Jorge said:
You are talking about the Maxwell screen. The beatti uses a fresnel lens and a coated glass. Yes, the wax is the problem with those screens, you are not the only one who has complained about this.
Are you sure that you're not talking about the BosScreen, which uses a wax layer between to pieces of clear glass? I'm not aware that the Maxwell screen uses wax.
Beattie and Maxwell screens are a combination of a ground glass plus a fresnel lens, which evens out the light. Fresnels, though, are most effect with the specific focal length taking lens that they were designed for, and they give less good results with other focal length taking lenses. The BosScreen and the Satin Snow focusing screens don't have built in fresnels.
I've used high quality acid etched "ground" glass (Sinar), low quality groud glass (Toho), Linhof super screen (plastic with built in fresnel), BosScreen (wax), Beattie intenscreen plus (in my Rollei), and the Maxwell.
For 4x5 work with lenses from 110mm to 600mm my favorite is the Maxwell. It's bright, even, and easy to focus, although it should be for how much it costs. The Beattie works well in my Rollei TLR. I've heard the some people don't like'm, but it's an order of magnitude better than my original Rollei screen. I'm not a fan of the BosScreen, as I had focussing problems with mine. The linhof screen was ok, but it really needed the clear glass cover plate for rigidity, which I didn't have.
If I had to do it all over again, I'd try the Satin Snow screen first. It's sounds high quality and the price is right.