Uneducated but enthusiastic ceramicist looking for advice about stoneware glazes

[Bauhaus]

Hi there, I’m a fine artist who has recently got into ceramics, stoneware to be specific. Unfortunately I’m not tutored in it to any technical level and I’m having to pick up information as I go. Where I live it’s very expensive to buy that kind of education, so I’m trying my best to wing it. 

I’m confused about glazes. I’m firing to cone 6, 1100 bisc, then 1230 for glazing. I’ve not started glazing but I’ve bought some glazes from the local shop. I’ve been trying to get advice from them but I think they don’t know a lot about ceramic production and are more specialists in kiln technology. They accidentally sold me some cone 4 glazes which they’ve agreed to exchange. They also sold me some cone 6 glazes made by various different manufacturing companies. I’ve now realised perhaps I should be using glazes just by one manufacturer? Will it be a problem to paint different glazes side by side in an image? Say, a flower with pink petals made by one company and the pollen centre of the flower by another? 

Then there is the question of the transparent over glaze. Do I need to use the same company manufacturer for that?  Is there one which works well covering a range of different colour glazes from different companies?  Is it suitable for functional ware?

 I’m thinking I may have to just return all the glazes I bought and buy some online, or if they only allow me to exchange, buy something I know I can get the rest of the range from online. They’re limited in stock in this shop, hence the picking different things from different companies.

 I’m also thinking what if I just paint a load of things and I get a really great effect which is a result of the mixture?

This is my first post here, but I’ve been reading for a while. Thanks.

 

[Hulk]

Hi Bauhaus,

Whether store bought or mixed in your studio, you'll likely want glazes that a) fit your clay and b) behave well, per your processes.

Glazes from the same or different sources may, or may not, play well together in general, let alone how you wish.
Some glazes stay put well; others move. Some glazes react well with each other, some do not...

Transparent is typically used over underglazes but may not stay "over" another glaze.

For your clay (clays may be more challenging...), a clear glaze that fits well (no crazing or shivering), goes on well, fires well, and is durable and looks good - all important for functional ware. I developed a liner glaze over the course of several years...

There are many sources of info on glazes; this forum, and Tony Hansen's website are two.

Here, try some search strings to find archived threads that interest you, e.g. "crazing" and "glaze fit"

Tony Hansen's site, see the Articles sub menu, also the Troubles sub menu, Projects, Recipes, etc.
Where do I start in understanding glazes? (digitalfire.com)
 

[Babs]

Ok, Bisque cone 6. Way too high. Pots wont take the glaze, they will not be porous enough

Bisque Cone 06 to 04.

Some great books around, bibles.

Where are you firing your stuff. If testing, ie noting down what you put on what for future reference, make test tiles or put waster biscuits of clay under each pot , can be reused, in case glazes run off your pots.

Test tiles a must really.

 

[neilestrick]

If you want to paint images like flowers and whatnot, then you want to use underglazes, not glazes. Glazes will generally run/flow where they contact each other, and any imagery you paint on will bleed and move and blur. Glazes do not require a clear glaze over them, and the clear glaze will mix with the other glaze and change how it looks. Underglazes, however, will not bleed where they contact each other, are not fluid, and have the added benefit of being the same color before and after firing so they're easy to work with. Underglazes require a glaze over them in order to be durable and food safe.

[Bauhaus]

1 hour ago, Babs said:

Ok, Bisque cone 6. Way too high. Pots wont take the glaze, they will not be porous enough

Bisque Cone 06 to 04.

Some great books around, bibles.

Where are you firing your stuff. If testing, ie noting down what you put on what for future reference, make test tiles or put waster biscuits of clay under each pot , can be reused, in case glazes run off your pots.

Test tiles a must really.

 

I think the bisque firing is not cone 6. 1100 Celsius, is that cone 4? The shop has kiln rental and an engineer who works there. I was asking him for advice on how to fire in the process I wanted: bisque then decorate/glaze. He seemed to think this would work, then a higher temperature for glazing. He told me to leave 3mm of space in case the glaze runs.  

I’m wondering if I can use a paint on underglaze like this https://www.potclays.co.uk/ready-mixed-glazes-colours-pencils-crayons-mayco-underglazes if it’s bisque fired to 1100 Celsius. It says to apply to cone 4 bisque, I’m guessing because of optimum porosity.

