I’m not a plaster master, so I don’t know if this is a good or even original idea. By mixing plaster in a plastic bag, it seems easier to remove bubbles from the mixture, while pouring is much more controlled. It’s the same idea as using a garden watering can for pouring glaze: You pour from the bottom where pressure is highest and bubbles are fewest.
In Chinese Glazes, we learn from Nigel Woods that the cobalt used for underglaze blue & white underglazes and blue glazes came in a range of chemical compositions and grades of purity. Thus, there are many shades of blue due to the quality of cobalt-containing stone as well the overlying glaze.
In the same book, Nigel presents a lovely Chinese blue stoneware glaze which, in addition to cobalt, contains iron and manganese “impurities”.
In fact I’m personally not fond at all of glazes and underglazes containing only cobalt as a coloring oxide. Pure cobalt often comes out as a garishly blue color. In the triaxial blend below, I take a nice clear glaze (Sue’s Clear) with added 1% Cobalt Carbonate. Then I blend with 1.5% Red Iron Oxide (bottom left) and 1.5% Manganese Dioxide (bottom right). The resulting colors on the bottom row are much more pleasing to my eye.
Out of these tests, there were two glazes that I preferred. The first, Sue McLeod’s Clear, is a soft clear with minimal clouding and has B2O3 at 0.18 which, according to Matt’s information, is ideal for cone 6 glazes.
The second glaze is a shop glaze available at the Wellsville Creative Arts Center called WCAC Celadon Clear. With B2O3 at 0.45, it is really high in boron and possibly less durable than the lower-boron clears I tested. However, WCAC Celadon Clear is by far the clearest glaze I’ve tested, almost like a layer of pure glass or honey. Even on dark stoneware it’s really clear with almost no clouding.
Being new to cone 6, I was curious as to the effect of boron levels on clear glazes. So, I created two biaxials, both with R2O fixed at 0.2. In the first Sue’s Clear inspired biaxial, B2O3 is set at 0.18. In the second biaxial inspired by Celadon Clear, B2O3 is doubled to 0.36.
Each biaxial resulted in a nice clear, with the higher Boron clear being almost completely transparent and glossy, while the Boron 0.18 clear is translucent and soft.
In order to test the effect of higher B2O3 levels, I doubled the amount of Boron in the initial biaxial from 0.18 to 0.36 while maintaining the same R2O:RO ratio. I also made the boundaries of the tests a little higher (see map comparison). I was surprised to see that the only clear glazes in the 0.36 Boron test appear much farther down (lower in Si & Al) in the chart. But the “clear” region is still in the same Si:Al Stull region.
After testing WCAC Celadon Clear and seeing the results of my B2O3 0.36 biaxial, it seems there is definitely a region of very glossy, very clear glazes at higher boron levels.
Coincidentally, I tested an old glaze recipe posted to the Clayart mailing list by Laura Speirs in 1996: https://glazy.org/recipes/21102 As with the WCAC Celadon Clear, the Speirs recipe is also very high in Boron (0.51), and it also fires very clear and glossy:
VC Easy Glossy
One afternoon I began discussing the WCAC Celadon Clear with a WCAC member, Nancy Alt. I was very surprised to discover the interesting history of this glaze.
In 2009 Nancy Alt had visited Val Cushing’s home and purchased a vase with a lovely blue-green celadon glaze. Nancy asked Val if he could share the glaze recipe, and he not only shared it but converted it from cone 9 to cone 6 (the temperature Nancy was firing). Val’s email is copied below. It shows the extremely generous nature of this amazing potter and teacher:
From: Val Cushing
Subject: Re: celedon glaze
Date: May 12, 2009 at 12:46:57 PM EDT
To: Nancy Alt
This glaze is one I made for C/9 oxidation electric firing, so that it would appear to be a blue green celadon. I have revised it for you to be the same color and texture only for C/6 ox. electric . I will give you two to try , first VC Pale Emerald, C/6 , glossy , blue/green , celadon looking. as follows………. Kona F/4 feldspar 24, Ferro Frit 3134 24, Dolomite 4, whiting 14, barium carbonate 2, zinc oxide 2, flint 24, and EPK 6. ADD TO THAT , 1/2 % COPPER CARBONATE for blue green. VC/easy glossy, C/6 ox. , electric , celadon looking , green. Cornwall Stone 46, Gerstley Borate 20, Ferro Frit 3124 26, Ball Clay 8. — add 2% copper carb. and 1/2 % red iron oxide for celadon looking green color. Test these two Nancy and if the color is not exactly what you expected let me know and we can make a revision. We may have different “tastes” about color , but we can get what you want…My pale emerald should be quite a bit like the glaze on the jar of mine you now have. and THANK YOU . Val
So it turns out that the glaze I liked so much, WCAC Celadon Clear, was actually a Val Cushing recipe called “Easy Glossy”. I checked Cushing’s Handbook for the recipe and didn’t find it. Nor could I find similar recipes in the Glazy database. So it’s quite possible this is a newly discovered Val Cushing glaze recipe.
