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Applying clear glaze over underglaze


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#1 Pugaboo

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Posted 16 March 2013 - 10:44 PM

I have been doing some reading and it seems like applying clear glaze over underglaze when it is applied to bisque ware can be tricky. I didn't think to ask my teacher how to do this since I planned to apply all my underglazes before firing to bisque but well the best laid plans and all that.... So I have a piece that did not come out of the kiln after bisque firing quite as I had hoped so I have applied some additional underglazes hoping to "rescue" the piece. The problem I now have is how to apply the glaze without smearing these newly applied underglazes. The next session of classes does not start up again for a month and I'd rather not wait that long to ask what I am sure to those of you with more experience is a simple question. To get the BEST results do I pour, sponge, brush or dip the piece? It is a large platter so dipping might be hard but I could do it I guess in a plastic tub if I had to just not sure if I could reuse the extra glaze after doing something like that or not.

As you can tell I REALLY need help and really really appreciate your time for doing so.

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

#2 weeble

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Posted 16 March 2013 - 11:55 PM

Just send it back through the bisque firing, that will lock down the underglaze so you can put your glaze over. A couple rounds through the kiln shouldn't hurt anything. If that's not practical, you're just going to have to experiment to find out what works for you. Any time you glaze over something unfired, you could pick it up, and the wetter you get whats underneath, the worse it will be. I have one student who likes to futz with underglazes (the rest of us in the group use regular glaze) and I tell her to carefully sponge on the first layer of glaze. It works, but... eh, its so much easier if she just refires the second round of underglaze!
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#3 Benzine

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Posted 17 March 2013 - 09:23 AM

generally, I tell my students, that any underglazing, should be completed before the first firing. However, if they give me a compelling, aesthetically backed reason, I will allow them to both underglaze and then clear glaze back to back.
As we mainly use brush on glazes, I just tell the students to use very soft brush strokes, and go over the area quickly until it has had a chance to dry. Repeat until you have the required amount of clear coats.

It is definitely better to fire the underglaze, before applying the clear, but for my classroom, time and kiln space is alwys an issue, so sometimes that isn't an option.
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#4 Claypple

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Posted 17 March 2013 - 11:01 AM

Why make things so complicated? You can apply underglaze on either greenware or bisque. (check the directions on your underglaze bottle)
Let it dry before applying a clear glaze over it. Never had a problem.

#5 Pugaboo

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Posted 17 March 2013 - 11:35 AM

Time and kiln room is the issue I am encountering (along with many more newbie issues!). I think have fixed the underglaze color issues ( who knew light brown would be chocolate brown after firing?) and need to apply the clear glaze without smudging the dried underglaze, let that dry then drop it off at the teachers studio. He said I could do that between classes and he would fire it the next time he did a glaze firing. I do not currently own my own kiln but once I complete another class can join the group studio and have access to one then. I am using Amaco LUGs on little loafers and am going to order a gallon of Amacos zinc free clear glaze for the top glaze. I am trying to do detail work that I don't want moving around like regular glazes do in firing so I think, and correct me if I am wrong, my option for this is to use underglazes.

To prevent this issue in the future I am making up test tiles of all my underglazes so that I can see what the true colors are before applying them to my pieces. I discussed this with my teacher and can bring these with me to the beginning of the next class to be fired but until then am blind as to what colors I actually have in front of me. Once I have the underglaze issue under control I plan to move into using colored glazes as well as slip trailing and now know that before I do any work to make up test tiles to see what happens to the colors in the kiln.

I have bought a bunch of books on pottery to hopefully help fill in the blanks but most do not cover using underglazes all that much. I am not interested in wheel techniques at this point, wanting to focus on hand built forms. I ordered Erin Furimsky's DVD (love her work!) since she does a lot of decoration to her pieces at leather hard and that is what I want to do as well. I also subscribed to Pottery Making Illustrated this morning as well. Other than lots of practice and experimentation is there anything else I can do to get what I see in my head out onto my pieces?

Thank you once again for your input.

