How long with 55g of water last?

[pentaxuser]

Folks, Ilford recommends washing RC papers for 120 seconds. That is in slowly running water.

Matt, your sentence sounds like it might be the key to the whole thread but a quick check of the posts seems to reveal that this has only been stated twice. The other time was by someone who is a Pentax user but not Pentax Pete

pentaxuser

 

[Ian Grant]

Missed this post at the time. Yesyerday U canned a WWII Kodak Research article or more precisely a precis of Communication No 910, G.T.Eaton and J.I. Crabtree of Kodak Research Laboratories, Rochester. This was first published in "american Photography! June 1943 and the BJP Sept 10th 1943.

Communication No 910 is the research into the use of sea water to wash films and paper. Essentailly hypo is removed much faster with a sea water wash but the final wash/rinses need to be fresh water.

Ian

 

[bernard_L]

You'll make a more efficient use of a limited quantity of water if you divide it into (a) rough rinse; (b) final rinse. A numerical example: suppose you have do dilute one (1) unit of hypo and have 200 units of water. If you use the 200 units of water straight away, you can achieve (at best) a final concentration of 1/200 of the unwanted hypo. If you first do a rough rinse in 100 units of water, you achieve 1/100; and then, move to the final rinse, you divide the concentration by another factor of 100, reaching 1/10000. Assumptions, simplifications, but you get the idea.
After some time the final water gets demoted to rough rinse, and replaced by new water.

 

[Ian Grant]

I should have added the Communication No 910 states that the research conclusded sea water washes films and papers twice as fast as tap water in terms of hypo removal, then films or paper need a short wash to remove the salts in the sea water.

So if you want to conserve fresh water use sea water first, or lake/river water, I'd suggest it's filtered first.

Ian

 

[wiltw]

After the use of Hypo Clearing Agent, wash times are 20-25% of what they are without using it.