Shino Glazes

Background

Shino glazes are a high feldspar glaze from Japan. Shino wares were made in Mino (present-day Gifu Prefecture) during the Azuchi-Momoyama Era. Shino was lost and then later rediscovered by Arakawa Toyozo in the mid 20th century. Arakawa popularized a new style of shino glazes from which modern shinos are derived.

Azuchi-Momoyama

• The original shino pots had quite muted red colors.
  • Some pots from this era are completely white.
• Pots are either hand built or altered and do not have very round shapes.
• Appraiser Nakajima Seinosuke analyzed the shino tea bowl Hirosawa for the anime Hyougemono

Arakawa

Arakawa Toyozo revived shino style pots beginning in the 1930's. The story goes that shino ware was thought to be from Seto, but Arakawa noticed red clay on the foot of a shino pot, which is not from the area. He knew that there was red clay in Gifu, his home prefecture, and later discovered shino shards at a ruin kiln site. Arakawa recreated the Momyama shinos and then created his own style of shino. For his work in shino and other Mino pottery, Arakawa was deemed a national living treasure.

I cannot find a good source for the above story because of the limited writings on Arakawa Toyozo and my limited Japanese reading ability.

• Modern Japanese shinos derive from Arakawa's style.
  • Arakawa's work has considerably more red color
  • Modern shinos also have more crawling.
  • Modern Japanese shinos differ from potter to potter
    • The commonality is that the glaze is primarily feldspar
  • Arakawa and modern shinos seem whiter than Momoyama shinos (which are slightly yellow or gray) - this may be due to modern mining and ore refinement producing lower amounts of iron and titanium
• Arakawa Shino Chousen kara Souzou he - CTK (Japanese)
  • Video by the Arakawa Toyozo Museum introducing Arakawa's work

A house with shino glazed wall tiles in Tajimi, Gifu, Japan. Taken March 2023.

American

Malcolm Davis was an American potter who brought shino glazes to North America and developed his own style.

アメリカの陶芸でも、志野は人気が高いといわれる。 しかし、日本人の持つ志野のイメージとはちょっと違って 白くてカイラギが出れば良いとか、白くて鉄が浸み出せば良いという感じらしい。 微妙な透明感や、質感などはあまり追求されないという。

I've heard that Shino is popular in American pottery. However, they're somewhat different from the Japanese idea of shino. It looks like whiteness, crawling, and the bleeding of iron color is important. It seems qualities like subtle translucency and texture aren't sought after.

- Kumatani Pottery Supply Blog

Traditionally, Malcolm Davis' shinos are formulated for high fire (cone 10 and hotter). These glazes do not melt enough at cone 6 and there has been little research into developing shinos for midfire. This may be because few potters fire in cone 6 reduction and may be because people falsely believe that shinos are not possible in midfire temperatures.

• The glaze is red to creamy yellow, depending on thickness
  • Davis' shinos are applied much thinner than Japanese shinos
• The pots can have Carbon Trapping due to the high amount of Soda Ash
  • Wax resist is drawn on the surface while the glaze is drying to draw designs in the carbon trap

Style Comparison

Form

Glaze

Qualities

• White
  • Underfired - Glass development is low. I believe the white, pearly color is caused by small unmelted particles scattering light. May be similar to porcelain translucency.
    • Evidence: Pure soda feldspar is translucent, but adding kaolin (which is refractory) increases the opacity
    • May also be caused by undissolved alumina particles. Some shinos have calcined alumina as a major ingredient.
• Matte texture
  • High alumina content - Most shino glazes I've seen are not very glossy. Shinos are known to be alumina mattes (as opposed to silica, magnesium, strontium etc. mattes).
    • Shinos are supposed to be high feldspar glazes, but American feldspars are high in silica, making them glossy, rather than high in alumina.
• Oranges and Reds
  • Iron wash - Japanese potters brush some source of iron over or under shino glazes. It may be high iron clay (like terracotta or Yellow Ochre) or iron oxides.
  • Alkali Flashing - Malcom Davis' shinos can be bright orange or red. Since the glaze is 1) low in iron, 2) high in clay content, 3) high in soda ash, the reaction is likely the same one that causes white stoneware to flash red in soda firing.
    • This would also explain why shinos have no RO flux (calcium, magnesium, etc.) - these fluxes suppress flashing
• Black
  • Carbon trap - When glazes high in Soda Ash are fired in heavy reduction, molten soda can dissolve carbon soot into the glaze. Shino glazes tend to turn black due to their high soda content.
  • Carbon trapping is rare among Japanese shinos, but is rather common in America

Raw Glaze Properties

Pinholes

The pinholes in the glaze are not created during firing. Feldspar melts very late and does not seal the surface until well after gases in the body and glaze are burnt off.

