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  1. Glaze/Undeglaze Problem

    Thanks everyone for such helpful replies . I am taking on board all the suggestions and am going to incorporate them into a thorough set of tests to see if it will help me pinpoint exactly what I need to change. I'm guessing it may be a combination of factors, but hopefully by trying all these things out I will find a way of working with the underglazes that will be more consistent and reliable. Thanks again for all your input .
  2. Glaze/Undeglaze Problem

    Thanks Chris. I will try this, as I think there is certainly an element of this oil/resistance factor going on. I'm not sure whether it's the whole problem or part of it, but is certainly worth taking some extra measures to eliminate the effects of this and those are good suggestions. I quite like the painterly effect of underglazes and so tend to use them as fluidly as possible rather than in blocking colour, which is some of the reason for the uneven application. Having said that, I have noticed that there are some particular colours where the powder is more resistant to mixing well, and this does affect the level of control over their application. I'm not sure whether this is playing a part in this particular problem as the underglaze has been applied in this way all over and yet the problem is just in specific areas, though I will bear it in mind as I do some more tests. Thanks again
  3. Glaze/Undeglaze Problem

    Thanks for replying TJR Yes, the colour is all from underglaze onto white earthenware, covered with a clear glaze. And yep, definitely underglazes and not slips - I buy them in powdered form and mix them with a universal medium (they can be mixed with water, but the medium is meant to give better results. I've tried both ways and it's definitely better with the medium ) to create a liquid that can be painted on. I will give your idea a try. When I first started using underglazes I did try painting them onto greenware, but they didn't seem to fix evenly at bisque temperature and I then found they were moving around in some places as I applied glaze. However, that was when I was also trying to use them by mixing with water, so it's definitely worth another go. It's odd though, that this is only happening on areas where there is either the sharp curve of a handle or on lips, edges where there is a sharp corner. On the rest of the piece it is fine. Don't worry about complicated - it makes me go away and learn . Every day I realise how much more there is to understand if I want to be able to solve my own problems! You've been very helpful - thank you .
  4. Glaze/Undeglaze Problem

    Thanks for replying Chris I've used no wax resist on these pieces at all, so the more I think about it, the more I'm starting to think that it could be this issue of oils from my fingers. Though I am amazed that it has had such an effect!! The clay's firing range is 1060C to 1150C so it's well within the maturing range by the time it's gone through all the processes. We think the rough surface on the exposed clay has been caused by the way the underglaze and glaze has come away as where there are unglazed bases everything is as you would expect.
  5. Hi folks, I'm new to this forum as a member but have been signed up via Facebook for some time and have found the forums useful for finding all sorts of information. I thought I'd better say hello as I'm now looking for help!! So, here's the problem..... I've just taken some pieces out of the kiln after a glaze firing. The pieces are made from earthenware clay with an underglaze decoration that had been applied to bisque and fired on prior to the application of the glaze. After the glaze firing areas of decoration have chipped away taking glaze and underglaze off to leave bare clay. Please see the pictures for examples. The damage seems to have occurred mainly on handles and edges. There were also some flat pieces in the kiln where the flat surface has fired with no problem but there are odd areas of chipping round some of the edges. I have used this type of decoration in the past and there have occasionally been issues with small areas of glaze crawling to leave bare underglaze but the underglaze has never come away like this. Other pieces in this firing that did not have an underglaze decoration have fired perfectly, as have some small dishes that were painted with underglaze on the upper surface only so I don't think it's a glaze fit issue. It seems to be related to the underglaze where it is on areas such as handles and tight edges in some way, I'm just not sure how The underglazes I use are powdered which I mix with a medium to apply to bisque clay. I bisque to 1000C and fire the underglazes on to 1120C. I had tried firing on underglazes to a bisque temperature previously but found it didn't fix them sufficiently. The glaze is brush on and was fired to the top middle of it's range at 1120C with decent temperature ramps on either side and a 45 minute soak at the top. This usually gives reliable results. One theory we have come up with is that as I've been handling the pieces while painting on the underglaze my skin has left oils on the clay which may have interfered with the underglaze bonding to the clay. Is it possible that this could create such drastic damage? If not then what could?? Any help and advice is most gratefully appreciated!!