Nuka glaze too runny

[Drew]

Hi, I am in the process of testing a Nuka glaze (synthetic) and have found the results to be a little too runny at a cone 10 reduction firing. I would like to make it less runny without changing the glossiness of the glaze and make it more stable for a wood firing. Could anyone recommend some changes to the recipe please? Thanks in advance.

 

Silica 27

Nepheline Syenite 21

Mixed wood ash 20 (unwashed)

Whiting 11

Gillespie Borate 8

Talc 5

Bone Ash 5

Ball Clay 3

[liambesaw]

You can try washing the wood ash or changing some of the neph sy for Custer Feldspar, or trying it without the gerstley, this reads like it might be formulated for cone 6 or less so no wonder it's running so bad

[Bill Kielb]

2 hours ago, Drew said:

Hi, I am in the process of testing a Nuka glaze (synthetic) and have found the results to be a little too runny at a cone 10 reduction firing. I would like to make it less runny without changing the glossiness of the glaze and make it more stable for a wood firing. Could anyone recommend some changes to the recipe please? Thanks in advance.

 

Silica 27

Nepheline Syenite 21

Mixed wood ash 20 (unwashed)

Whiting 11

Gillespie Borate 8

Talc 5

Bone Ash 5

Ball Clay 3

Cone ten, why any boron?  (Gillespie borate)

[Min]

I would try replacing all the nepheline syenite with custer,  try placing the pots in a cooler part of the kiln. You could also try a line blend increasing the ball clay to reduce running but might loose some of the nuku qualities.

edit: I would also try a line blend where you are increasing the silica only. Also, what mesh silica are you using? 325? 

[neilestrick]

I'm with Bill. Boron shouldn't be needed in a cone 10 Nuka glaze. I would start by reducing the Gillespie Borate.

Another thought- I'm not a big fan of using real wood ash. It's a lot of work, the unwashed ash is fairly caustic, you won't necessarily get consistent results from batch to batch. This glaze has already strayed from a true Nuka in that it isn't using rice hull ash and has boron in it, so why not go all the way and formulate out the wood ash, too? Once you get it dialed in, you won't have to tweak it like when you get a new batch of ash.

[Min]

I believe the boron is in there because this recipe looks a lot like a tinkered version of the Phil Rogers fake Nuka glaze. Whiting cut in half and extra calcium supplied by wood ash then for the boron in 3134 replaced with gillespie borate and potash spar replaced with nepheline syenite is what I'm guessing was the thought behind it.

Phil Roger's Synthetic Nuka ^10
Potspar 35.6
Whiting 21.8
Talc 2
Bone Ash 2
Ball Clay 5.9
Flint 29.7
ferro3134 3

[liambesaw]

6 minutes ago, Min said:

I believe the boron is in there because this recipe looks a lot like a tinkered version of the Phil Rogers fake Nuka glaze. Whiting cut in half and extra calcium supplied by wood ash then for the boron in 3134 replaced with gillespie borate and potash spar replaced with nepheline syenite is what I'm guessing was the thought behind it.

Phil Roger's Synthetic Nuka ^10
Potspar 35.6
Whiting 21.8
Talc 2
Bone Ash 2
Ball Clay 5.9
Flint 29.7
ferro3134 3

So you think they reformulated for cone 6? Can't think of any other reason to sub neph sy for custer

[neilestrick]

1 minute ago, liambesaw said:

So you think they reformulated for cone 6? Can't think of any other reason to sub neph sy for custer

Maybe when Custer went goofy?

[neilestrick]

31 minutes ago, Min said:

I believe the boron is in there because this recipe looks a lot like a tinkered version of the Phil Rogers fake Nuka glaze. Whiting cut in half and extra calcium supplied by wood ash then for the boron in 3134 replaced with gillespie borate and potash spar replaced with nepheline syenite is what I'm guessing was the thought behind it.

Phil Roger's Synthetic Nuka ^10
Potspar 35.6
Whiting 21.8
Talc 2
Bone Ash 2
Ball Clay 5.9
Flint 29.7
ferro3134 3

Yes! No real wood ash to deal with, and more clay to help keep it suspended.

[Drew]

Hello everyone and thanks for your replies.

The recipe was from glazy (https://glazy.org/recipes/39479) and was for cone 8>10. I wanted to make a cone 10 Nuka but cannot source rice ash husk in New Zealand so tried this recipe. Looking at the Phil Rogers fake Nuka I may try that too. I have a wood firing in 6 weeks and am keen to use a nuka glaze on some of the pieces.

[Magnolia Mud Research]

My memory is that the Japanese Nuka glaze was a mixture of a lot of rice ash (silica), wood ash (calcium and potassium), and clay. The whiteness was from the unmelted rice ash.  

Starting from scratch, assuming that the Japanese Nuka glaze was basically rice ash, wood ash, and clay,  I would start with a common cone 10 celadon glaze and remove the iron and add say an additional 25 or 50% silica and see what happens in on a test piece a cone 10 reduction ( or electric) kiln firing.  The celadon I use has not run in either a gas or wood kiln firing and I expect that saturating the glaze with silica will make it stiffer, not runny.  
Custer    51 
Silica    22
Whiting    17
EPK    10
(all weight%)

Keep it simple.

LT

[Drew]

Here are the test tiles. The clay is a mixed buff and white stoneware clay with #40 grog. The tests were dipped to the run line. I was in the pottery today and unfortunately I cannot source Potspar to create the Phil Rogers Nuka, can anyone recommend a substitute. I did come across this Nuke recipe which I will test next week:

Nuka Cone 10 (ceramic arts handbook series)

Bone ash  2,
Talc 2,
Whiting 22
Wood ash (unwashed) or Frit 3134  3
Custer Feldspar 36
OM-4 Ball clay 6
Silica 30

Cheers

 

[Min]

Looks like there is a potash feldspar available from here in NewZealand.