity simple to measure. However, the specific gravity doesn't really tell you much about the mix of chemicals in a multiple component solution. Seems that a clip test would do the trick, if you are worried.

-- Gene Crumpler, NC, USA (nikonguy@att.net), May 25, 2001.

ok, now here's a question i can help with (i'm usually asking them here)

anyway, if you want to do a very simple test for this all that is required is a small scale and graduated cylinder/beaker or something you can measure a known volume in... example using 100ml xtol at specified temperature: first get a tare weight of your cylinder/beaker then fill with the xtol to the 100 ml mark, now take your gross weight, subtract the tare weight... if you get 108.5 grams then you nailed it!

results can vary depending on accuracy of everything you use, use large amounts if more accuracy is wanted as small errors become less significant with larger test amounts

if you want to try other numbers remember specific gravity and density are basically the same but sg is dimensionless and you need to use metric units for this to work, density = mass/volume in units could be grams/ml so you can use what ever you need

as for xtol, i've tried one 1 liter pack for some high speed stuff and it worked very nicely for me, i did everything at 1:1 and will use it some more as i often have to shoot 1600-3200 asa

good luck joe

ps- if you want to check the pH you will need a digital probe (you can sometimes find them for reasonable price in fishing catalogs) as you'll never be able to tell close enough with pH paper

-- Joe H (joe1013_@excite.com), May 25, 2001.

Bill, this is a topic I have some familiarity with. I would say that Gene and Joe are both pretty much right, but Gene's advice is much more pertinent.

With a powdered mix like Xtol (no liquid additions), checking the specific gravity is really more of a check for mixing errors than anything. These errors are basically either 1) Kodak put the wrong amount of powder in the mix, 2) you used the wrong amount of water, or 3) you didn't get all of the powder to dissolve.

To put the specific gravity test in perspective, if a practical joker were to sneak into your darkroom, dump out the Xtol and replace it with an equivalent weight of sugar, for example, it would almost certainly still pass the specific gravity test. However, Gene's "clip test" would still catch the problem.

If you have a scale, like Joe suggested, you would probably be as well off to just weigh each package of Xtol and make sure they're within about 3 or 4%; then be careful that you don't make a blatant error mixing.

-- Bill C (bcarriel@cpicorp.com), May 25, 2001.

Any body up for a little Thermo:)?

-- Gene Crumpler, NC, USA (nikonguy@att.net), May 25, 2001.

Yeezzz...if you have to go to all that trouble, why not mix your own?

-- Jorge Gasteazoro (jorgegm@worldnet.att.net), May 26, 2001.