Sludge is that clay-like stuff that a mandrel is dipped in to keep the bead from sticking to the steel. There are a lot of different kinds made, and I have tried quite a few. Here's my run-down:
My favorite sludge so far is KRAG Mudd made by Kittrell-Riffkind Art Glass in Dallas, Texas. It's strong, dries in the flame, is nice and smooth when you dip, and leaves a lower residue than anything else I've tried. But yes, you do still have to ream the beads. And, though I've tried just using a pipe cleaner, it seems that a diamond reamer is still necessary to get ALL of the sludge out.
Right now I'm using Dip n' Go from Arrow Springs. I actually wanted to finally try the Foster Fire, but they were out (again). Dip n' Go is nice- it's strong, and it can be dried in the flame without weakening. It is not, however a really low residue sludge, and that is what I prefer.
Flame dry bead release from Ed Hoy- GARBAGE. That's where mine ended up. Because it's weak and hard to clean.
Air dry bead release from Ed Hoy- Pretty good. Strong, reasonable to clean, and it can actually be flame dried, so why bother with the other?
Alice's bead release- I don't like this. I find it VERY hard to remove the lumps, weak, and hard to clean out of the beads. But it is quite inexpensive, as you get it in powdered form and mix it yourself.
Frantz has decent bead release, though I haven't used it in years, so I can't tell you which I like best.
I'm still waiting to try the Foster Fire. I have heard good things, but can't say until I actually get a chance to try it out myself.
So why get all the sludge out, anyway? Some people don't, so why should you? Well, it's a powdery clay, and you're not really supposed to breathe it, so why make your customers do so? And how would it be if someone wore one of your bead necklaces into the shower, and it started weeping an icky grey slime all over them? I look at it as the last necessary touch to my bead-making, that shows how much I care.