[Bauhaus]

6 hours ago, Hulk said:

Hi Bauhaus,

Whether store bought or mixed in your studio, you'll likely want glazes that a) fit your clay and b) behave well, per your processes.

Glazes from the same or different sources may, or may not, play well together in general, let alone how you wish.
Some glazes stay put well; others move. Some glazes react well with each other, some do not...

Transparent is typically used over underglazes but may not stay "over" another glaze.

For your clay (clays may be more challenging...), a clear glaze that fits well (no crazing or shivering), goes on well, fires well, and is durable and looks good - all important for functional ware. I developed a liner glaze over the course of several years...

There are many sources of info on glazes; this forum, and Tony Hansen's website are two.

Here, try some search strings to find archived threads that interest you, e.g. "crazing" and "glaze fit"

Tony Hansen's site, see the Articles sub menu, also the Troubles sub menu, Projects, Recipes, etc.
Where do I start in understanding glazes? (digitalfire.com)
 

Thanks for this glaze link, I am beginning to understand that what I learned from a course at a community college is so basic it’s almost criminal the way we’ve been dumbed down about this stuff. I was taught ceramics to pre-degree level, and did an adult education course. I’m guessing degree level ceramics is where you learn the technical side, or at least I hope they do. If they don’t teach it there and everyone is relying on commercial supplied brush on glazes then that’s a significant gap in knowledge in the community. 

[Bauhaus]

1 hour ago, neilestrick said:

If you want to paint images like flowers and whatnot, then you want to use underglazes, not glazes. Glazes will generally run/flow where they contact each other, and any imagery you paint on will bleed and move and blur. Glazes do not require a clear glaze over them, and the clear glaze will mix with the other glaze and change how it looks. Underglazes, however, will not bleed where they contact each other, are not fluid, and have the added benefit of being the same color before and after firing so they're easy to work with. Underglazes require a glaze over them in order to be durable and food safe.

Do you have any recommendations for underglaze and clear glaze? Due to lack of a dedicated studio and space I’m sticking to brush on readymade stuff. When I get a studio (when I start selling) I’ll probably get more experimental with powders and so on.

[Chilly]

Hi @Bauhauswelcome to the forum.

Where in England are you, I might be able to point you to more help?

Cones and temperature can only be compared if you know which style of cone, and which firing rate is used.

http://c0dc6bc9-fdd4-4b7b-883d-06ca9f81bb37.usrfiles.com/ugd/0c3047_558b1411295f4e049829c9233fe27f91.pdf

You will see that 1100c appears in several columns.

Usual practice is to bisque at cone 06-04 and then glaze fire at anything from the same for earthenware, to cone 6 for high(UK)/mid(US) to Cone 8 or higher.  Stating temperature tends to confuse the issue.

[Bauhaus]

1 hour ago, Chilly said:

Hi @Bauhauswelcome to the forum.

Where in England are you, I might be able to point you to more help?

Cones and temperature can only be compared if you know which style of cone, and which firing rate is used.

http://c0dc6bc9-fdd4-4b7b-883d-06ca9f81bb37.usrfiles.com/ugd/0c3047_558b1411295f4e049829c9233fe27f91.pdf

You will see that 1100c appears in several columns.

Usual practice is to bisque at cone 06-04 and then glaze fire at anything from the same for earthenware, to cone 6 for high(UK)/mid(US) to Cone 8 or higher.  Stating temperature tends to confuse the issue.

Hi @Chilly I’m in Bournemouth, Dorset.

Thank you for the link, I don’t understand it at all. I’ve contacted the clay manufacturer and asked them for firing information. I think I need to get exact instructions like that in future because that seems to be the safest way to work things out. I’ve also asked what glazes are suitable because they sell those too. 

[Babs]

1100C is about cone 03. Too high for bisque imo

Cones are numbered with a 0 in front of numeral  which diminishes (as a neg maths does ),as the temp rises until  01 then cone 1, 2 as temp rises. Most folk bisque to 04 these days but depending on clay body, 40 plus years ago folk bisqued to cone 08.

