Oh it's hella more than 4. The people I learned enamel from who didn't understand enamel said the more you fire it the more the colors wash out, but that's probably bullshit Thompson enamel which doesn't include all the wonderful cadmium and other toxic heavy metals. Last enamel project I did fired like 16 times?
But it's not a big deal. You fire up your kiln, get out your trivet, get the temp to exactly what it oughtta be and then slide it in there for two minutes and fifteen seconds and you pull it out. That part's pretty chill - it's the bendy little wires that are aggravating because you wanna get 'em exactly right and you have to bend them with tweezers and if they move while you're firing (if the glacier shifts, really) you're fukt and every imperfection you made while you were bending them becomes increasingly annoying with every subsequent firing.
My buddy with the real CNC machine called me up yesterday and said "what order do you want these parts in 'cuz you got a backlog. You're making progress by leaps and bounds and I don't wanna hold you up."
Nicest thing anyone has said to me in weeks.