[Isculpt]

I use copper carbonate mixed in water to create nearly black "rusty" deposits in the crevices of my work. I apply it liberally to bisqueware and then sponge off the highlights within 5 minutes, then fire it to 06-04. Unfortunately it is somewhat inconsistent, resulting in the black effect being still evident in areas that have been scrubbed clean, while other work has too little of the residue in the crevices, or the residue is a light grey. I've never tried copper oxide. Is it used in the same way for the same purpose? Can anyone suggest why I'm getting such inconsistent results? And is there any advantage to mixing other additions into the copper carbonate-water mix?

And while we're on the subject, what does a girl have to do to get a deep brown residue from a similar style application of red iron oxide? Am I just not heating it high enough? At 04 it yields a soft medium light brownish pink.

Thanks, Jayne

[lcar]

if you haven't already, try Barnard Clay. It's my favorite for highlighting texture. I prefer using it on bisque. Paint it into cracks and wipe it off the smooth areas with a sponge. very dark brown to black. Looks great under translucent glaze. It has a high iron content and cheaper than the oxides.

Leanna

[Marcia Selsor]

For the technique you are using, try Val Cushing's underglaze wash recipe: 1/3 Frit 3110, 1/3 EP Kaolin and 1/3 stain. I think it would clean up better that a raw metal oxide especially something as volatile as copper carbonate. The Mason Black stain 6600 in the base should give you what you are looking for.
I also like Bernard slip and have used it in the above base for low temp soda firings at 01.

Marcia

[Kohaku]

Marcia Selsor, on 05 November 2012 - 04:52 AM, said:

For the technique you are using, try Val Cushing's underglaze wash recipe: 1/3 Frit 3110, 1/3 EP Kaolin and 1/3 stain. I think it would clean up better that a raw metal oxide especially something as volatile as copper carbonate. The Mason Black stain 6600 in the base should give you what you are looking for.

Also a lot cheaper and less toxic than copper carb!

[Isculpt]

I really hate to show my inexperience and ignorance of all things pertaining to glazing, but I'd like to follow your suggestions if you could provide just a bit more help. There is a local ceramics supply store where I assume that I can get the materials you mentioned, but they're a bit slim on information. Can you tell me what quantities should I ask for when I go there to purchase the items you mentioned? FYI, I have a small sculpture studio with low output.

In what way is copper carbonate "volatile"? I know that it is dangerous to breathe and that care should be taken to avoid skin contact. If I choose to replace the copper carbonate, what can I do with the two pounds of copper carbonate that I have? Maybe sprinkle it into a sawdust firing for color?

thanks, Jayne

Marcia Selsor, on 05 November 2012 - 07:52 AM, said:

For the technique you are using, try Val Cushing's underglaze wash recipe: 1/3 Frit 3110, 1/3 EP Kaolin and 1/3 stain. I think it would clean up better that a raw metal oxide especially something as volatile as copper carbonate. The Mason Black stain 6600 in the base should give you what you are looking for.
I also like Bernard slip and have used it in the above base for low temp soda firings at 01.

Marcia

[Isculpt]

Leanna, about this Barnard clay -- is it a readily available slip? Do I dilute it or ??? It sounds like a great substitute. thanks, Jayne

lcar, on 05 November 2012 - 02:36 AM, said:

if you haven't already, try Barnard Clay. It's my favorite for highlighting texture. I prefer using it on bisque. Paint it into cracks and wipe it off the smooth areas with a sponge. very dark brown to black. Looks great under translucent glaze. It has a high iron content and cheaper than the oxides.

Leanna

[perkolator]

Barnard Clay/substitute is a clay high in iron content and will come in dry form. It's fairly cheap since it's clay, so I'd get like 5# to play around with. Simply combine with water to make your wash. I suggest wearing gloves, the stuff stains like crazy.

As for the copper - it's not going to go bad on you, so just keep it; you'll always find a use for it at some point. as for toxicity, it's not really that toxic - but in the way you're using it it can cause contact dermatitis if you don't wear gloves and practice safe handling, like pretty much any of your glaze materials. in the kiln it's fairly volatile and the fumes you definitely don't want to breathe in just like all the other stuff that volatilize as you fire. Copper can be bad when you don't have a proper glaze to keep it from leaching into food on functional wares. Copper isn't really "expensive" nor is it cheap, but in the way you're using it it'd probably be more economical to use another material until you know specifically when you need copper vs another material for this type of application. Check out Digitalfire for info on Copper.