Be clear of this when ordering stuff and bisquing glazing.

Good practice to place banks of cones on shelves to find out what is happening in your kiln.

Keep log book of your firing and results.

[Babs]

Nowhere do you state the clay you are using. On the box , bag it will give a firing range.

This will determine what cone you fire to.

Cone determines heatwork done, thus the cones placed on each shelf to indicate what happened on each shelf. So a fast firing may reach temerature but not had sufficient heatwork done to mature the glazes.   

You will have many aaaah moments.

Enjoy!

If making functional pots, the clay needs to reach the upper level of its firing range to be vitrified sufficiently to retain any liquid placed in it.

Do take lots of notes and ask many questions.

So much to learn in this field.

[Bauhaus]

1 hour ago, Babs said:

Nowhere do you state the clay you are using. On the box , bag it will give a firing range.

This will determine what cone you fire to.

Cone determines heatwork done, thus the cones placed on each shelf to indicate what happened on each shelf. So a fast firing may reach temerature but not had sufficient heatwork done to mature the glazes.   

You will have many aaaah moments.

Enjoy!

If making functional pots, the clay needs to reach the upper level of its firing range to be vitrified sufficiently to retain any liquid placed in it.

Do take lots of notes and ask many questions.

So much to learn in this field.

Hi @Babs it’s this https://www.scarva.com/Mobile/en/Scarva-Earthstone-ES40-Handbuilding-White-Clay/m-m-6.aspx

 

the shop I’m getting it from are doing the firing and gave me specific temperatures very confidently (1100 bisc, 2130 glaze) so if this is wrong I am wondering whether their kiln is particular in that it somehow works in their kiln (maybe doesn’t get up to temperature?) or they know from others that these are the temperatures? After speaking to a friend who thinks there are all sorts of variables for why they did this.

difficulties like this are learning experiences for me, for sure. I note everything down, I walk around with a note book and quote people as they talk so I can be sure they definitely say exact things, and I double check with people that they said what I noted down. 

[Roberta12]

@Babs is correct, she is pointing you in the right direction.  It does seem that you are firing at too high of a temp for bisque.  Your clay is rated for much higher firing temps than the Cone 4 glaze you have.   You will have to have glazes and clay that match firing temps.  It takes a lot of research to understand this field.  

 I had to get most of my information from books from the library, books that I purchased, books that I borrowed, and then when more information became prevalent on the internet,  that became a source.   I am still always in search of more information. This is the beginning of a long and interesting journey for you.   Keep asking questions and this will begin to make sense. 

Roberta

[neilestrick]

10 hours ago, Bauhaus said:

Do you have any recommendations for underglaze and clear glaze? Due to lack of a dedicated studio and space I’m sticking to brush on readymade stuff. When I get a studio (when I start selling) I’ll probably get more experimental with powders and so on.

I don't know what you have available, but I like Speedball underglazes, and they have a nice clear glaze, too. Amaco makes nice underglazes, too, but I see more color shifting in those when fired to cone 6. Get some small jars of whatever you have available and do some testing.

[Bauhaus]

30 minutes ago, neilestrick said:

I don't know what you have available, but I like Speedball underglazes, and they have a nice clear glaze, too. Amaco makes nice underglazes, too, but I see more color shifting in those when fired to cone 6. Get some small jars of whatever you have available and do some testing.

I was considering getting what Scarva recommend as what would be compatible with their clay. That sort of small jar stuff is definitely the kind of thing I am comfortable working with for now. I’m a painter, first. Ceramics is like my new canvas!

[Bill Kielb]

14 minutes ago, Bauhaus said:

am comfortable working with for now. I’m a painter, first

Underglazes should allow you to practice your brush art. Generally  It does take some getting used to and lots of testing to get everything just so.

lots of possibilities though. A couple samples below.

 

Edited June 12, 2022 by Bill Kielb

[Min]

@Bill Kielb, lovely pots and brushwork! Is that some of your work?

