I was recently approached to see if I could make 100 little bowls to be used as canary nests. The bowl itself is simple, it is the dimensions that need to be pretty accurate. The bowl fits into a round wire hanger that sits under the rim of the bowl so that it can be hung in the bird cage with a round piece of what looks like felt, or something similar, to act as a liner for the nest. The hanger is a fixed size, so the bowls can't vary much in diameter. They also have a few holes punched into the bottom. Easy Peasy, right?
I have a fired bowl to use as a reference, but as it has already shrunk, I can't use it for accurate measurements, so instead I used calipers and eyeballed an additional 1/3" on either side of the bowl. I am using a plainsman terracotta and they provide excellent data on all of their clays regarding shrinkage rates and the clay I am using has an approximate shrinkage rate of 9% going from wet to fired (^04). I plunked 22 pounds on the wheel this past Saturday and threw 23 bowls off the hump. That took about 1 hour to do, give or take. I then threw another 23 bowls on Sunday from the remaining 22 pounds. So in 2 hours, I threw 46 bowls, it took another 10 or 15 minutes to thumb the bottoms and punch 3 holes at the bottom of each one. What I am really amazed with is how accurate I was throwing of the hump as I don't do a lot of this type of repeat ware, I usually wedge individual balls of clay for the piece unless it is lids and spouts. I throw those off the hump all the time. There were a few that were smaller and a few that were larger than the average, but that was mostly depth, the width did not vary much as I had the calipers to guide me. There is no way that I was going to wedge 100 1 lb balls of clay for this, the profit margin is pretty skinny, if present at all, so I needed to save time by not wedging and not trimming. The first 46 are drying now and I will soon know if my measurements were correct, fingers crossed.