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Steven Ruttenberg
7-Feb-2019, 19:45
Faucet it is 7.56 from RO it is 6.46. Kinda large swing. Faucet is base and RO is acidic. Hmmm

Steven Ruttenberg
7-Feb-2019, 21:12
My Kodak stop bath mixed with RO water is 2.56.

Peter Collins
8-Feb-2019, 10:44
Steve, why is your RO water NOT pH 7? If it is high-megaOhm water, it should be 7. 18 megaOhm RO water is used by env. labs using EPA test methods. Required. I know, I worked in one. High megaOhm means it has nothing in it to affect specific conductance.

Now, for something completely different: developer, stop bath, and fixer pH likely not a significant variable. Processing time, developer solution temperature (AND temperature change DURING development if times are 8 min plus) more significant. Stop is stop and fixer is just, well, fixer.

Steven Ruttenberg
8-Feb-2019, 13:49
I don’t know why the RO is slightly acidic All I can think of is filters are 2.3 years old.

koraks
8-Feb-2019, 13:58
developer, stop bath, and fixer pH likely not a significant variable.
Developer pH is, within certain margins, very significant. A +/-0.1 difference isn't likely to have much effect, but a +/- 0.5 or greater difference can produce problems. With commercially packaged developers, I personally always assume that they are sufficiently buffered and formulated in such a way that they are fairly insensitive to differences in the water supply. This, however, is certainly not the case with home-brew formulas. I use these a lot and I find that establishing the correct pH is essential in some cases. For example, instant Mytol (DIY XTOL alternative) formulas give me (YMMV) way too low pH when mixed according to the published formulas and I need to adjust them to the correct pH of 8.2. The same with the Bonavolta C41 formula which I use a lot and which gives again a way too low pH if the recipe is followed, and it needs to be adjusted upward to get correct gamma and color balance. Evidently, pH is more important with color than with B&W, but it proved to be enough of an issue with the Mytol example to produce unprintable negatives without adjustments.

pH of stop and fix are indeed of lesser importance and there is significant leeway in those cases (except for color work, where the pH of the fixer really should not be below 6.5 to prevent leuco dye formation).

Leigh
8-Feb-2019, 14:05
What's RO ? ? ?

- Leigh

djdister
8-Feb-2019, 15:51
What's RO ? ? ?

- Leigh

Reverse Osmosis filter.

Leigh
8-Feb-2019, 15:53
Reverse Osmosis filter.Why would that change the pH?

I thought it meant Ruthenium Oxide.

- Leigh

djdister
8-Feb-2019, 16:32
Why would that change the pH?

I thought it meant Ruthenium Oxide.

- Leigh

From the interweb:

Reverse osmosis water purifiers will reduce the pH of drinking water. Because reverse osmosis removes the minerals in water the water will then react with carbon dioxide upon exposure to air to form carbolic acids, thus lowering the pH.

Leigh
8-Feb-2019, 16:40
From the interweb:

Reverse osmosis water purifiers will reduce the pH of drinking water. Because reverse osmosis removes the minerals in water the water will then react with carbon dioxide upon exposure to air to form carbolic acids, thus lowering the pH.
OK.

If that's a known effect, I don't understand why the OP asked about it.

- Leigh

David Lindquist
8-Feb-2019, 18:03
From the interweb:

Reverse osmosis water purifiers will reduce the pH of drinking water. Because reverse osmosis removes the minerals in water the water will then react with carbon dioxide upon exposure to air to form carbolic acids, thus lowering the pH.

That should be carbonic acid, carbolic acid is an old name for phenol. Maybe being a little nit-picky about mis-speaking-mis-spelling but we are talking chemistry here.

David

djdister
8-Feb-2019, 18:28
That should be carbonic acid, carbolic acid is an old name for phenol. Maybe being a little nit-picky about mis-speaking-mis-spelling but are are talking chemistry here.

David

Thanks, I need to steal from a better website...

Maris Rusis
8-Feb-2019, 18:37
For the point of view of electrochemistry, an old laboratory specialisation of mine, it is theoretically impossible to measure the pH of pure water using a glass electrode. The hydrogen (and hydronium, etc) ion strength and ion mobility is just too low to arrive at a stable result. Interference from dissolved gases (CO2 mainly), temperature gradients, and assymetric flow, drift, and diffusion across the glass electrode, and contamination from the electrode itself, masks the result. That's why pure water is characterised by conductivity measurements rather than PH with 18.2 megohm water being theoretical perfection. Just dipping a PH electrode into ultrapure water destroys it in seconds.

