Processors and algae

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I've just got myself a Paterson Autotherm which is a similar but simpler design principle to a Jobo rotary processor i.e it rotates the print drum in a thermostaticlly controlled water bath. Its fill volume is about 13L (3 gallons) so I prefer not to fill it too often . However after about 3 days use I can feel the bottles getting a little slimy to the touch and there is a very slight bloom to the water surface.
Anyone found a way to prevent this ? I suppose a pelasantly warm temperature of 25 deg C/ 75 F (which is what I use) is ideal for growth of algae.

Cheers CJB

 

[Ian Grant]

It's probably best to change the water every session.

With a Nova tank you can add a little Sodium Hypochlorite to the water bath, but because the print tank is immersed in the water with the Paterson you run the risk of contamination, and this is another reason for using fresh water each session.

Ian

 

[Ryuji]

An effective and inexpensive biocide that is photographically inert is sodium salt of 2-phenylphenol. It's not the safest compound on the earth, but it is relatively nontoxic to mammals if compared among biocides.

More info:
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Household bleach or sodium hypochlorite is not desirable where it may come in contact with photographic materials. It is also not the best thing to allow a long-term contact with plastic materials.

Another common trick for algae suppression is to use a borate. (Borax, tetraborate, metaborate, kodalk and boric acid are all toxic to plant, but this is an application of this fact.) This is common for pool water, where about 20ppm of borate is used in combination with chlorine. For your application, 1.0g per gallon of sodium metaborate (Kodalk) is probably a good starting point, most preferably in combination with a few flakes of sodium o-phenolphanolate mentioned above.

 

[Roger Hicks]

I've just got myself a Paterson Autotherm which is a similar but simpler design principle to a Jobo rotary processor i.e it rotates the print drum in a thermostaticlly controlled water bath. Its fill volume is about 13L (3 gallons) so I prefer not to fill it too often . However after about 3 days use I can feel the bottles getting a little slimy to the touch and there is a very slight bloom to the water surface.
Anyone found a way to prevent this ? I suppose a pelasantly warm temperature of 25 deg C/ 75 F (which is what I use) is ideal for growth of algae.

Cheers CJB

Fizzy sterilizing tabs sold for sterilizing baby bottles are what I use. They extend the life of the bath before sliming by a factor of 10 or more. Chuck two or three in; you don't need a high concentration.

Cheers,

R.