Originally Posted by Marc Carmen
Josh, I'm dying to try the durissimo. If it's a similar formula to Nero duro then it's a lead free iron sulfide black. Iron sulfide glass is not only naturally stiff but also incredibly brittle. Old glass container literature mentions that it is a cheap and easy way to black glass, if only it didn't make such an impractically brittle bottle.
Man, I have sooo many bubbly black filigrana in my student work haha.
It's not just stiff, it's CRAZY stiff! Definitely the stiffest glass I've ever played with and makes the white duro feel like enamel. I gather on the new black the instant it stops moving, which is literally walking from the gh to the furnace. If you lose the core heat you're toast. If you don't transfer it directly to a stick you're toast. Gathers needs to be done before the previous one fully sets up. Pulls need to be really hot with a faster walk than usual. If you don't have the black poking out of the end of the setup and quench before you stick to the post, you're toast. It's actually super fun to work with because it's so quirky. I've not had great luck keeping it jet black--I think it might have something to do with our gh running a bit rich (maybe Pete can explain what's up w/this). It's been going graphite grey on me--I'm going a few things to try to avoid this. I've been pulling it into cane, then bundling the cane and making murrine. I haven't used the murrine yet, but it looks excellent.
If you're into twisty cane, definitely try some of this stuff, it's wild and so much fun.