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

#6 3dogsathome

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Posted 17 March 2013 - 12:32 PM

I have been doing some reading and it seems like applying clear glaze over underglaze when it is applied to bisque ware can be tricky. I didn't think to ask my teacher how to do this since I planned to apply all my underglazes before firing to bisque but well the best laid plans and all that.... So I have a piece that did not come out of the kiln after bisque firing quite as I had hoped so I have applied some additional underglazes hoping to "rescue" the piece. The problem I now have is how to apply the glaze without smearing these newly applied underglazes. The next session of classe does not start up again for a month and I'd rather not wait that long to ask what I am sure to those of you with more experience is a simple question. To get the BEST results do I pour, sponge, brush or dip the piece? It is a large platter so dipping might be hard but I could do it I guess in a plastic tub if I had to just not sure if I could reuse the extra glaze after doing something like that or not.

As you can tell I REALLY need help and really really appreciate your time for doing so.

Terry


Hi Terry,

No problem with bisque firing the piece again....I do a lot of underglaze work covered with a clear glaze. Although you can certainly apply the underglaze directly on the greenware, I often find that bisque firing the piece first makes it easier to work on, depending on what form it is. Anyway, a second (or even more) bisque firing will not cause any problems and will prevent any smearing or bleeding when you apply the glaze. I prefer to dip my pieces into the clear glaze, and if the platter is too large to fit into the bucket, pour the glaze into a container large enough to handle it. Most of us keep some large containers or basins in our studio just for that purpose.

Good luck!

Barb

#7 Pompots

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Posted 17 March 2013 - 11:08 PM

It seems to me like it is a big deal of applying the clear glaze over the unfired underglaze, I have been doing that for a long time with lots of
success. Using a soft brush the undreglaze is not going anywhere. Please give it a try, im sure after you do it and get a grip of it, you will love
it.
Best
Pompeyo
PS. Attached is a picture of some napking rings i made with underglazes and clear glaze over bisque.

Attached Files

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#8 minspargal

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Posted 18 March 2013 - 09:16 AM

I like to put the under glazes on greenware and then fire. I work with red clay so after the bisque, i wet the piece and i can see if i need a another coat of underglaze before i sponge on the clear glaze.I like solid blocks of color no white or red clay showing through. I only sponge on the first coat to set the underglazes, after that i can brush on the next two coats. And yes test tiles are a good idea.

#9 Idaho Potter

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Posted 18 March 2013 - 06:27 PM

After reading all the above, the question that comes to mind is how important is this piece that needs a second application of underglaze? If it something that you could live with IF the underglaze smeared, then, go for it. On the other hand, if it is one-half of a matching pair, you'd be assured of a good finish if you bisqued it again.

I have used both approaches, and sometimes I'm lucky, sometimes not so much. I apply three coats of underglaze to greenware, bisque and then clear glaze. If interrupted while applying underglaze, sometimes I have to reapply after the bisque firing. I usually run the pot through the next bisque so I know the underglaze won't shift or bleed or smear. With careful application of the glaze you may succeed, but because I like really clear edge definition I've learned to do the second bisque.

#10 neilestrick

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Posted 19 March 2013 - 08:06 AM

We always apply underglaze and the clear glaze to bisque, without firing on the underglaze first. No problems.
Neil Estrick
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#11 perkolator

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Posted 19 March 2013 - 02:44 PM

many commercial UGs work on top of glaze just fine. try it and see how it works for you.

#12 Pugaboo

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Posted 20 March 2013 - 08:28 AM

I wanted to show you what it is I'll be coating with clear glaze. It's a large tray, the second item I have ever made, that when it came out of the kiln the Pug in the center was actually chocolate brown, not pale brown. I also added more colors to the field behind the pug blending them in more and also doing a light pouncing of white over to hopefully keep them a touch paler since they were kind of neon bright coming out of the kiln. To adjust the color for the Pug I used Amaco Sun Tan LUG whereas originally I used light brown. I have no idea what any of these colors are going to come out of the kiln looking like. The Amaco clear zinc free glaze arrived yesterday so now I just need to decide if I am going to dip, sponge, or brush it on the tray. I don't own my own kiln yet so attempting to apply the glaze without a second bisque firing is probably my best option. I wanted to thank everyone for their suggestions I really appreciate your input.


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




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