Couple of things:
- I am throwing with Laguna's B-mix 10 with sand. It's the first time I've used this body and I am quite delighted with its performance: centers easily, doesn't sag. I only bought one box, though, to test it out, so won't have enough clay to make many samples.
- I started using 12 lbs to make a 14" diameter, 5.5" high bowl, 0.5 inches thick in the wall. I was hooting for 16" diam, 6.5" high in the wet state. 12 lbs was not enough to do this; it fell short by a lot. 12 lbs was not even enough to make a similarly thick & tall bowl with a finished diameter of 12". Despite liking the shape, I wedged it up, because I didn't want to commit kiln space to a large piece that was destined to be not-quite-right.
- To get the bowl that will eventually be the 14" sink, I needed 18 lbs, which is the pot on the wheel in the photo above. It's surprisingly small for 18 lbs, but of course it had to be thick. I am not convinced this one is thick enough, so I will try again with 22 lbs.
- To that end: to save my poor median nerve (healthy, but I intend to keep it that way!) I center these large amounts in two equal chunks. When the first is on center, I scrape it dry with a metal rib, and then plop the second half on top. Much, much easier than trying to muscle the whole lot under control all at once.
- After my third attempt, it seems that 20 lbs will be the right amount to make the (eventual) 14" sink. Which means that the 16" sink - 19 inches, wet - will need to be around 28 lbs. My mind has jumped ahead to pricing: I don't think I can possibly get less than around $280 for these -- and that's the wholesale price. Which means someone, somewhere will need to be willing to spend almost $600 for a lavatory. I need to talk to my client before I get too far into this, in case that is a deal-breaker. The vessel sinks I have found online have retailed for between $90 and $1600; not sure what range he had in mind.