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#21 Chris Campbell

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Posted 18 December 2013 - 10:27 PM

I have had more problems with clear glazes than with underglazes, slips and stains. Mostly potters think clear glazes are rather neutral when in fact, they cause a lot of problems. I show my students a wide tile of a colored clay pattern with various clear glazes over ... You can easily see discoloration, running and blurring with some of them. I use the Amaco clear and the zinc free clear whenever I need to use a glaze ... But I tend to avoid glazing since I don't do much functional work.

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#22 Celia UK

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Posted 19 December 2013 - 03:46 AM

Thanks everyone! Babs - oxide on greenware is something I hadn't tried - will have a go at that. Neil - it never even occurred to me that oxides might require different temperatures - something else for me to think about.

I do test with small pieces and tiles, but was trying to cut down some of the variables. As always I left the decoration of a few gift pieces rather close to Christmas - and hadn't ascertained a consistently reliable approach to the oxide application.

In case anyone has anything more to input - I'm using smooth white earthenware, and copper oxide & carbonate are my favourite oxides. HOW I apply the glaze is another matter! Given the pierced holes, I've found dipping and pouring quite problematic - drips and runs. I have a manual spray gun but it takes a lot of pumping and really needs a third hand to keep my whirler spinning! But I think this is probably still the best option for a smooth covering - and it's less likely to cause the oxide to run. I'll try to attach a picture of one bisqued bowl which I have airbrushed with copper carbonate (waiting for a decision on whether to do a 2nd bisque before glazing!) so you can see what I'm on about and another finished piece with the effect I'm after (I made this way back and can't remember how I went about it!)
.Attached File  image.jpg   89.7KB   2 downloads No idea why my photos turn round when attached - perhaps it's an ipad thing!Attached File  image.jpg   95.82KB   1 downloads

#23 Babs

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Posted 19 December 2013 - 06:07 AM

Nice bowls!

Another plus for applying to greenware is  that you can scratch and carve designs into your pot after applying the oxide wash. Sgraffitto i think is the technical name.

Small areas you could lay the glaze on by brush.



#24 Marcia Selsor

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Posted 19 December 2013 - 08:53 AM

check out some of the slip trailing videos on CAD. One shows how to make slip trailers with mylar wrapping paper.

I tried this and it worked really well.I had some wrapping paper scraps and used those. I sometimes get a blurp from the slip trailed needle nose applicators. Sometimes I add a glycol solution to avoid this but I haven't had any glycol around for a while. I use oxides mixed in my porcelain slip.

 

Marcia



#25 neilestrick

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Posted 19 December 2013 - 09:34 AM

Norm, there are several problems with their underglaze 'study':

 

1. With the exception of Coyote, the underglazes they were using were not rated for cone 6. They were all rated for cone 04, so all of them were being fired well above their recommended firing range. Amaco fully admits that their Velvets will change color. They even put out a chart showing the changes!

 

2. They were using a cone 10 clay but only firing it to cone 6. So that could exacerbate any problems they were having with their clear glaze.

 

3. They were using commercial clear glazes, so they did nothing to try and fix the glaze problems they were having. No one glaze is going to work on top of all underglazes.

 

4. They mention nothing about flaking. They say blistering, fading, or changing colors. Blistering of the clear glaze is caused by the underglazes being overfired, which they clearly were, or a poor matchup of clear glaze to underglaze. Fading and changing colors is also caused by overfiring, as the colorants they are using are not specifically formulated for cone 6. It would also be nice for them to specify which brands suffered from blistering, and which suffered from color changes.

 

I'm not sure where you're getting your data about the underglazes flaking off. If it's from personal experience, I understand. But there's nothing in that report to back it up. In my studio we have used commercial underglazes on more than 10 different clay bodies, including porcelain, for the last 10 years, and they have never once flaked off. We apply them to wet clay, leather hard clay, bone dry clay and bisque. They flux out plenty, and they adhere just fine. The Amaco Velvets MSDS form even lists sodium borosilicate frit as an ingredient. So yes, they are fluxed. This is what causes the blistering with some clear glazes. If they were just kaolin, the blistering problem wouldn't happen.


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#26 Chris Campbell

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Posted 19 December 2013 - 11:38 AM

Thanks for posting this Neil and for taking the time to read the study.
I have never had problems with Amaco commercial underglazes and I definitely push them past their recommended uses!
I also have several test tiles showing all of the underglazes I commonly use fired at 06 and 6, glazed and plain. I recommend this to all.

