Friday, September 4, 2009

Clay Ruler

I have no idea where this idea came from… I’m assuming it was from an old copy of Ceramics Monthly, but I’ve been hard pressed to find it in my stack of old well thumbed copies.
It’s a very simple solution to a problem that pops up just often enough to be annoying.

This is the problem of the broken or misfit lid.

Like I said… annoying.
I generally limit my lids to just a few sizes to minimize the confusion but, for whatever reason, sometimes things don’t work out as planned.

A quick note for non-mudheads… Clay shrinks as it dries. With some types of clay it shrinks just a bit, (it’s still a fairly noticeable bit though), sometimes it’s quite a bit… and when work is fired in the kiln, it shrinks a lot! So pulling a measurement straight off a dried or fired piece of work can be problematic.

My fall back plan is the “Clay Ruler”.

This is a clay slab impressed with a ruler with its measurement markings raised. As the slab dries to bone-dry, it shrinks.

Now when I take a measurement with my calipers on the opening of a bone-dry green ware canister, I can get the measurement directly from my clay ruler.
Both are already shrunk so there is no guesswork math, I just note the measurement on my shrunken ruler and readjust my calipers using a regular ruler...
and throw a new lid.
(If you want to see my lid throwing process, click here...)

No problem… I throw a set of 3, bracketing a hair up and a hair down just to hedge my bets. Usually one of the three works out to be a perfect fit.
Now like I said, each type of clay body shrinks different amounts, so I’ve got different clay rulers for each clay body I use. I also have clay rulers that have been fired as well. A set of bisque fired rulers, and a set of rulers fired to cone 6 and cone 10.
As the old saying goes… He who dies with the most tools wins.


jimgottuso said...

that's a great idea! i never heard of it before and i've had that problem before and chose to overwhelm it by throwing 6 lids and hoping one fit correctly.

Sue Pariseau Pottery said...

You are always so informative. This is a great solution to every potters most annoying problem. Thanks!!

Morrigae said...

i agree abt racing to have the most tools b4 death over takes me. also, the clay ruler idea is great. your method of throwing a lid is interesting. looks like you threw from the hump? i need to ask the studio mgr abt that. it may make my lid throwing easier.