The pinholes are actually made when the water in the glaze is absorbed into the coarse body. Burnished surfaces do not pinhole while trimmed surfaces do. This is how it is possible to not have pinholes and crawling on the inside, which makes a usable surface.

Crawling

Both American and Japanese shino glazes can crawl. Crawling can be achieved by using a glaze with high clay content (> 30% clay), over flocculating the glaze with an excess of Epsom Salts, or both.

Thickness

The authors of Yakimonodzukuri, 100 no Shippai recommend shino glazes to be mixed to 60 degrees or higher on the Baume scale. If using a conversion factor of 144.3, this is equivalent to a Specific Gravity of 1.7 or higher. This is an extremely thick glaze, bordering on slip.

Hayashi Shoutaro has two shino glazes of the same recipe but different water content. The thinner glaze is applied as a base coat (which flashes red) and then the thicker glaze is poured over some areas on top (while the base is still wet). The second glaze is white and crawls because of its thickness.

Firing Methods

Japanese potters use wood fire kilns, but place work in saggars to prevent the buildup of wood ash on the surface of pots.

• Arakawa Shino Chousen kara Souzou he notes that Arakawa Toyozo lined the insides of his saggars with iron clay to promote flashing and the development of red colors.
• Ando Hidetake is seen firing his pots in saggars in Hono de Someru - Ando Hidetake

American shino glazes can have spots of black known as Carbon Trapping. The carbon trapping is created by the crystallization of Soda Ash on the surface of the dried glaze. The kiln is fired in strong reduction starting around 800C, when the soda ash begins to melt. Soot from the reduction is absorbed into the melting glaze, creating the black color. The kiln must be kept in reduction for the rest of the firing or else the soot will burn off.

North American Shinos

Malcolm Davis Shino

This is the shino from which North American recipes are derived. Davis' shino is quite different from Japanese recipes and is quite interesting in its own right.

There are two versions: the one with added Redart is for use with porcelain clay.

• The firing temperature is cone 10.
• Over 35% of the non-soluble ingredients is clay. This leads to heavy crawling if applied thick. To reduce crawling, calcine half of the kaolin and ball clay.

Tony Hansen's Shino

From the shino page on DigitalFire:

This is similar in spirit to Malcom Davis' shinos. Firing temperature is cone 10.

Additionally, here are Tony's guidelines on shino glazes:

• High percentage of Nepheline Syenite
• High amount of alumina (over 1.6 molar on the UMF), Silica-Alumina Ratio of less than 5:1
• Ball clay or kaolin to suspend the glaze
• Small amount of iron-bearing clay
• Small to significant amounts of tin (possibly to make Shinos work in oxidation)
• Boron source, lithium, or even zinc to reduce melting temperature
  • However, these seem to negatively affect the appearance and surface texture
  • Potentially used to reduce crazing

Japanese Shinos

Sodium / Potassium Feldspar

There are a lot of shino glazes that are 90-100% Feldspar. The difficulty is that the melting properties are dependent on the mining company. The physical processing and grinding alters the melting properties of the feldspar, so it may be near impossible to substitute ingredients.

Potters also talk about using "weathered soda" (風化ソーダ) as an ingredient. I have no idea what this is. Perhaps it's short for "weathered soda feldspar"? Maybe this refers to soda feldspar that has been chemically weathered and thus contains primary clay.

Hayashi Shoutaro says his glaze is 95% feldspar, 5% clay.

Hiratsu Feldspar

Touruji's shino recipe is 100% Hiratsu Feldspar.

Chemical analysis from Tougei Shop. Note that chemical substitutes are unlikely to have the same appearance as shino glazes are not well melted: they are highly sensitive to the physical properties of the material particles.

Firing schedule

• Slow ramp, around 15-17C/hour
• Start reduction at 900C
• Peak temperature of 1200C (takes 2-3 days with a wood fired kiln)
• Slow cool to 900C, around 10-12C/hour
• Hold at 900C for one day
• Cool in reduction

This glaze requires a clay body with 1-1.5% Fe2O3.

Petalite

Majita of Andon's opinion on petalite is that petalite glazes are "Shino-like", not "true" shino because the Alkali Flashing is not as strong. It is a "sleepy hiiro", neither red nor purple.

Sintered Alumina Shino

There are also shino recipes that are not mainly feldspar but contain a large amount of alumina.

This recipe is from Yakimono no Kagaku by Higuchi Wakana:

• 3.7 is a very high amount of bentonite. This glaze will be extremely thick.
• Why is there 0.8% whiting?
  • Maybe to control the amount of alumina dissolved into the glaze

Firing schedule

• Ramp for 16-18 hours to peak temperature (about 60C/hr ramp)
• Start reduction at 945C, end at 1150.
• From 1150C to peak temperature of 1210-1230C, alternate between neutral and reduction
• Hold for 15-30 minutes at peak temperature

Created 2024-02-09. Updated 2024-03-25.

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