Less pure water with plenty of mobile ions in it can be characterised by a PH value measured with a glass electrode BUT anything remotely like potable water is still a solution so dilute that it has no buffering capacity. The result of this is that it doesn't practically matter what PH water you start with. The starting water PH is totally (totally) overwhelmed by ions you dissolve in it when making up photographic processing solutions.

Steven Ruttenberg
8-Feb-2019, 20:21
I agree,but the point of measuring my water was to ensure it was not the culprit causing my issues with minimal agitation using pyrocat over 1 hour. It turns out the particular film I was using doesn’t like that process.

Steven Ruttenberg
8-Feb-2019, 20:24
OK.

If that's a known effect, I don't understand why the OP asked about it.

- Leigh

Because I didnít know..When I donít know about something I ask instead of assuming. Also, our installer did not mention that fact. Why didnít you know what RO meant? :)

pepeguitarra
8-Feb-2019, 21:56
Faucet it is 7.56 from RO it is 6.46. Kinda large swing. Faucet is base and RO is acidic. Hmmm

Is your water mostly coming form the Colorado River? Very high in salinity. Maybe that is why you have RO system. RO does not use filters, they use membranes, which is a bit different. Membranes use to last 5 years max 25 years ago. Nowdays, they may last 20 years. They do need cleanup once in a while. You can put some sodium bicarbonate to make it more alkaline. Pepsi and Coke's pH is 2.53. Very acidic. People use Coke to clean the toilet in lieu of DraŮo.

Steven Ruttenberg
8-Feb-2019, 22:24
Coke is used to clean rust to. Water comes from Salt River. This system has 3 cartridges that is supposed to be replaced at certain times. The tank is 4 gallons I think. One of the cartridges is a membrane. Water first goes thru a water softener that is salt. Was suggested to switch over to potassium. Not sure if being slightly acidic is a big deal though. Guess it depends on the pH level of developer after mixing up. One reason I think it needs replacing is ppm is supposed to be zero but it is at 22ppm. Out of regular tap it is 420ppm. Total salt is 19.8. Almost zero.

Peter Collins
8-Feb-2019, 22:34
Steve--
It's the membrane cartridge which is critical to the final result. The other filters in the 3 filter system need to be changed, too, but if the membrane filter goes, you get unsatisfactory water. Some systems state that 10,000 gals is the trigger for changing, but I think that is optimistic in some western water supplies. (I found Albuquerque water MUCH harder than Southeast MI well water.)

If you are on a city water supply, you might ask what the TDS--total dissolved solids--is in the "finished" water. If you get a chemist technician's help, you might ask water the Specific Conductance is. With this value I might be of some help re life of the membrane filter.

Steven Ruttenberg
9-Feb-2019, 08:44
The water out of my faucet no RO or anything is 442ppm. I can measure the resistance of water and get back to you. I will also call water co and see what they say.

pepeguitarra
9-Feb-2019, 09:09
The water out of my faucet no RO or anything is 442ppm. I can measure the resistance of water and get back to you. I will also call water co and see what they say.

Steve: Water at 0 mg/l or 0 ppm (pure H20) is very corrosive, it has been deprived of all minerales, so it will tend to "suck" or steal minerals from whatever it can. Even at seawater desalination plants, where they can go down to 50ppm, they will blend with other water to raise the mineral content. In Southern California, we get water from the Colorado River at 700ppm, sometimes the water district mix it with water from Northern California (150ppm) to give us a blend 500ppm. When we get 500ppm were are happy. I use water from the refrigerator, which still is at 500ppm, but the carbon activated filter will remove the ammonia or chlorine residual in the water.

