Quote Originally Posted by Mike Lyons
Hi, now that Agfa have gone belly up, have swapped to Tetenal C-41 chems. Problem- their time for the blix is 4mins, my Jobo time is set and not reprogramable at 8mins. I realise the blix stage is supposed to go to completion, but will there be an adverse effect in doubling the recommended time? Tetenal instructions say a 50% increase is O.K. but what about a 100% increase. Anyones comments would be appreciated before I commit film to chemicals.
I too use the Tetenal Colortec C-41 and have just had a look at the instructions. The blix times go from 4 mins for 1-4 films to 15 mins for 13-16 films. So there has to be quite a spectrum of useable times. There are also times for processing at 86 degrees F if 100 degrees F produces uneven results. At 86 degrees F minimum blix times is 6 mins and rises to 8 mins for 5-8 films. There's also a section on deviations in results. Nowhere there does it mention a problem caused by overblixing. All of this suggests to me that extending blix times to 8 mins isn't critical. Indeed it is essential if you use the same blix for a greater number of films.

OK at worst, using the processing times for 86 degrees F the first 4 films will be overblixed to the tune of 33%( 8mins as opposedto 6 mins) but thereafter the blix will be spot-on. You're right that it says the blixing times can be increased by 50% but on the above basis the increase is only 33% so well within the extension.

I can't say there won't be a problem at 8 mins with the first 4 films as I have never tried but based on the instructions I'd be surprised.

As PE says contact with Tetenal or a knowledgeable user of Tetenal may be the belt and braces solution but based on the above info issued by Tetenal, I'd certainly have no worries if it were me.