Donald Qualls wrote:
Jean-David Beyer wrote:

Dale Strouse wrote:

It could be that the distilled water you are using in your final
rinse/wetting agent (distilled water) has minerals that upon drying
are being left on the film surface.



How much mineral content could _distilled water_ have?


Depends how it was handled and stored after distillation. Water can
pick up sodium from glass,

I suppose so, but sodium ion is very soluble and unlikely to precipitate
out onto the film.

and ultrapure water will actually attack glass and etch it in much the
same way strong hydroxide solutions can.

Much slower, though.

If stored or transported in metal, the water may dissolve metallic
oxides or hydroxides.

I have never seen distilled water transported in metal. If I buy
super-market distilled water (being careful not to get simply
ion-exchanged softened water), the stuff nowdays comes in plastic bottles.
I have more confidence in the glass bottles.

But I do not buy that stuff. I condense a lot of water out of the air here
in New Jersey with my dehumidifier and then filter it and store it in
glass bottles. Dehumidifier water certainly needs to be filtered as it can
pick up a lot of dust -- though the dust mostly sticks onto the evaporator
tubes. I would never drink the stuff. I probably get enough to wash films
in it (though not with my normal washing methods), but I do not do that. I
wash in tempreature-controlled filtered tap water. The final rinse in weak
PhotoFlow is mixed from filtered dehumidifier water. This is good enough
for 35mm negatives and, of course, larger sizes.

If the distiller is overdriven (in an attempt to increase production
rate) minerals may be carried over from the supply in droplets (as
opposed to pure vapor transport from supply to collector). And,
depending on the content of tap water used in earlier stages, a single
rinse in distilled water may be insufficient to remove minerals
deposited by the tap water.

My water was so crappy that I got all kinds of crud on negatives.
Installing 20 micron filter fixed this. When I got a better-designed mixer
valve, I went to 5 micron filters on general principles. I recognize that
these filters are useless against dissolved minerals, but they sure work
on the lumps and chunks.

[snip]

Another advantage of distilled or filtered water -- stored with your
chemicals, everything is at the same room temperature, and there's no
concern about reticulation or fussing with the taps to adjust the water
temperature -- just pour from the jug, and it's ready to go.

I process film in my Jobo, and all water used goes through a Lawlor
pressure balancing and thermostatically controlled valve, so everything is
at the same temperature anyway. I have never seen reticulation, though I
know it can be achieved, especially with older, less hardened, films.

--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 23:50:00 up 5 days, 8:49, 5 users, load average: 5.61, 8.69, 10.34