I was looking forward to having some finished work. It turned out I needed to learn a valuable lesson in press moulding first.
Pinholes began to develop in the glaze even as I brushed the first coat. I tried to rub them over with my fingers but somehow they kept coming back. All the way through firing, re-glazing and re-firing as it turned out.
I thought at first it was an out gassing issue but close examination after the re-fire told a different story. These pinholes were literally ‘pin holes’ left from checking wall thickness.
The wine cups finished a few weeks ago were pressed and out of the mould as quickly as possible. The outer seams and surfaces were smoothed and compressed using silicone ribs while the porcelain was still malleable. Any pin holes were completely sealed and showed no evidence after firing.
This time around I let the pieces sit in the mould for a day. The surface was too firm to work with the silicone ribs in the same way as before. Instead there was a lot of scraping, tooling and spongeing. All little sanding after the bisque too. Unwittingly, I was exposing the pin holes instead of concealing them. A tough but important lesson.
From now on, a finer pin tool will be used to check the walls, inner surfaces will be worked until they are just right, forms will be removed from the mould within an hour and all finishing will be with the ribs. I know now what I need to do to achieve the quality I am after.
This was an important lesson but one that has left me with many seconds. I need a few days to think about whether or not I am going to finish these with the yellow and white gold rims, eyes and other details the way that I had planned.
I am considering a couple options to fill the pin holes. One involves making up a special paste and re-re-firing and the other using gap filling cyanoacrylate capped with fine black epoxy putty. The putty is sure fire, the paste not so much. I’ve ordered some of the putty but do not expect it to arrive for a couple weeks.
Firing off the last load as I write this. It’s anticlimactic though when you know the work will have the same issue.
While I consider the options, I am glazing some small vases that were bisque fired at this time last year. Exploring some new combinations with the polymer glazes. The ones I like best will be part of the furry garnitures once I get back to them in the new year.