Stan Klimek mentions waxing Pt/Pd prints with Gamblin Cold Wax Medium. I haven't waxed any pt/pd but I have tried it on argyrotypes and it looks beautiful. There's a small section on waxing by Klimek in the last appendix in Arentz's book.
I should add that the effect is very subtle, like a duller semi-matte seen on gelatin silver finishes, but does add a subtle richness
Anybody Hydrocote Polyshield Gloss wood finish? (Non yellowing polyurethane especially designated for exterior use.) IME it will give you about 1 stop (log 0.3 - 0.4) dmax increase and slightly more open shadows... But look is very different; not everyone's cup of tea!
Okay, I spent 26.00 for a 200ml can of R. wax and took one of my Point Lobos prints that is Pt/Pl and wax the hell out of it. I got about nothing as making the blacks deeper. For all the work and cost it really isn't worth it. I did try it on a OHP negative and it did protect it but again not worth it. this only pertains to using Pt/Pl printing on Arch. paper.
PS my wood turning friend loved the present I gave him though.
"Capturing an image is only one step of the long chain of events to create a beautiful Photograph” See my updated website: mandersenphotography.com
I've made wax from bleached beeswax and damar resin, you can get both from Talas. This is an "old time" concoction and it makes a big difference on a vellum print.
It makes it too silver print like for my tastes, but its interesting option for some work.