Finally here’s what I’ve found
www.silkscreensupplies.com sells after-market frames and supplies.
The emulsion they use is WBP Hybrid emulsion. It is a lovely color of red, but you must work under a yellow safe light, even when blowing the screen out. What I did was cut a piece of insulation and covered it with black plastic (or black fabric/felt.) Place that inside the screen, then weight it with books or bricks. Make it pretty heavy: the screen has to make a tight contact with the screen. (The Yudu people say 5 lbs and Ryan says 25 lbs. I used 4 big art books. But you get the idea.)
Save time and money and run an emulsion exposure test strip.
For a 110 mesh screen expose for 14 minutes (Yudu counts to 10 minutes so you will have to reset for 4 more minutes.) Then wash out, still working under a safe light.
I did quite a few experiments until I watched Ryan’s video on www.silkscreeningsupplies.com. WBP is very light sensitive, in my opinion.
TZ by Ulano (thanks to DeeDee Triplet for suggesting this emulsion), exposes in 3-1/2 minutes, easy blow out and reclaim screen.
Yudu will work with any size screen that will fit on the glass. Again, a tight contact is important. Make sure the transparencies are dense black, and add the black foam insert to fit the screen, and weight it.
I think the TZ by Ulano has my vote. It’s not so fussy and readily available.
I also think YUDU are out of production. Michael’s has some of the YUDU products on close out. You can sell/buy YUDU – just look online.