Reuse of developer

[xwhatsit]

Hello,

I've seen it written many places that reusing 1L of Microphen ten times is acceptable. Now, firstly there seemed to be some confusion whether or not this was one film at a time (10 films), or 10 films with two films at a time (5 reuses). Clearly this is for using Microphen as a stock solution, no dilution.

At any rate, how does this pan out when using the Paterson style tanks which take 300mL of solution for one roll of 35mm? Does this mean 1L of developer can be used for up to 30 rolls of film? Or does the 300mL quantity mean the developer is exhausted sooner, and you still only get 10 rolls out of it?

I take it one increases development times every time the developer is reused.

 

[Freakscene]

10 films per litre is the capacity, that doesn't change. If you develop one film at a time you develop then return the 300 mL of used developer to the stock solution, then get the next lot of developer from there. This is complicated slightly by the inherent oxidation rate of the developer increasing after you return the used developer to it. You may have to experiment to get your times right and you are unlikely get similar consistency as you would with fresh developer. I'm assuming you have your time, temperature and agitation well controlled (consistent).

Ilford explain most everything well here:
http://www.ilfordphoto.com/Webfiles/200621612182416.pdf
see "Reusing developer without replenishment".

Marty

 

[xwhatsit]

Ah, thank-you, I should've checked Ilford's website. It's an unusual concept for me, a company actually providing useful technical details about their products freely!

I think I understand the process much better now. Thanks for the info.