As for copper carb (CuCO3) vs copper oxide (CuO) -- the difference is chemical in terms of the oxygen/carbon molecules. So for pretty much any glaze colorant, the oxide form will be more potent than the carbonate form because, weight for weight, you get more of the metal/colorant in the oxide form since it doesn't have an extra couple molecules attached, taking up space. Once they go through chemistry change in the kiln, they become equal with one another. Hope this helps.

You mention wanting dark browns like you get with iron - why not use an iron wash/underglaze?

[Isculpt]

perkolator, on 06 November 2012 - 01:27 PM, said:

Barnard Clay/substitute is a clay high in iron content and will come in dry form. It's fairly cheap since it's clay, so I'd get like 5# to play around with. Simply combine with water to make your wash. I suggest wearing gloves, the stuff stains like crazy.

As for the copper - it's not going to go bad on you, so just keep it; you'll always find a use for it at some point. as for toxicity, it's not really that toxic - but in the way you're using it it can cause contact dermatitis if you don't wear gloves and practice safe handling, like pretty much any of your glaze materials. in the kiln it's fairly volatile and the fumes you definitely don't want to breathe in just like all the other stuff that volatilize as you fire. Copper can be bad when you don't have a proper glaze to keep it from leaching into food on functional wares. Copper isn't really "expensive" nor is it cheap, but in the way you're using it it'd probably be more economical to use another material until you know specifically when you need copper vs another material for this type of application. Check out Digitalfire for info on Copper.

As for copper carb (CuCO3) vs copper oxide (CuO) -- the difference is chemical in terms of the oxygen/carbon molecules. So for pretty much any glaze colorant, the oxide form will be more potent than the carbonate form because, weight for weight, you get more of the metal/colorant in the oxide form since it doesn't have an extra couple molecules attached, taking up space. Once they go through chemistry change in the kiln, they become equal with one another. Hope this helps.

You mention wanting dark browns like you get with iron - why not use an iron wash/underglaze?

Thanks for all the helpful information. I've tried using a brown or black underglaze, but I don't get that mineral look -- the slightly grainy, rusty, metal-shiny (if you can't come up with one word to describe it, try three!!) look of copper carbonate. When you say "iron wash", what are you referring to?
Jayne

[Marcia Selsor]

Isculpt, on 05 November 2012 - 07:42 PM, said:

I really hate to show my inexperience and ignorance of all things pertaining to glazing, but I'd like to follow your suggestions if you could provide just a bit more help. There is a local ceramics supply store where I assume that I can get the materials you mentioned, but they're a bit slim on information. Can you tell me what quantities should I ask for when I go there to purchase the items you mentioned? FYI, I have a small sculpture studio with low output.

In what way is copper carbonate "volatile"? I know that it is dangerous to breathe and that care should be taken to avoid skin contact. If I choose to replace the copper carbonate, what can I do with the two pounds of copper carbonate that I have? Maybe sprinkle it into a sawdust firing for color?

thanks, Jayne

Marcia Selsor, on 05 November 2012 - 07:52 AM, said:

For the technique you are using, try Val Cushing's underglaze wash recipe: 1/3 Frit 3110, 1/3 EP Kaolin and 1/3 stain. I think it would clean up better that a raw metal oxide especially something as volatile as copper carbonate. The Mason Black stain 6600 in the base should give you what you are looking for.
I also like Bernard slip and have used it in the above base for low temp soda firings at 01.

Marcia

Volitale ....Copper jumps and flashes when fired..inside the kiln. It is somewhat unstable, can tinge nearby pots with color.
Marcia

[tpots]

lcar, on 05 November 2012 - 02:36 AM, said:

if you haven't already, try Barnard Clay. It's my favorite for highlighting texture. I prefer using it on bisque. Paint it into cracks and wipe it off the smooth areas with a sponge. very dark brown to black. Looks great under translucent glaze. It has a high iron content and cheaper than the oxides.

Leanna

Hi,

How are you using the Barnard Clay - water down and apply as slip? Will it fire to cone 6 - 7?

This is a very economical way to bring out highlights with out all the chemicals.

Thanks,

[Marcia Selsor]

Leanna does high temperature wood firing among other things. I think she will chime in here soon.
I have used bernard slip as a stain in the underglaze recipe I mentioned earlier 1/3 frit 3110. 1/3 epk and 1/3 stain. I used it in low temmperature soda firings. It came out a golden buttery yellow.

Marcia