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Raku Clay + Clear Glaze Advice


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Hello all, 

 

I've just recently set up to do raku on my own.  I previously had a teacher when I was living in France.  Since I've been back in the states, I've had a very hard time finding a clay body and glaze comparable to hers.  Over the weekend, i fired 5 different types of clays that were sent to me in samples.  I tested two different clear glaze recipes, one of 70% greatly borate and 30% nepheline syenite, and the other was the 50% greatly, 20% syenite and 10% kaolin.  

 

I wasn't very happy with the results.  I found the clay body to be too grey, and dull looking.  I wasn't happy with the clear glaze results either.  A few had the start of a few nice large crackles, but most of them had too many small cracks, making the piece even duller.  It seems the large cracks didn't develop enough.

 

I'm wondering if I maybe did something wrong in the reduction or application of my glaze?  Could i have let it sit too long in the reduction chamber?  

 

My teacher used a pure white natural clay with very a very fine grog, with a clear glaze made of 90% frit and 10% kaolin.  I cannot find the frit she used anywhere in the states.  the brand is Ceradel Frit 1254.  Would anyone know of an equivalent?  I checked the compositions and compared to Ferro frits, but they are all missing an element or two. 

 

Would anyone know where I can get a nice fine grogged bright white body raku clay??

 

I'm still kind of new to this, and going at it on my own isn't easy, so if anyone has some suggestions they would be much appreciated.  I can send pics if that helps any.  

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since clay buying is sort of a local thing, where in the country are you?  there are east coast clays and west coast clays as well as middle of the country clays.  shipping and availability will matter so knowing where you are will help someone make a reasonable suggestion.

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to find an equivalent fit for Ceradel 1254, it is a Barium Zinc borosilicate frit. Info provided by Digitalfire.

 

Ceradel Frit C 1254 Barium zinc borosilicate frit

Alternate Names: Fritte C1254, Fritte C 1254, Ceradel Frit 1254

Oxide Analysis Formula BaO 4.30% 0.072 CaO 6.80% 0.313 K2O 0.60% 0.016 Na2O 10.20% 0.424 ZnO 5.50% 0.174 Al2O3 7.70% 0.195 B2O3 15.20% 0.563 SiO2 49.40% 2.120 Oxide Weight 257.15 Formula Weight 257.15 If this formula is not be unified correctly please contact us.  COLE - Co-efficient of Linear Expansion 72x10-7 (20/300C) GSPT - Frit Softening Point 800-920C
 

 

 

I found a few with Zinc and barium but with different percentages and melting pants, and COLE. You may have the time to go through these. It is an extensive list.

As Old Lady says, if we knew where you are located we could recommend suppliers to contact who may have the type of raku clay you want.

 

Marcia

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Thank you both!  I am in Austin, tx.  I've tried the raku clay they sell at our local clay supply and didn't like it at all.  They haven't been much help in helping me find anything.

 

I've also tried 5 different recommended clays from a supply store in Louisiana.  

 

Thanks, 

Laurene

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You've tried that many bodies and you aren't happy with any of them? What exactly is wrong with them- is it the color, texture, workability, etc?

 

80% Gerstely Borate + 20% Neph Sy is a classic raku clear crackle. But you could use any low fire clear and get the same results. 90% Ferro 3124 + 10% Kaolin is what many commercial low fire clear glazes are made from. The key to getting good big crackles with any of them is to apply the glaze thick. Too thin and you'll get small crackles. Also make sure it's fired hot enough. It should bubble up and then gloss over before it's pulled from the kiln.

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I find most clays sold as raku clay to be too groggy. I like Laguna's b-mix with grog because its pretty fine and is quite white at raku temperature.  It greys some in high fire.  Also clay planet has this smooth sculpture clay that rakus pretty nicely. Grey in the bag but fires up white. 

 

and we use the 80%gb  20% neph sy  with good results.  fire to cone 06.  We get these  free standing cones that don't need to be in a piece of clay to stand up. just need the one. works pretty well. Our raku kiln used to have hot and cold spots but is more even now since we got a better burner and refurbished it a bit.

 

the 80/20 basic clear crackle can also have mason stains mixed in or even be combined with commercial low fire glazes. just have to mix well. or use a low fire and put a coat of clear over it. 

 

To get plenty of crackle i let my pieces cool for a minute or so then mist them with a bit of water before going into the trash can.  Results vary but it seems to help get crackle.   Also make sure your glaze coat is thick enough to crackle.    rakuku

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The clays that I tried were either too groggy or I didn't like the color of them.  They were too grey-ish and dull looking once fired.   Workability-wise, I liked maybe 2 out of the 5.  I'm trying to find a result using only a clear frit, so the color of the clay matters.  

 

I'll try the 80% to 20% next time, and will try the Ferro frit.  I applied two coats of the glaze, will try three next time and see what that gives me.  I've heard about the Laguna B-mix being a good option for raku, will have to try it next.  

 

I've never tried misting them before putting them in the bins.... thanks for the tip! :)

 

Marcia, when will you be in Austin?  Are you doing any workshops?  Would love your advice since you're local! 

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If the fire ban is still in effect, we won't be firing. We are going to be running around on Friday if we don't fire. I want to see some galleries, visit Armadillo clay and Jerry;s Artarama.  Just firing with a friend. No workshop. PM me and I will give you my cell phone.

 

Marcia

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