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Thanks for the reply. I know I could do a test tile, I had a bowl that had some of the same characteristics where a white underglaze  over a blue underglaze all but disappered.  I quess my question is, when everything is molten do underglazes always tend to blend and level out? I was hoping somone with experiance using underglaze at mid-range temps cold save me some firing costs, plus I have been bisque and glaze loads for the last two days and my Wife wants to use the stove today. My process works fine at earthenware temps. I'm new to stoneware.

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i will ask a dumb question here.  why are you covering one color with another?  isn't that like painting a room one color and then painting it a second color?  what will you see?  the one on top.

 

 are you trying to make the blue a paler shade?  if so, mix the white with the blue until it looks the way you want it.  without a clue to your intention, we can't help.

 

 

try calling the underglaze manufacturer and asking their technical person this question.  assuming you are using the same brand name for each color.

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I was once asked to participate as a judge in an elementary school art contest. One class of 2nd graders had consistently better work than even some of the upper grades. After the contest I asked the teacher what she was doing with her class to produce such quality projects.

 

Her response was simple, "I don't really do anything differently, I just know when it's time to take it away."

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If the overlapping colors are underglaze, they should not mix.  Underglazes harden in the kiln, and flux a bit, so they bond to the clay body.  But it isn't enough that they become molten and flow/ blend like glazes.  

 

A clear over the top should also not effect an underglaze.  Though I've seen some say, to be safe you should use a zinc free clear.  In fact most, if not all of the underglazes I use, look better with a clear glaze over the top.  Some are intended to be used with a top coat of clear, and look rather bland without it.

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as the decoration developed I covered areas of  line and colour with other colours and lines. my concern is that when I open the kiln all the areas that I have covered over will appear again.  So for example...say I painted a house and a tree and the sky and the grass and then I didn't like the house and instead I want some flowers there so I paint the blue sky over the house and then flowers over the new patch of sky...Do underglazes melt at cone 6 in such a way that the finished piece will show evidence of the house still being there?   The underglazes are suppose to be opaque according to the label and this process of developing decoration works fine for me at low-range temps. I was just wondering if this is an commen beginners mistake 

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Underglazes tend to act more like paints.  By that I mean, you can layer them, without something showing through, in most cases, if applied thick enough.  However, I have tried to cover a really dark area, with a much lighter color, and had the dark color still show through.  So I guess it all depends on which colors were used on each layer.

 

I know this isn't a definitive answer.  But there are a lot of variables to consider.

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If the overlapping colors are underglaze, they should not mix.  Underglazes harden in the kiln, and flux a bit, so they bond to the clay body.  But it isn't enough that they become molten and flow/ blend like glazes.  

 

A clear over the top should also not effect an underglaze.  Though I've seen some say, to be safe you should use a zinc free clear.  In fact most, if not all of the underglazes I use, look better with a clear glaze over the top.  Some are intended to be used with a top coat of clear, and look rather bland without it.

I think That may be my issue, the clear glaze is revealing thin spots in the underglaze colour that the blandness of the dry underglaze is hiding... I just sprayed a mist of water over the decoration and found some problem spots...should be an easy fix. Thank you very much. 

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i will ask a dumb question here.  why are you covering one color with another?  isn't that like painting a room one color and then painting it a second color?  what will you see?  the one on top.

 

 are you trying to make the blue a paler shade?  if so, mix the white with the blue until it looks the way you want it.  without a clue to your intention, we can't help.

 

 

try calling the underglaze manufacturer and asking their technical person this question.  assuming you are using the same brand name for each color.

I looked in your Gallery Pics...I like your blue bowls particularly the sailboat under the moon. the simple tecknique of white line on blue has me thinking of them as dream imagery, nice work.

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I use Underglazes for painting on pots extensively. My experience is this...

 

A darker color like dark blue or black under a white or pale yellow will sometimes reappear after firing, and usually after it is glaze fired. It depends on how many layers of the lighter color you have over the dark.

