Grain difference same scene & processing, FP4, HP5 sheet

I took some shots with my 'Hackaroid' 4x5 using FP4 and HP5. I processed 2 sheets of FP4 and one of HP5 all together in a Jobo tank, using rotary with D76 1+1. I was surprised to see grain differences between the 3 sheets with HP5 presenting the smoother result and quite a difference between the two FP4 sheets, with FP4-1 quite coarser than FP4-2. The samples are of roughly the same sky area. What could account for this?

My previous experience using HP5 in 120 size was that I got a grain style similar to the larger grained FP4 sample here. At that time I then switched to using Atomal A49 which reduced the grain, producing similar results to the HP5 sample here.

As an aside, I've just processed a sheet of HP5 rated at 1600 using a home made version of Microphen, a formula for ID68 I think I found somewhere here and the result is amazing, quite contrasty but less grain than the 400 sample.

You need to print it to discern what is actually going on. HP5 has much bigger grain than FP4, apples to apples (current "+" versions of each product). But with certain developers HP5 blends the grain clusters more smoothly. And a lot depends on how much you enlarge it, the contrast etc. A number of us like the "watercolor grain" effect of HP5 in staining pyro developers. "Pushing" it is really just lopping off the lower
zones by underexposure and making up the density difference by overdeveloping what is left behind - one of the numerous interesting things you can try with this particular film.

i agree you gotta print 'em to start...

i no longer have a jobo processor... is it possible that there is some sort of "mechanical issue" with it? or maybe, not enough/uneven solution?

very interesting...