Chris Campbell
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#27 Pugaboo

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Posted 19 December 2013 - 09:05 PM

I too use Amaco underglazes and am able to do an amazing amount of detail work with them. Now that I am more experienced I can do the color shifts in my head while I am painting to be able to know if this color that looks purple in the jar is actually dark blue. Most of the colors are pretty close though I have found the colors when dry but unfixed tend to be quite pale compared to the colors after firing and they look even better after clear glaze firing. I have not had many issues with them, and most issues I did have were due to my own learning how to use them. Now that I am more experienced I can pretty much do what I want with them and am working on painting portraits and detailed scenes on pottery currently. I use the Amaco zinc free clear over the underglazes. I have had some color shift issues with them when I used a different brand of clear. All in all I would recommend the Amaco underglazes to anyone looking to paint on pottery. I should note when I state Amaco underglazes I mean their LUGs not their velvets which so far of the ones I have tried I don't care for the surface and how it binds to the clay once dry. I like to paint, scratch, carve on anything from leather hard to bone dry (with a respirator) and I have found the velvets seem to sheer off in sections when carved through whereas I do not have this issue with any of the Amaco LUG underglazes. Others may love the velvets and dislike the LUGs.

I should also note that I really like the Lakeside pottery website and they have a lot of good information out there. If you haven't had a chance to check out their site do so its a great resource.

Oh! Just like Chris one of the first things I did was make color tiles with the underglazes which I keep hanging next to my drawing table. I did all the LUG line colors and did 1 stroke, 2 stroke, 3 stroke chips as well as each number of strokes glazed and un glazed. I learned a lot doing those color palettes and it's very useful to have them where I can glance at them while working.

Terry
The world is but a canvas to the imagination - Henry David Thoreau

#28 neilestrick

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Posted 19 December 2013 - 09:15 PM

We use Speedball underglazes in my studio. They are much less expensive than the other brands, and hold up well at cone 6. They typically come very thick in the bottle, so you have to thin them down, giving you even more bang for your buck. Every color is under $12 a pint, and many are $7-9 a pint. And if you get on the Clay-King.com email list, once or twice a year they sell them 1/2 price. The only color we have any issue with is the red. It tends to flux out more than the others, and can cause some bubbling of the clear glaze if it is applied too thick. Fixing that clear to work with the red is on my to-do list!


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#29 Pugaboo

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Posted 19 December 2013 - 10:06 PM

Neil,

Good to know! Next time they have that sale I might just have to buy a few bottles to play with.

Terry
The world is but a canvas to the imagination - Henry David Thoreau

#30 neilestrick

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Posted 20 December 2013 - 03:52 PM

Thanks, Norm. Even on its own, that red tends to melt out a bit more, almost starts to gloss out a bit. I'll have to give the Coyote a try.


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#31 TJR

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Posted 21 December 2013 - 05:04 PM

 

Ruth;

I paint on glazes all the time. In fact, all of my work is banded and  brush decorated. I use bamboo brushes that hold a lot of liquid. I paint oxides on bisque ware that has an unfired glaze on it. I glaze my pots, then let them sit for a day, then decorate over the glaze. Over the glaze you get a sharper line quality,as compared to decorating and then applying the glaze over that. The oxides need to flow, so you need to add just the right amount of water. A good starting point would be iron oxide plus a little Albany slip/Alberta slip. Try some designs on newspaper first. Check out my gallery for images. I apologize. I really need to update them.

TJR.

Great pots TJR!

Why do you add the Albany slip? To suspend  the oxide? Or to make  the oxide more Painterly?

 Benzine, I use oxides and underglazes on my glaze Both seem to work ok except one or two Blue underglazes which do not have the same melt as others. To these I add a bit of the Frit present in the underlying glaze, ot even someof the glaze itself and that seems to do the trick.

 

Ruth;

The Albany gives the iron a bit of dry strength. Otherwise it is just powder sitting on the rim. It also helps the iron to not settle like a rock before you brush it on. I always give it a stir with the brush before I paint-every single pot.

TJR.



#32 Babs

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Posted 21 December 2013 - 05:07 PM

 

 

Ruth;

I paint on glazes all the time. In fact, all of my work is banded and  brush decorated. I use bamboo brushes that hold a lot of liquid. I paint oxides on bisque ware that has an unfired glaze on it. I glaze my pots, then let them sit for a day, then decorate over the glaze. Over the glaze you get a sharper line quality,as compared to decorating and then applying the glaze over that. The oxides need to flow, so you need to add just the right amount of water. A good starting point would be iron oxide plus a little Albany slip/Alberta slip. Try some designs on newspaper first. Check out my gallery for images. I apologize. I really need to update them.

TJR.

Great pots TJR!

Why do you add the Albany slip? To suspend  the oxide? Or to make  the oxide more Painterly?

 Benzine, I use oxides and underglazes on my glaze Both seem to work ok except one or two Blue underglazes which do not have the same melt as others. To these I add a bit of the Frit present in the underlying glaze, ot even someof the glaze itself and that seems to do the trick.

 

Ruth;

The Albany gives the iron a bit of dry strength. Otherwise it is just powder sitting on the rim. It also helps the iron to not settle like a rock before you brush it on. I always give it a stir with the brush before I paint-every single pot.