 

The touchiest Amaco LUG colors by far are Dark Blue and Black. You need to use a Zince free clear and not heavily applied either as this can make the blues and blacks run. I think the black turning blue under a regular clear with zinc in it is because the black has Cobalt in it, just a guess but that's what I am leaning towards. Before I figured this out I ended up with some crying Pugs and nobody wants sad pugs.

 

If you use a bunch of heavily applied layers you will occasionally find after glazing that parts of these colors come away from the pot. This only happened when I first starting using the Underglazes and had not yet figured out how to do washy layers.

 

When using Underglazes you can blend the color right on the pot if you need to. What I mean is put a dark blue at the bottom of a pot and white at the top. You want a nice blended color from white to dark blue. So paint the bottom 1/2 dark blue and the top 1/2 white, let it dry now get a sponge wet it and buff the middle area together, you can achieve a really nice blended light to dark.

 

Underglazes don't run and won't bleed all over the place, they should stay where you put them.

 

Don't place underglaze pieces touching each other in the kiln, or at least not the dark blues or blacks or light against dark. I stacked some ornaments and the black lines from one put a halo of black on the ornament it was stacked on top of.

 

I hope this helps,

T

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So for example...say I painted a house and a tree and the sky and the grass and then I didn't like the house and instead I want some flowers there so I paint the blue sky over the house and then flowers over the new patch of sky...Do underglazes melt at cone 6 in such a way that the finished piece will show evidence of the house still being there?

One possibility to be careful of is compression from the clear glaze over too many layers of underglaze. A buildup of underglazes could create an uneven surface for the clear, causing it to be thinner on the high areas and not uniform in covering. If you are applying your underglaze on leatherhard/greenware, then think about removing a color/scene rather than just putting different colors over it. Some underglazes are more refractory than others -- they will show through -- especially those with cobalt in them.

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  • 2 weeks later...

Well I'm firing the kiln now... It's been seven hours and its at 1300F. This is the second go... I had to shut down and empty the kiln last night and re:re half the elements to clean out the grooves. It seemed to be causing the problem . now it's firing on all six coils...I sprayed on what I'm 80% sure is a zinc-free clear gloss on the interior of the bowl, and brushed on loads of an opaque green glaze called Joesphs green on the outside. ðŸ˜

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a so so result...I thank God for the successes, and the failures for what they teach me...I'll post pics to this thread soon. On a positive note... some issues with my kiln and the lack of proper cones meant it fired to cone 5 which it turns out is the perfect temp for Josphes Green which befor had always tended to burn out  and end up brown on my pots. I'm going to stick with cone5 for awhile

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Try carving through your layered underglazes to get a haloed effect, carve at an angle and the under layers will be slightly revealed. Can save on underglazes by usung latex resist to leave bare areas of clay  and peeling back to put in more colour, or resisting to put on more colour etc.

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Thanks for the reply. I know I could do a test tile, I had a bowl that had some of the same characteristics where a white underglaze  over a blue underglaze all but disappered.  I quess my question is, when everything is molten do underglazes always tend to blend and level out? I was hoping somone with experiance using underglaze at mid-range temps cold save me some firing costs, plus I have been bisque and glaze loads for the last two days and my Wife wants to use the stove today. My process works fine at earthenware temps. I'm new to stoneware.

I use a lot of underglazes. The biggest problem is zinc in the glaze you apply over the underglaze. It's essential to use a zinc-free clear. Other than that, the thickness of the underglazes plays a huge role in the final outcome. Too thin, and it will all but melt away... too thick, it sometimes leaves unpleasant lumps. Several coats of a good underglaze are the best way to go.

 

Some of my early pieces were ruined due to zinc in the clear I used. A beautiful grey dolphin with blue waves and white caps turned completely grey. I was devastated! Hours of sculpting were turned into a lousy piece!

 

I am a professional potter, and Community Manager for Big Ceramic Store blog. Feel free to reach out if you have any additional questions

mailto:bcscommunity@bigceramicstore.com

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