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What’s the best way to glaze texture?

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7DAAC361-8FE0-4E9F-8338-96677855F034.jpeg.1cdd72ba72cf48c62c9b58da7f44582a.jpegDear Potters,

I’ve recently delved into glaze making and had finally settled on a clear I really liked - Tony Hansen’s 20 x 5. However, I’ve noticed that for my more detailed/textured work that the glaze cracks after dipping just at the base of the textured surface. I have attached images. I’m wondering:

- Is the glaze applied too thick / not mixed with enough water?

- is there too much clay in the glaze (20 x 5 has 20% kaolin - I used Eckalite 2)

- or would it just be much better to brush on a clear glaze so I can somewhat control where the glaze goes?

i tried to scratch out the cracks and buff with a brush. The kiln is on and I’m hoping the glaze will be okay, but moving forward I would like the glaze to either dip or brush without these cracks.

Thank you in advance!

 

 

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First Hopefully they melt nicely and your simple fix at glaze time is enough.  Maybe spraying would be more successful or find a clear that allows this shape to be dipped more easily.  What is the mixed specific gravity of this glaze as shown if you know.

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Thank you for your help Callie and Bill. :) 

I just unpacked the firing, and thankfully the glaze was fairly forgiving. I do think spraying would be a superb option, but a spray booth isn't really within my budget at this time.

The glaze was mixed to a specific gravity of 1.45 - I noted on Glazy that this was recommended, but I feel that it was a touch too thick (perhaps I calculated the specific gravity inaccurately). 

I had another issue I have not encountered from a firing before - a brown patch on the bottom of one of my platters and a whiter spot on the glazed top surface.  I have attached a couple of images. This piece was placed on the bottom shelf and had 5cm/1.9 inch props between the next next shelf. Do you know what has caused this?

IMG_5992-1.jpg.c16b551ee42c0b05a8616860622977e2.jpgIMG_5991.jpg.bd97a703f9b6387eb2500dbe3e8e993f.jpg

 

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Glad the simple fix worked well with the 20X5!

Dipping glazes are typically in the 140 range.

Interesting in that the white spot almost appears to be another claybody or white underglaze just in this area.. It actually reminds me of bisque fix products on my porcelain but truly looks to be part of the claybody not the glaze. These are hand built I believe so I occasionally get clay with interesting things in it from the manufacture. In thrown construction it often gets mixed well enough to be nearly invisible. Just thinking here, no way to tell for sure from the pictures.

As to the small brown patch, any little contamination could be it. Brown clay, a bit of iron oxide that got in the body or transferred during loading from another pot or got in the glaze mix. We had a mystery bit of contamination with one of our artists that exclusively uses commercial glaze. Turns out she needed to screen the glaze, something refractory got in it at the factory or in the studio.

here is a simple  SPG refresher video we made for our students. It uses a 50 ml. syringe doubling the result (less accurate) but you can confirm your method with it. Basically measure out exactly 100ml of glaze in a tare weighted container and weigh it.

 

 

Edited by Bill Kielb

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Hi Bill,

Thank you for your help. I've just watched your video. I love the syringe idea! So much more tidy than pouring into a measuring cup. I will definitely purchase a syringe.

The white spot is exactly where the brown spot is on the other side of the dish, so I think it must be the same thing causing it. Could it be contamination in my kiln wash? I had applied new kiln wash on the shelves prior to bisquing but did not notice any issues until after this glaze firing.

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I think uneven heating/cooling is being reflected in the color variations top and bottom  - a broad, thin  surface in direct contact with the shelf only in that spot, vs the rest of the platter exposed on upper and lower surfaces. A little wadding might be called for.

or give the platters some "bubble feet."

Edited by Rae Reich

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11 minutes ago, Rae Reich said:

I think uneven heating/cooling is being reflected in the color variations top and bottom  - a broad, thin  surface in direct contact with the shelf only in that spot, vs the rest of the platter exposed on upper and lower surfaces. A little wadding might be called for.

or give the platters some "bubble feet."

Likely would have stuck to shelf if touching. I think its fully glazed 

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