TJR.

 

Thanks TJR I actually asked the question re. use of Albany slip, a rarer commodity these days, so can anyone suggest a substitute that will melt with the iron?



#33 neilestrick

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Posted 21 December 2013 - 09:36 PM

Redart would served the same purpose as Albany.
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#34 MikeFaul

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Posted 22 December 2013 - 06:52 AM

Babs/Neil - while you're on and before I get to bed ( it's 11pm in the UK) - quick response if possible. Can I fire my already bisqued pieces which have an oxide wash in places, to fix the oxide before glazing. As this will be 3 firings in total, and trying to keep costs down, how low could the 2nd firing be?

I fired some tests of sprigs we finished with a rutile wash over Amaco Velour Black underglaze, diluted to form a wash of sorts. We're trying to create the look of embossed distressed leather. Both are in a ^6 glaze firing, which we'll unload on Monday morning. The sprig is on the exterior of a cup, not a food bearing surface. We've fixed these two separately at ^6 (on bisque), and in bisque (on greenware) at ^06, ^05, and ^04, without issue.

I thinned the underglaze with 2 parts water to one part glaze (approximate), I wanted it to run around in all the detail crevices of the texture. I then sponged it off the ridges and high points. We diluted the rutile wash a good bit, maybe 6 parts water to one part base wash. Then applied it over the underglaze. As the under glaze was not fixed it reactivated, and I used a brush to blur it into the rutile. The kiln should be down firing as I type this, so we'll know soon enough if it works.

We used a copper was previously with inconsistent color formation, especially in conjunction with the rutile wash.

[EDIT] I've also rebisque fired bisque ware to fix underglaze and washes without issue on subsequent glaze firings.

#35 MikeFaul

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Posted 22 December 2013 - 06:58 AM

Also, are there two different conversations on this thread? I feel like I'm reading in stereo. :-)

#36 bciskepottery

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Posted 22 December 2013 - 09:57 AM

Mike -- I think you'll find, from time to time (or more often), that discussions seem to wander a bit.  Not so much stereo, but . . . maybe Babel or the school cafeteria at lunchtime?  Not a bad thing.  Just a life on the bulletin board or whatever they call these things. 



#37 MikeFaul

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Posted 22 December 2013 - 10:05 AM

Mike -- I think you'll find, from time to time (or more often), that discussions seem to wander a bit.  Not so much stereo, but . . . maybe Babel or the school cafeteria at lunchtime?  Not a bad thing.  Just a life on the bulletin board or whatever they call these things.


Didn't think it was bad, more amusing and hard to follow... But, that's just me...

#38 TJR

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Posted 23 December 2013 - 10:43 AM

 

 

 

Ruth;

I paint on glazes all the time. In fact, all of my work is banded and  brush decorated. I use bamboo brushes that hold a lot of liquid. I paint oxides on bisque ware that has an unfired glaze on it. I glaze my pots, then let them sit for a day, then decorate over the glaze. Over the glaze you get a sharper line quality,as compared to decorating and then applying the glaze over that. The oxides need to flow, so you need to add just the right amount of water. A good starting point would be iron oxide plus a little Albany slip/Alberta slip. Try some designs on newspaper first. Check out my gallery for images. I apologize. I really need to update them.

TJR.

Great pots TJR!

Why do you add the Albany slip? To suspend  the oxide? Or to make  the oxide more Painterly?

 Benzine, I use oxides and underglazes on my glaze Both seem to work ok except one or two Blue underglazes which do not have the same melt as others. To these I add a bit of the Frit present in the underlying glaze, ot even someof the glaze itself and that seems to do the trick.

 

Ruth;

The Albany gives the iron a bit of dry strength. Otherwise it is just powder sitting on the rim. It also helps the iron to not settle like a rock before you brush it on. I always give it a stir with the brush before I paint-every single pot.

TJR.

 

Thanks TJR I actually asked the question re. use of Albany slip, a rarer commodity these days, so can anyone suggest a substitute that will melt with the iron?

 

Any dark clay. .I have to go to my studio to look, but any clay that will bring trace elements of iron along with it. Red Art,is good, but a bit coarse, ball clay even.

TJR.



#39 Shuli

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Posted 23 December 2013 - 02:58 PM

I've read that glycerin is supposed to make glazes more flowing.  That's something I want to try since I want to start combining my calligraphy with my ceramics and I don't want my brush to run out of glaze in the middle of a word!  Has anyone else tried glycerin?

 

Some artists use syringes from the medical industry for slip/glaze trailing as they get a very fine, controlled line with those.  It's an interesting idea but I'm not sure where I would get medical syringes.



#40 bciskepottery

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Posted 23 December 2013 - 03:10 PM

You might be able to find syringes at a farm co-op. 






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