Rob and I reviewed some of the pieces I had glazed prior to lockdown. There were the ongoing problems of pinholing and crawling in addition to the glazes being patchy and not turning out quite the colours I expected from the tests. Perhaps not too bad from a distance... But close up - no! Rob suggested some of the problems might stem from dust or oil from hands, and that I should give them a wash and brush up before glazing. I will also retest the bigger batches of glaze after I make them. For some colours, for instance the pale purple / lavender above very small differences in cobalt composition and thickness make a difference to colour. Position in the kiln may do too; I will have to make more notes. We also discussed a different surface treatment: applying white decorating slip to the freshly carved pieces rather than sponging down, in order to fill the micro holes created by movement of grog. It certainly creates a smoother surface. Even with quite this slip, seived through a 100 lawn mesh, the slip is difficult to get into all the holes, needing a little firm rebrushing. I have put on 2 layers and hope that when fired it is sufficiently smooth and even. I will have to check whether the holes have reappeared. This picture shows the difference made (from right to left) by one layer of slip applied with a firmish brush. The white decorating slip recipe I've used is 50 ball clay 50 china clay 10 flint which will create a whiter surface on the ES40, making the glaze colours brighter. I also emailed Valentines Clay regarding a slip recipe for this clay; Alan replied suggesting 75% ball clay 25% china clay I will try this if the 'fit' is poor on my pieces For those pieces already bisque fired Rob had advised that I should apply white engobe then refire. The results are on the next blog!
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AuthorI am indulging my passion for ceramics by undertaking studies for an MA at UCLAN Archives
August 2021
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