Speed: JOBO cpe2+

[Bruce Osgood]

My older CPE2 + has two speeds, 75 rpm and 0.

Many of the development techniques using drums recommend using the slowest speed you can muster (Pyrocat HD for example).

Since I cannot turn slower than 75 rpm without burning out the motor, I am wondering if there is a way to adjust time and/or temperature to simulate a slower turning speed and what would the optimum revolving speed be?

Any ideas?

 

[cmichael]

Hello Bruce,

I have a similar issue since I use a Jobo Duolab that does not have speed control. In my findings, the issue with Pyrocat rotation speed appears to be one of acutance and not excessive development of highlights and/or oxidation of the developer. Someone please correct me if this is not the case.

When I first tried Pyrocat HD, I developed 4x5 sheet in my modified Duolab and everything seemed OK to me at first. Made some test shots, dialed in my development times, made a few small prints and was confident enough to use it on some ‘important’ shots. The acutance issue became obvious when I used Pyrocat/Jobo on roll film. At first I thought some shots were just poorly focused or maybe had some vibration from wind, etc. But I kept noticing things were not quite right. I went back to my original tests and pulled out a loupe to look at them under a light table. Sure enough, they all had a slight blur to them. I just did not notice it when printing at small magnifications. Stupid me, I should have checked it earlier.

I have since switched to using standard inversion and semi-stand agitation methods and everything is tack sharp now.

Again, these were my unscientific findings. IIRC, the metol variant of Pyrocat is supposed to improve this issue with constant rotation. Although I now use Pyrocat-M, I have not tried it on the Jobo.

Regards,
Chad

 

[Jerzy]

You may try variac (variable transformer) to slow down rotations. I am using this with the Beseler base, normal speed is about 32 rpm (at 120 Volts), with variac I am able to slow down to about 16 rpm (at 77 Volts). I tried cheap light dimmer and it does not work, looses power rapidly. However I have no idea how variac setup will behave with CPE+.