However, the WCAC Celadon Clear had been modified from the original “Easy Glossy”, most notably subbing Gerstley Borate for Gillespie Borate. I wanted to see not only the original recipe but also the color variations that Cushing was working with. So I created a triaxial blend.
Below is the triaxial blend using Copper Carbonate and Red Iron Oxide.
Curated by Ursula Hargens, this exhibition will explore how place informs an artist’s body of work and highlights five artists—four Americans and one Canadian—who spent time in residence at influential ceramic centers around the world, or lived abroad for a significant time. Some of these artists launched their careers with this singular experience; others helped to build an institution’s notoriety and create opportunities for the next generation of makers; still others were part of a long lineage of experiential making in places steeped with history and making. The exhibition will showcase work created before, during, and after their experiences, demonstrating the impact of location on materials, process, culture, and concepts.
For the total work required to make a single cup, it must pass through 72 hands, and only then can it become a vessel.
72 Hands is an effort to document all types of ceramics techniques. The video style is very simple- a single take of each technique focusing on the artisan’s hands. Each video is accompanied by an article with a description of the technique and photos. Videos are shot in high-resolution 4K Ultra-HD resolution which gives a clear view of the technique.
Support 72 Hands
To support the continuation of this documentary series, please consider becoming a patron.
“From, In, to Jingdezhen; Eight Experiences”, an exhibition organized by Jae Won Lee, brought together a mix of artists who make work in Jingdezhen.
For this exhibition I refined the porcelain slipware that I began last year, exploring new designs with brushed slip. I also began a documentary project, 72 Hands (72hands.org), in which I am recording traditional craft techniques in high-definition video.
다양한 도자경험의 산실, 경덕진(景德鎭, Jingdezhen) 2017 클레이아크김해미술관 하반기 기획전『경덕진; 백자를 탐닉하다』는 아홉 명의 예술가(일곱 명의 도예가와 두 명의 협력자)가 제시하는 백자에 대한 여덟 가지 유형의 시각을 조명한다. 이들은 우연히 혹은 운명적으로 중국 전통도자의 수도인 경덕진을 접했으며 이곳을 자신들의 창조 작업과 활동의 본거지로 삼았다. 이곳 토박이인 왕 지안을 제외하면 이 전시에 참가하고 있는 도예가들은 도자 연구를 목적으로 경덕진을 처음 방문한 후 자주 이곳을 찾았거나, 여러 차례 장기간 체류하거나, 혹은 심지어 이주해 이곳을 자신들의 생활터로 삼은 경우도 있다.
19세기의 도자제작기법이 여전히 통용되고 있는 경덕진의 환경 속에서 이들 도예가들은 자신들의 다양한 배경, 예술적 목표, 습성, 문화, 언어, 철학, 전통에 기반해 새로운 것을 모색하고 발견하고자 했다. 도자제작의 중심지에서 일어나고 있는 정신과 물질의 상호관계와 변화는 독특한 도자작업, 다양성의 문제, 공동체라는 개념 그리고 역동적인 변화로 방문자들의 눈길을 붙잡았다.
이번 전시에서는 기(器, vessels)의 개념을 다양하게 보여주는 작품을 선보인다. 각각의 작품은 그릇의 개념을 직접적으로 다루고 있거나 간접적으로 이러한 주제를 구현하고 있다. 경덕진과 관련된 이러한 여덟 가지 유형의 패러다임을 통해 도예가들은 인간마음의 메레올로지(mereology, 부분과 전체 사이의 관계를 연구하는 학문)를 표현한다. 경덕진의 도자를 자신만의 독특하고 혁신적이며 비범한 결과물로 변화시킨 이들의 창조적인 작업과 삶에 경의를 표한다. 이들이 보여주는 여덟 가지 유형의 경험은 단순성, 문화적 표상, 혼합, 그리고 연금술적인 큰 뜻과 예술적 이상을 종합적으로 보여준다.