Tenacious Stain(s)?

[Ben xyz]

In trying to play up textures on some bisque ware, I am considering the use of what the studio I work out of calls stains (or washes, depending on how they're being used): Cobalt Carbonate, Red Iron Oxide, Rutile, Chrome Oxide, and Copper Carbonate.  Though will be doing tests, curious is anyone's found one or more of these more likely to burn through a glaze (applied on top at cone 6). Of course, it will depend on what glaze  goes over it, hence the tests. Curious about such experiences with any of them. Thanks.

[Callie Beller Diesel]

A few points in no particular order:

-Most of the ceramics community will call oxides mixed with water a wash. Calling it a stain can be confusing, because stain also refers to a man made ceramic pigment. There’s a few companies that make them, but Mason is the most prevalent one in North America. I’m not saying your studio is doing it wrong, I only mention that because we see a lot of posters from all over the world here, so it’s good to establish definitions to limit confusion.

-Whether or not a wash will show through a glaze depends very, very heavily on how it’s applied. How thickly the stain is applied, how thickly the glaze is applied, and how opaque the glaze is or isn’t will affect the end results. The base glaze’s chemistry and other colourants can also play a significant role. The maddening answer we have to give you is that because it’s very situation dependant, there’s going to be no getting around doing the testing. Our answers have to be a bit vague because there’s too many variables. That said, there’s some generalizations we can make, and there’s some interesting possibilities to watch for in your testing. 

-Cobalt is a very powerful colourant, and it’s easy to over apply it. Usually folks don’t use the carbonate as a wash, because it’s more difficult to tell how thick you’ve put it on due to it’s light lilac-ish shade. Cobalt oxide (which is black) is more visible, and can be painted like Sumi ink. It doesn’t tend to run or bleed, unless the base glaze is also pretty mobile. 

-RIO is one of the more common washes, and it highlights details nicely without being expensive. It’ll impart a rusty brown colour of some kind. If you apply it too thickly, it may cause any glaze applied over it to crawl. If you go too thin, some glazes will eat it. 

-Chrome can be pretty overwhelming as well. It mostly goes brown ish if uncovered, and if there’s tin in the glaze you cover it with, there’s a good possibility of pink flashing occuring. Pieces with chrome washes may affect pieces with tin glazes that are placed in the same kiln. 

-Copper goes a dull metallic colour if overapplied. If underapplied it will sort of vanish. It will be more black than green, unless covered with a glaze with sodium in it. Or if there’s a little sodium frit or feldspar mixed in with the wash.

-Rutile won’t look like much, until it does. It is most often beige by itself. It might  be beige with other things as well, but at cone six it *might* contribute to interesting crystallization/floating blue effects IF the covering glaze’s chemistry is right and IF the firing cycle allows it to happen. This one is a big “test it and see what happens” situation. 

[Ben xyz]

7 hours ago, Callie Beller Diesel said:

A few points in no particular order:

-Most of the ceramics community will call oxides mixed with water a wash. Calling it a stain can be confusing, because stain also refers to a man made ceramic pigment. There’s a few companies that make them, but Mason is the most prevalent one in North America. I’m not saying your studio is doing it wrong, I only mention that because we see a lot of posters from all over the world here, so it’s good to establish definitions to limit confusion.

-Whether or not a wash will show through a glaze depends very, very heavily on how it’s applied. How thickly the stain is applied, how thickly the glaze is applied, and how opaque the glaze is or isn’t will affect the end results. The base glaze’s chemistry and other colourants can also play a significant role. The maddening answer we have to give you is that because it’s very situation dependant, there’s going to be no getting around doing the testing. Our answers have to be a bit vague because there’s too many variables. That said, there’s some generalizations we can make, and there’s some interesting possibilities to watch for in your testing. 

-Cobalt is a very powerful colourant, and it’s easy to over apply it. Usually folks don’t use the carbonate as a wash, because it’s more difficult to tell how thick you’ve put it on due to it’s light lilac-ish shade. Cobalt oxide (which is black) is more visible, and can be painted like Sumi ink. It doesn’t tend to run or bleed, unless the base glaze is also pretty mobile. 

-RIO is one of the more common washes, and it highlights details nicely without being expensive. It’ll impart a rusty brown colour of some kind. If you apply it too thickly, it may cause any glaze applied over it to crawl. If you go too thin, some glazes will eat it. 

-Chrome can be pretty overwhelming as well. It mostly goes brown ish if uncovered, and if there’s tin in the glaze you cover it with, there’s a good possibility of pink flashing occuring. Pieces with chrome washes may affect pieces with tin glazes that are placed in the same kiln. 

-Copper goes a dull metallic colour if overapplied. If underapplied it will sort of vanish. It will be more black than green, unless covered with a glaze with sodium in it. Or if there’s a little sodium frit or feldspar mixed in with the wash.

-Rutile won’t look like much, until it does. It is most often beige by itself. It might  be beige with other things as well, but at cone six it *might* contribute to interesting crystallization/floating blue effects IF the covering glaze’s chemistry is right and IF the firing cycle allows it to happen. This one is a big “test it and see what happens” situation. 

Thanks for the clarification of terms, Callie. Helpful to know. After firing my 'wash' tests (and the glazes over them), I may also try using an underglaze on greenware first, bisque fire, then apply a regular opaque glaze on top; proceed to use a sponge or brush, sandpaper, steel wool, etc to reveal the underglaze coloring where needed in order to play up the textures (then fire at cone 5). Perhaps it will be easier to control the results this way.

Appreciate the descriptions of what colors may occur with the washes I'm initially testing. I was told by a ceramicist that this type of burn-through effect can happen more readily when firing at come10.

[Callie Beller Diesel]

On 12/7/2022 at 4:18 AM, Ben xyz said:

then apply a regular opaque glaze on top

Again, it super depends on what the glaze normally does, and what you mean by regular. I also don’t know that I agree with the person that says burn through happens more frequently at cone 10. An example would be a glaze that is pretty opaque like a floating blue (either cone 6 or 10) that breaks and pools over texture. Something like that might not need any removal techniques. You can get some really interesting variations by putting a single glaze over a white clay body with some kind of iron based  decoration, whether it’s a wash or a textured slip, or something else.

On the other side of the possibilities, an opaque glaze that has a lot of saturated colourants in it (like a tenmoku for example), might not allow for any bleed through because the glaze just overwhelms the wash. 

If you want to use the underglaze to highlight texture but in a different colour than the glaze, that also has lots of fun possibilities. 

If you get elaborate with your tests, make sure you take lots of notes. Document stuff as much as you can. 

[oldlady]

testing is very important so recording what you do is critical.  i had a friend who kept each glaze to one page of a 3 ring notebook.  she noted the base glaze by number on both the test and the page it was recorded on.   she wrote the recipe and if she tested various mason stains to get other colors, each color got it's own page.   i do something similar but often wish i had here more descriptive notes.  some of mine say,  never again!  but not why.  the reason for the never again is so if you find what looks like a nice color on someone else's clay, you will know it looks awful on yours because the recipe is right there to compare.