pepeguitarra
9-Feb-2019, 09:26
Hard water is alkaline water. There is a trend now to drink alkaline water, they sell machines that create alkaline water and sell for a lot of money. Some of the same people who has a treatment water system at home (softening+RO) usually buy the alkaline water machine (when they could have drank the hard water in the first place). Usually softening (removing of Calcium and Manganese) is done before the R.O. because membranes cannot handle removal of Ca and Mg too well without clogging. The problem is that softening is done by a process called ION Exchange (IX) in which salt is added to exchange and replace Ca & Mg with Sodium. Those salts are later eliminated creating a high concentration of salt in the sewer, rending the sewer impossible or very expensive to be reclaimed and recycled. That is why water softeners are banned in many areas of California. By removing the Ca & Mg, the water becomes acidic. That is why when some people use it for stop bath, it works. I have not studied the effect of an alkaline developer will have on the water itself. I guess that using hard water (alkaline water) may accelerate the development time of film. Will you have to reduce the developing time? I am not sure of this, but I will look into it.

PS: Most home salinity removal system sellers do not tell you what is the TDS (total dissolved solids or as we have been calling it ppm) in the final water. Some buyers think they are getting 0ppm, which is impossible for health purposes. I will be interested in hearing what is the TDS of the water at the faucet (in ppm or mg/L).

Steven Ruttenberg
9-Feb-2019, 11:58
Mine is 440ppm at faucet 22 after RO. Water at faucet is slightly base about 7.4 out if RO 6.4. I am considering switching to potassium system

pepeguitarra
9-Feb-2019, 15:08
With TDS at 22 ppm, the water must taste really good, you must be saving a lot in soap. In the best days, I get 500ppm at the faucet, I don't have RO, I worked for the water district and trust my water, so I drink it straight from the tap. I usually buy Distilled Water from Walmart ($0.94/gal) for mixing my chemicals. I wash the film with tap water, but the final wash with kodak flow is with distilled water. Whenever I run out of Walmart water, I used tap water that has gone though the refrigerator, just because it removes some of the residual ammonia. I don't think switching from sodium to potassium will make a big difference, Potasium (K) and Sodium(Na) have the same valence in the Periodic Table, remember (K, Li, Na, H, Rb). You may want to try a test using the water delivered by the water company (440 is not bad), the water will be alkaline and maybe more stable with the developer. Disolved solids will not probably react with the silver, so I don't think there would be a reaction there. And because the TDS is DISSOLVED solids, they will get out with the final wash, not stay on the film.

Steven Ruttenberg
9-Feb-2019, 15:15
Good discussion. The water at my work where we use environmental chamber with heat and humidity has 220ppm and it destroys the little brass bowls and fittings. Nasty deposits. I just tested it.

The water from RObtastes awesome. In fact, my wife will not drink any other water, even if she is dying of dehydration. Short of distiller, I doubt I can get less ppm. I will see this water to mix developers and rinse with tap water. Photoflo I use the RO water as well.

I suppose I could treat water to raise the ph level to 7 before using it for mixing chemicals.

pepeguitarra
9-Feb-2019, 17:33
I think the recommendations by the manufacturers has to be strict and done based of neutral water, etc. However, after a while, we learn that those temperatures, and exactness on the solutions can be approximate. For example, I found out that one 35mm roll, one 120mm roll, and one 4x5 sheet of film will use 3.5 mL of rodinal for stand development. So, what I do is put in a tank 4 or 6 sheets of 4x5 (mixed up, e.g., Kodak 100Tmax, delta 100, Max 400, etc.) and pour a solution that has 3.5x6 sheets (21 mL) of Rodinal, and the remaining (979 mL) of distilled water (or water from the fridge) (I use the Jobo tank that has a full capacity of 1,000 ml to cover the 6 sheets). I don't measure the temperature, I know is around 62-to 72F. I agitate for one minute and let it sit for as long as I can. I try to come after one hour, or two, or three. One day, I left it overnight. Come back, fix it, wash it and done. They all come back just fine.

Leigh
9-Feb-2019, 17:50
I found out that one 35mm roll, one 120mm roll, and one 4x5 sheet of film...
Those are not equivalent.

Equivalence is whatever you can proof on a single 8x10 sheet of paper.
So it's one 35mm roll, one 120 roll, or FOUR 4x5 sheets.

- Leigh

pepeguitarra
9-Feb-2019, 21:14
Those are not equivalent.

Equivalence is whatever you can proof on a single 8x10 sheet of paper.
So it's one 35mm roll, one 120 roll, or FOUR 4x5 sheets.

- Leigh

I stand as corrected. Thanks.