Cloudy Mixture and Sediment: Is This A Problem?

Snapshot · Sep 16, 2007

Hi All,

I mixed together a custom high definition film developer formula and I was using regular tap water instead of distilled water (I ran out of distilled water). It seems the sodium carbonate has combined with the dissolved minerals in the tap water to form a water precipitate, calcium carbonate most likely. As a result, the mixture become cloudy when stirred and when it settles, the mixture has a sediment layer at the body of the bottle.

My question is...

Will this (calcium carbonate) precipitate be significantly deleterious to film development?

I was considering carefully decanting what developer I can after it settles and then discarding the rest. I figure it would be a waste to discard the entire developer. Any thoughts?

gainer · Sep 16, 2007

It may be that enough carbonate was precipitated to change the pH of the working solution, but not likely if the water is potable. If you want to use tap water, try adding a little EDTA before dissolving the developer chemicals. If you are compounding your own, sodium metaborate may provide enough pH and is not likely to precipitate calcium and/or magnesium.
Sodium carbonate and calcium hydroxide react to form sodium hydroxide which is very soluble and calcium carbonate (limestone) which as you have seen is very insoluble. Magnesium carbonate is also very insoluble. If anything, the pH should rise a little when you use hard water.

Snapshot · Sep 16, 2007

For EDTA, am I looking for...

EDTA Tetrasodium
EDTA Acid (Granules)
EDTA Di-Sodium Salt

Or are they all one in the same?

Photo Engineer · Sep 16, 2007

Use Disodium EDTA to maintain the pH at the proper value as much as possible, or the tetrasodium version. You can still add it and probably save the developer. It sometimes works.

Another fix is to estimate the amount of sediment (such as 1 or 1/2 gram) and then add that much extra sodium carbonate to the developer. Then you filter it. That should adjust the pH value back to where it should be if it has changed at all. Usually the tiny amount of precipitate will not harm the pH, but the gritty particles will harm film unless removed somehow.

Filtration alone almost always works, unless you use a cheap filter. Try a good, fine coffee filter.

PE

Snapshot · Sep 16, 2007

I estimate about 1 gram of precipitate for the developer. Most of it can be filtered out but there is some fine precipitate that would not likely be filtered. I'll try some EDTA tetrasodium and see if that helps.

Thank you Gainer and PE for your input.

gainer · Sep 16, 2007

Yes, it is more like a colloidal suspension than a precipitate, but eventually settles. I have not found it to do any harm, but might if you are contemplating stand development for long periods.

Photo Engineer · Sep 16, 2007

Actually, tiny particles of the solid material can be trapped in the gelatin and can then cause spots in the finished negative.

PE

Snapshot · Sep 17, 2007

If that is the case, it would seem that unless I can filter out everything, it would be better to discard the developer and start fresh with distilled water. I think this is a good example why one should use distilled water for formulas.

gainer · Sep 17, 2007

Demineralized may be cheaper than distilled and should be sufficient. If you have a dehumidifier or air conditioner, its condensation is usually good enough.
What can happen has not yet happened to me when I used my well water, which is quite hard. Hard water is good for the heart, so I do not want a water softener, but it would be nice for the washing machine. OTH, most detergents now have chelating agents to prevent soap scum.
There is no arguing with worry warts. I have them in my family. They think I'm just sloppy and will poison them all. There are times when I think "If only it were so."

Photo Engineer · Sep 17, 2007

I would not suggest using water from a dehumidifier or air conditioner. This water is effectively distilled, but does accumulate mold and bacteria as well as room dust and contaminants. We were warned not to suggest this due to the possible contaminants. So, if the container on the dehumidifier feels slimy or looks brown or green, don't use it, and suspect it in any case.

PE

gainer · Sep 17, 2007

My dehumidifier has a 2 gallon reservoir. It is pretty well covered from anything that does not come in from the cooling coils. I installed a drain for convenience so I wouldn't have to move the tank to drain it. The drain is not quite at the bottom of the tank, so there is some room for sediment. I clean it out every so often. I can tell when the water gets discolored or slimy. I thought of installing a fine filter between the cooling coil and the tank, but I have lost the Round Toit that one of my kids gave me.

Snapshot · Sep 17, 2007

Well, I bought distilled water to ensure no unwanted precipitate forms. Unfortunately, I don't have a dehumidifier so I am forced to shell out for water. However, at a $1.40 for a gallon, it's a small price to pay to consistency. Thanks again for your input gentlemen.

Cloudy Mixture and Sediment: Is This A Problem?

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