Tuesday, 18 June 2013

A warning about sharp sand

Here is the lidded container after a bisc firing yesterday.. there are some nice, natural cracks developing in the surface:

I will have to wait and see if the texture holds together okay. I had to discard several pieces last week because there were some tiny fragments of plaster under the surface which erupted, many days after the bisque firing. I am fairly sure this was caused by "sharp sand" mixed into the clay slip. Sharp sand is very coarse and gritty...little did I know that it was contaminated with plaster, and plaster in clay = nightmare!

Today I also tried to stir up some high-feldspar shino glaze which had settled into a rock-hard lump at the bottom of a bucket. Instead of scraping away at the surface with a metal spoon for ages (and cursing a lot) as I've done in the past, I worked a finger down the side of the bucket and prised large chunks of glaze off the bottom. Then the lumps could be gently squashed between the fingers and dissolved quite easily. Once I got it moving I added a little epsom salts (magnesium sulfate) to flocculate the glaze.

It's been a lovely warm day, really feels like summer at last and perfect weather for glazing pots. Hoping to get the electric kiln loaded and do a glaze firing towards the end of this week.


  1. Oh, shame. I didn't know that plaster comes up long after firing. : O I wonder why. Summer finally came! : )

    1. Yes, sometimes weeks afterwards with bisced work.I am guessing it's something to do with absorbing moisture and expanding. It's very hot today, but rain predicted at the weekend for Earth and Fire. :(