Filter Sets: Compatible With???

I have a set of variable contrast filters I bought on eBay a few years ago, when I first got back into photography and darkroom work. They're pretty old, made by DuPont for use with Varilour and Varigam, two papers that haven't seen the light of day in almost forty years. They seem to work okay, and I never gave any more thought to it.

But then I read this line in a Freestyle catalog, describing Oriental Warmtone VC FB: "Compatible with Ilford Multigrade Filters."

What does that mean? Why would I need Ilford's filters to use their papers? What "incompatibilities" might my DuPont filters have with VC papers made by Ilford and others?

TIA!

Spectral transmission characteristics and density are two things which will affect your result. Ilford MG filters have density adjusted so that 2 basic exposure times cover the use of the complete range of contrasts.

It pretty much means it works with most multi-grade filters. Basically, all MG papers currently available works with Ilford filters. Because Ilford is a dominant player in B&W supply scene and because of market shift, it's filters are pretty much the industry standard now.

These things do fade and shift color sometimes. If you are serious about B&W printing, maybe you can pick up a box or two....