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I've just collected from my 'firer' over a dozen pieces I've thrown, bisque fired then glaze fired (all cone 5/6). Heartbreak ... every glaze has washed-out/faded so much that there's hardly ANY colour on the pieces; the exception being the few pieces i underglazed before applying the (over-)glaze. It seems almost certain that the earthenware clay I'm using will 'devour' any glaze i apply unless i apply an underglaze first!!

Any thoughts? ... i certainly hope i don't have to buy shares in an underglaze manufacturer in order to deal with this!?!?!?!

 

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Sounds like either they are over-fired, or the glazes are reacting with other glazes.  I have two commercial glazes (one red one orange) that state "do not fire with copper glazes".  I have rarely got any colour out of them eve when firing with no other glazes.

What glazes are you using?

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I'm using Cesco glazes (and Australian under-glazes). I don't believe it has anything to do with firing temps or other agents in the kiln because if i under-glaze first, pieces come out of the kiln with wonderful colouaration. It's when i don't first under-glaze that work comes out extremely pale and almost colourless.

I never had these problems when using an identically described mid-fire clay before i moved to my current address and started using, again, another mid-fire clay.

So i'm fairly confident it has nothing to do with the kiln, firing temp and (presumably) the glazes because, as i keep saying, if i underglaze first the results are delightful. Beats me ...

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Sorry Pres, i can't photograph them as they're all wrapped up as Xmas gifts. However, the thing you'd spot immediately is that they are very pale yet with excellent surfaces. Imagine: what was meant to be 'Burgundy' has come out an insipid cream with a very  occasional pinkish streak. 

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@GregP think there is a bit of terminology mixup going on here. If you are firing to midrange ie cone 5/6 and using anything (from white to) red / orange/ brown coloured clay then that would be stoneware, even if it’s the colour of terracotta earthenware. Earthenware is typically fired in the 06 - 04 sort of range.

Re underglaze, if you want to keep getting that look you can coat pots with a layer of white slip instead of underglaze, far less expensive. Was your former clay the same colour as your new one?  If new clay is much darker in colour it would explain the glazes looking different.

Edited by Min
clarity

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Further, the clay i used and what i'm using now are both the same colour (ie off white/light grey). I'm doubtful that the temp is the problem(?!?!?!?) as the glaze finishes perfectly, just much 'faded'.

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Are they these glazes? Did you thoroughly mix them up before using? Looks like stains used for the colourants of those glazes, stains are heavy and tend to sink to the bottom of a glaze. What colour underglazes did you use? Wondering if they intensified the colours of the glazes?

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Yes, almost all of my glazes are the Cescos you've attached. The undergalzes i used were white, yellow, pink, green, blue, black, red and perhaps another colour or two. I believe i mixed them well but i might just reopen the jars and see if in fact i did. But i don't understand what you mean by "Looks like stains used for the colourants of those glazes"(?). The use of undergalze did more than simply 'intensify' the glazes; they made them colour as they were meant to be by reference to the Cesco sample sheet you referenced.

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My thoughts are the glazes were not mixed well enough, stains in the glazes tend to sink which would account for bleached out colours.  I don't find underglaze settle out.

Edited by Min

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Min, I think you may have hit the nail just where it hurts. The underglazes i used are quite 'thin'; indeed, most of them didn't need thinning before application whereas the glazes are all new (in pots) and appreciably thicker than the underglazes. When i get the chance i'll 'dig' down into the glaze pots to see how intense the colours are 'down there': i gave them a good shake before opening but i fear that was not good enough. Cheers for now ... 

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If the glazes are "transparent" then yes they will "fade" when placed on a non white body, which you are using.

I'm guessing that they are fired to the correct temperature?

When placed over underglaze, then the colour WILL be truer to the chart, grey body not showing through.

White slip made from e.g. Walkers 103 , porcelaineous, white when fired to temp you're going to, is much cheaper to apply and works well bringing colours up to where you want. You can use whatever clay fires white at temp you're going to, test to see it fits.

Make a slip with  a few drops of sodium silicate to lessen the amount of water required to make it the right consistencey thus avoiding cracking due to too much shrinking,, apply it at trimming  stage of leather hard . If using only on outside, dampen the other surfaces too, to even the moisture, then underglaze colours and your well stirred glazes should pop.

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Thanks for that Babs. No, the glazes were not "transparent" nor opalescent and my clay comes out of bisque firing almost perfectly white.. Yes, the pieces were fired at the correct temp; cf magnificent finish (not colour) on the glazes. And many thanks for your advice.

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