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riverheights

Cone 5 Speckled Glaze

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Hello,

I'm a studio tech and am looking for a speckled white glaze with melty brown speckles like in this image for our students. The colour is a bit off in the image - the speckles are a brown, rust colour.

I know that the clay is likely speckled buff, but we are locked to B-Mix as a clay body so we would need a glaze. 

I tried adding both granular ilmenite and granular rutile to our white glaze. The ilmenite didn't melt at all, unsurprising. I was hoping the rutile would melt similar to the glaze in the image - but it didn't seem to melt at all.

Is this kind of glaze only obtainable by using a white glaze over a speckled clay body, or am I doing something wrong with the rutile? 

Thank you! 

IMG_2836.jpg

Edited by riverheights

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You could also try iron spangles. There is an interesting article on making your own speckles to add to glaze here, about half way down the page. (spoiler alert, it looks like a heck of a lot of work)

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We fire to cone 5. We were thinking of trying a cone 6 but Bmix is a cone 5. Also wondering if we add a longer hold, maybe that would help. I thought there would be some melt with the rutile. 

I worry about manganese because it’s so hazardous  

See attached for my samples. No melt at all!

24233393-1C64-43E3-9BC7-E9B0359CE8CA.jpeg

FB3A740C-731A-4C45-9B81-BDBFB8807AE0.jpeg

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Your picture definitely looks like a 'plain' white glaze over speckled clay...  

This may be too speckled for you, but Coyote's "Oatmeal" is a commercially available glaze that fits the description of white with brown speckles.   The pic is a set of cat food/water bowls made with Standard's 112 (speckled brown) clay, so some of the larger spec's are from the clay, but it should give you a good idea of what it looks like at ^5.  (Unfortunately, since it's a commercial glaze, I have no idea what they put in it to create the specks.)

20170218_214632a.jpg.ac98b58412a15100f570757ca0f42dd1.jpg

 

this mug is same glaze on a white stoneware - also at ^5

20170218_215414.jpg.6acd8527e34a13d64ab6241e77fc8116.jpg

Edited by Rockhopper

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You might try mixing a B-mix slip that has 'black spots' in the slip.  Apply the slip as last step before bisquing the ware that will have the white glaze applied.  
This technique, adding 'stuff' to a thick slip of the same clay body that is used for throwing (or hand building) the item, has worked well for me for several years.  

This route does require that students must think about the glaze to be used at the time they make the item - but thinking is a major part of successful studio work. 

LT
 

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It's difficult to get speckles in the glaze that will look like speckles in the clay. There's something about the specks coming through from the clay that look and behave differently than when they're suspended in the glaze.

The size of the granular material will have a large effect on your success, so compare the mesh sizes that you can get from different suppliers.

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On 3/5/2019 at 2:09 PM, liambesaw said:

Manganese toxic as a vapour, if you fire in a school during class time that's probably a no-go, but after the firing is not as hazardous

We fire in a community centre, and our kilns vent outside. Do you think that would be a problem? 

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On 3/5/2019 at 3:55 PM, Rockhopper said:

Your picture definitely looks like a 'plain' white glaze over speckled clay...  

This may be too speckled for you, but Coyote's "Oatmeal" is a commercially available glaze that fits the description of white with brown speckles.   The pic is a set of cat food/water bowls made with Standard's 112 (speckled brown) clay, so some of the larger spec's are from the clay, but it should give you a good idea of what it looks like at ^5.  (Unfortunately, since it's a commercial glaze, I have no idea what they put in it to create the specks.)

20170218_214632a.jpg.ac98b58412a15100f570757ca0f42dd1.jpg

 

this mug is same glaze on a white stoneware - also at ^5

20170218_215414.jpg.6acd8527e34a13d64ab6241e77fc8116.jpg


This is lovely! 

 

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3 minutes ago, riverheights said:

We fire in a community centre, and our kilns vent outside. Do you think that would be a problem? 

No, I don't think it would be a problem if the kilns are vented to the outside.

Did you try granular magnetite yet? 

 

Edited by liambesaw

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