[oldlady]

bauhaus,  what color is your clay?   if it is white, why not try a slip made from your clay body and a colorant?  some are oxides or carbonates.  there are other blended colorants available.   i think in the uk they might be called pigments, in US they are called stains.  the reason i suggest silp instead of underglaze is the very high cost of underglazes at both potclays and scarva.   i am math illiterate but if your supplier sells you a tiny amount of colored underglaze for almost twenty pounds, you might ask about buying colorants separately.   that way, you can color slips, glazes and washes without having to buy a container of each product.   

there are excellent books available with plenty of photos and recipes for you to try.  it has been several years but i remember the book with Bible in it's title has an error in it with a reversal of the titles for cone numbers.   a major error in my estimation.

you will have to be the teacher in learning how to design, fire and glaze your work..   you might look for what we call a Paint Your Own Pottery shop where for a small investment in a white earthenware  figurine, (pick something you can put lots of different colors on)  and try out the store's supply of underglazes.   they will fire it for you and glaze it with a clear glaze to show the colors which will then be glossy and not flat as you have painted them.

this experience will show you a lot about using colors even if it is only earthenware that is fired much cooler than your stoneware.   ask questions while you work and the first of these will be "are you the person in charge of the kilns?"   if yes, ask if it would be convenient to discuss firing right now or maybe make an appointment for a time to do so.   start a notebook right there.

Edited June 12, 2022 by oldlady

[Bauhaus]

17 minutes ago, oldlady said:

bauhaus,  what color is your clay?   if it is white, why not try a slip made from your clay body and a colorant?  some are oxides or carbonates.  there are other blended colorants available.   i think in the uk they might be called pigments, in US they are called stains.  the reason i suggest silp instead of underglaze is the very high cost of underglazes at both potclays and scarva.   i am math illiterate but if your supplier sells you a tiny amount of colored underglaze for almost twenty pounds, you might ask about buying colorants separately.   that way, you can color slips, glazes and washes without having to buy a container of each product.   

there are excellent books available with plenty of photos and recipes for you to try.  it has been several years but i remember the book with Bible in it's title has an error in it with a reversal of the titles for cone numbers.   a major error in my estimation.

you will have to be the teacher in learning how to design, fire and glaze your work..   you might look for what we call a Paint Your Own Pottery shop where for a small investment in a white earthenware  figurine, (pick something you can put lots of different colors on)  and try out the store's supply of underglazes.   they will fire it for you and glaze it with a clear glaze to show the colors which will then be glossy and not flat as you have painted them.

this experience will show you a lot about using colors even if it is only earthenware that is fired much cooler than your stoneware.   ask questions while you work and the first of these will be "are you the person in charge of the kilns?"   if yes, ask if it would be convenient to discuss firing right now or maybe make an appointment for a time to do so.   start a notebook right there.

My clay is white. I have had stains suggested to me by the shop, but they were in powder form and I’m doing this in a multi purpose desk in the corner of my dining room, so I prefer the simplicity and ease of a brush on glaze from a jar. It’s the cleanest, least risky way for me to do things right now without a proper dedicated space for ceramic work. I don’t mind the cost of the brush on underglazes. I have a certain amount of money I’m happy to spend on materials, and I think I can make it back with sales eventually.  I do appreciate all of the suggestions though! They will be helpful for the future when I get more space.

[Magnolia Mud Research]

4 hours ago, Bauhaus said:

I’m a painter, first. Ceramics is like my new canvas!

early on I was is both a painting class and a ceramic class in the same semesters at school;  I created a research project to see how many of my painting materials would survive firing on clay; so I made some bisqued objects and did some painting on them, and sent them to the gas kiln.  
all of the paints that contained metal elements left a visual mark, not necessarily the color as they would have been on canvas, the non-metal paints simply burned off clean  (take pictures before sending items to the kiln to keep up with where colors are especially for the marks that disappear).

I began to use the paints that did survive the kiln firing as part of my glazing technique.  Cobalt blue paint over or under clear glaze fired to a beautiful blue;  paints with iron left strong marks; and others. 

Try it, you will learn what happens.  once I found what did what, I also got watercolor and crayons to make marks.  yes, this is an approach not listed in the ceramic or painting textbooks.  

