Bergger BPFB-18 Film and Contrast Filters

I am trying to make enlarged copy negs from 35mm using a Leitz enlarger and Bergger BPFB-18 copy film. I enlarge the original neg to make an 8x10 positive and then contact print that to make a negative, which is then contact printed onto POP paper.

Here's my question -- this film is "blue sensitive." Is it possible using color filters to alter the contrast of the positives and negatives? I have tried using yellow and magenta filters, but they seem to have little effect. Does anyone have experience with this? I would like to change the overall contrast of the 35mm neg to make it more suitable for the POP prints (more or sometimes less contrast), but cannot figure out if there is a way to do this with the color filters.

Any suggestions will be much appreciated -- thanks!

The best way to modify contrast is the developer you use.
I enlarged 6x7 negatives to 11x14" for an exhibition using that BPFB-18 film.
I developed with Rollo Pyro 2+1+50 in dishes for 12 to 15 minutes constant agitation and I made contact palladium prints very easily.
You can see the results here:
Dead Link Removed

There were multicontrast copy films some years ago, I still have a box of an AGFA version. But you get a far greater available range through development! In one case an in-camera 18x24cm negative, developed in Ansco 130 (paper developer) needed a real boost in contrast. I bleached it and redeveloped in a single-use mix of one teaspoon pyrogallol and two teaspoons sodium hudroxide in one liter water. Instant contrast! It now has the full POP range of 11 stops, while still being printable on VC paper.

I have used this for enlarged negatives and relied on test strips and development times. After all, with the use of filters for printing, it is the paper that is sensitive to the colour combinations.

Thanks guys! I am using Zone VI PRINT developer on the film and am quite pleased with the results. Taking your advice, I diluted the developer 1:4 instead of the usual 1:3 and the density range dropped down to just where I need it. Filtration does not seem to have any effect on contrast, but development handles it very well.

Thanks for the help, APUGgers! ) You're the best!