Saturday, October 17, 2015

Crystalline Glaze with Nickel Blue



I opened the kiln a couple of days ago and was delighted to see these glaze tests smiling back at me! It was especially good to see them as almost nothing else had worked as it should in that firing, so the little tests were needed to give me the encouragement to keep going!

These are tests of crystalline glazes with a little Nickel oxide added to colour them. Nickel can behave in a very interesting way in crystalline glazes in that it can give two colours from the one metal. The crystals are likely to be blue, and the surrounding glaze could be yellow, orange, or green!












The two glaze tests on the left of this photo were the same glaze recipe fired at different temperature. It is amazing to see the transformation that a mere 55 Celsius (131 F) has made! The first test (from an earlier firing) was fired at cone 7 (approximately 1230 Celsius (2246 F)) this has given a satin matt glaze; the second test was fired at cone 10 (approximately 1285 Celsius (2345 F)), and has dramatically changed to a shiny glaze with large crystals.

For those who might be interested, here are the glaze recipes used....

From the left, tests 1 and 2
use a Janet DeBoos Recipe (number 84 in her second book of glazes)
Potash Feldspar 35
Whiting  12
Zinc oxide 24
Silica 22
China Clay 5
+1.5 Nickel oxide

The three other tests use my base (which is slowly evolving)
Fritt 4110  (3110 in some countries) 47
Zinc oxide 27
Silica  24
Bentonite 2
China Clay 0.5

Test 3 (The center test) has + 2 Nickel oxide
Test 4 has + 1 Nickel oxide
Test 5 has + 1 Nickel oxide, 4 Manganese dioxide.

I fired this kiln manually and used cones for top temperature.
The firing took about 9.5 hours to cone 10
40 minutes to fall to about 1100 C (2012 F)
Hold for 4 hours.
Kiln off.

Note: I made several changes to the hold temperature to encourage growth rings to form in the crystals. I find a sudden drop of about 40 C (104F) from the holding temperature, a 5 minute hold, then a quick rise to the original holding temperature gives nice growth rings.

13 comments:

smartcat said...

Your crystal tests are other-worldly!
You make it sound so simple and I no for a fact it isn't!
More please!

gz said...

Now that WAS worth the work!

srgb said...

Just beautiful Peter its obviously dedication.

Arkansas Patti said...

Wow, you are a master. Just beautiful.

Melissa Rohrer said...

Beautiful. Satellite image of the earth?

Anna said...

Heard the saying, "Fickle Nickle" :) those are wonderful results... I'm still learning the varies of my own kiln and don't have to courage yet to try crystalline. Yours are terrific and generous of you to show the glaze recipes too.

Linda Starr said...

crystal blue persuasion

Michèle Hastings said...

those are very cool!

Peter said...

Dear All,
Thank you so much for your encouraging comments. All a busy whirl here, with one stoneware firing through the night finishing 9.30am today, instead of around 5.30am due to kiln problems. Now firing a crystalline glaze firing with the other electric kiln that is due to finish around midnight. Exhibition deadline is looming very close!! Must go and check the kiln, I'm currently busy putting growth rings into crystals by doing controlled dips in temperature. Best Wishes, P

Jordan said...

Absolutely stunning results. One looks almost like carved lapis lazuli, the other like a planet! I love it!

Peter said...

Thank you Jordan for the enthusiastic comment, it is good to hear from you. Another crystalline glaze firing happening as I write, hopefully have some green crystals in this firing...

Kees Staps said...

Hello Peter
Have you tried bentonite instead of clay in crystalline glazes and I found that firing the Janet de Boos to cone 9 gave good results raw glazed and fired with used vegetable oil heated in old hotwater tank and would love to send picture but how to attach pictures
Kees from yatteyattahpottery@gmail.com

Peter said...

Hi Kees,
Thank you for your comment, it is good to hear from you. I often use 1 or 2 percent bentonite with crystalline glazes to make them less difficult to apply, and to help them behave better in the glaze bucket! Generally I use little or no other clay. I would love to see your results, and am impressed that you are firing with vegetable oil, I have emailed you directly so that you can reply with photos.

Looking forward to seeing your work,

Peter