Refining Mesh of Materials

[CPottery]

Hi,

I'm trying to get the elusive oxidation copper red with localized reduction glaze to work. Everywhere I look it suggests 600 mesh silicon carbide is necessary to get the localized reduction.

The silicon carbide I have is 400 mesh. How can I increase the mesh of my silicon carbide?

[neilestrick]

I think it would be very difficult to mill down silicon carbide, since it's so hard and abrasive. Typically you would use a ball mill to reduce the particle size of glaze materials, but the SC will just wear down the balls. Just buy finer mesh SC and save the 400 for grinding lid seatings. You can get the fine stuff from lapidary supply shops online. You may actually need even finer than 600, so I'd get some 800 and 1000, too, as long as you're ordering.

[CPottery]

57 minutes ago, neilestrick said:

I think it would be very difficult to mill down silicon carbide, since it's so hard and abrasive. Typically you would use a ball mill to reduce the particle size of glaze materials, but the SC will just wear down the balls. Just buy finer mesh SC and save the 400 for grinding lid seatings. You can get the fine stuff from lapidary supply shops online. You may actually need even finer than 600, so I'd get some 800 and 1000, too, as long as you're ordering.

Thank you. Do you have any experience with the locally reduced glazes? I'm having a hard time finding any thorough details on them like firing schedules, glaze makeup, variations, etc...

[CPottery]

I'm looking at lapidary supply shops now. They seem to categorize the silicon carbide by "Grit" is this different than "Mesh"?

1 hour ago, neilestrick said:

I think it would be very difficult to mill down silicon carbide, since it's so hard and abrasive. Typically you would use a ball mill to reduce the particle size of glaze materials, but the SC will just wear down the balls. Just buy finer mesh SC and save the 400 for grinding lid seatings. You can get the fine stuff from lapidary supply shops online. You may actually need even finer than 600, so I'd get some 800 and 1000, too, as long as you're ordering.

 

[neilestrick]

Just now, CPottery said:

Thank you. Do you have any experience with the locally reduced glazes? I'm having a hard time finding any thorough details on them like firing schedules, glaze makeup, variations, etc...

I've done a few tests, but haven't pursued it fully to get it to work properly. The thing I do know is that it's really easy to get too much SC in the glaze. You only need a tiny amount, like 1/4 of 1% if I remember correctly. One theory I've wanted to test is holding temp at bisque temps, as that is what I would do when firing a gas kiln. Hold at cone 012-06 for 45 minutes to give the reduction a chance to do its thing before continuing up with the firing.

Grit and mesh are basically the same.

[CPottery]

2 minutes ago, neilestrick said:

I've done a few tests, but haven't pursued it fully to get it to work properly. The thing I do know is that it's really easy to get too much SC in the glaze. You only need a tiny amount, like 1/4 of 1% if I remember correctly. One theory I've wanted to test is holding temp at bisque temps, as that is what I would do when firing a gas kiln. Hold at cone 012-06 for 45 minutes to give the reduction a chance to do its thing before continuing up with the firing.

Grit and mesh are basically the same.

Thank you again! That's such an interesting thought! I know exactly what you mean, if firing with a gas kiln I would do the same, hold around bisque temp. However, I thought that was for body reduction? Pulling the iron out to the surface of the clay not the glaze. I can see how that would still effect the glaze though.

[neilestrick]

4 hours ago, CPottery said:

Thank you again! That's such an interesting thought! I know exactly what you mean, if firing with a gas kiln I would do the same, hold around bisque temp. However, I thought that was for body reduction? Pulling the iron out to the surface of the clay not the glaze. I can see how that would still effect the glaze though.

It is for body reduction, but you're also reducing the glaze, which is why you can do the rest of the firing in a neutral atmosphere and still have a reduced glaze. Glazes don't reduce well once they've melted. For instance, some shino glazes need to be reduced early like cone 012, because the soda ash in them melts very early.

[CPottery]

On 7/17/2020 at 5:15 PM, neilestrick said:

It is for body reduction, but you're also reducing the glaze, which is why you can do the rest of the firing in a neutral atmosphere and still have a reduced glaze. Glazes don't reduce well once they've melted. For instance, some shino glazes need to be reduced early like cone 012, because the soda ash in them melts very early.

Right! Hmm, very interesting. Thanks for the information and advice!

[Min]

Tom Turner has a very good article on silicon carbide oxidation red glazes. http://www.tomturnerporcelain.com/_files/CopperRed_35DE.pdf

 

[PeterH]

You may be interested in an earlier thread on this topic, and my summary of an old paper on the topic.

PS Ian Currie's book is now at https://s3-us-west-2.amazonaws.com/wiki-glazy-org/documents/IanCurrieStonewareGlazes.pdf

Reduced copper glazes are discussed on page numbers 189-193 (but local reduction is only mentioned in passing)

[docweathers]

Thanks