LT

[neilestrick]

4 hours ago, Bauhaus said:

I’m a painter, first. Ceramics is like my new canvas

You'll like underglazes then. The color in the jar is the color they'll fire to. When you layer them you'll get some bleed-through of darker colors into lighter colors, but that can add a lot of depth to the surface. They don't mix like paints- yellow and blue will not make green- but you can tweak them pretty easily using colors that are next to each other on the color wheel- blue and green to make blue-green. You can also lighten and darken them with black, white, and gray. It requires testing, though, because the color you mix won't necessarily be the same after firing because some colorants are stronger than others. For instance, blue and black tend to overpower other colors, so what looks good as a 50/50 mix before firing might need a 90/10 mix.

This platter is done with Speedball underglazes, fired to cone 6 on porcelain. It looks like Scarva carries Speedball, and underglazes are compatible with most any clay body. The only thing to watch out for is if you're firing to cone 6, some colors may change. Speedball colors all hold very well, but the Royal Blue and Red tend to flux out at cone 6 and get rough. Their other blues and reds do fine. Carmine red is a nice color. Amaco Velevet underglazes are very nice, but more expensive.

[Bill Kielb]

8 hours ago, Min said:

lovely pots and brushwork! Is that some of your work?

Those are my pots but that is my Marcia’s brushwork. She is a portrait artist, my job is to throw the shape she devised for her decoration on command and I also need to make sure the glaze works regardless of how she decorates. Sort of like the OP …… just a different canvass for her. It’s why we spent a whole summer testing glazes with various thicknesses and layers of underglaze. My airbrush skills are ok though but Marcia paints daily. I have some skills but she is crazy good at painting.

[Bauhaus]

I just got back from picking up my “bisque fired” stoneware. Another person who worked there informed me their colleague had made a mistake and the kiln was set too high, however to save it they said I should paint 3 layers of underglaze with a hairdryer drying each layer, then paint transparent glaze over immediately. Apparently this will help the glaze to adhere. Next time, they said I should fire bisc stoneware to 1040 max. 

[Callie Beller Diesel]

Typically we see 1000 C as the usual bisque temperature from the UK and other places on the right side of the Atlantic. I could see using the 1040 temperature if you were working with a red clay, or a white earthenware that contains more than the usual amount of sulphur or other organics to burn off that might cause glaze flaws later. But that’s not probably going to be your first concern.

 In terms of painting pieces, it’s a really good idea for anyone who’s new to ceramics to make a few test pieces to see how their new chosen materials react together. Mixing brands of underglazes and glazes can be, and is done all the time. Unfortunately, the manufacturers don’t usually provide information on how their glazes mix with other brands, so you have to play around with it a bit yourself to get a feel for what will happen. 

Looking at the Scarva ES40 listing, I notice they recommend a top temperature of cone 9/1280 C, and suggest it for use as a tile/sculpture body. If you plan on making functional ware, that description would indicate to me that the finished ceramic at cone 9 might still be more porous than you’d want for food use items or vases that need to hold water. You would have to test the porosity of a fired piece to confirm, but that would be a project that you can put off for this first bag of clay. The reviews do say it’s quite nice for hand building, so for some first projects and to figure out how clay moves and behaves I’d use up what you have with maybe more decorative things/flower pots in mind.  You can check with Scarva for suggestions on a good clay for functional pots the next time you go shopping.

Especially when you’re first learning how to work with clay, there is a LOT of things that you’ll have to learn the feel for. The learning curve can be kind of steep and frustrating, but if you come at it with a sense of exploration, curiosity and play, it can be more rewarding. Try not to go into any of your first projects with your heart dead set on a specific outcome, but instead approach with a “I wonder what will happen if..” mindset.   

 

[Babs]

18 hours ago, Bauhaus said:

I just got back from picking up my “bisque fired” stoneware. Another person who worked there informed me their colleague had made a mistake and the kiln was set too high, however to save it they said I should paint 3 layers of underglaze with a hairdryer drying each layer, then paint transparent glaze over immediately. Apparently this will help the glaze to adhere. Next time, they said I should fire bisc stoneware to 1040 max. 

That is really disappointing.

Good luck with the glazing!!

I would do a test piece, may save you futile hours of underglaze and glazing not to mention the expense of the material.

Heating the pot prior to glazing may help but ......

Can't believe a professional establishment made this 101 firing mistake!

Did you have a full kilnful?