Sometsuke: How Japan's Cobalt-Blue Porcelain Found Its Voice

In sometsuke (染付), cobalt-bearing pigment lies beneath a glaze. Firing turns the painted marks blue, giving Japan’s blue-and-white porcelain its outlines, washes and patterns. Look at how those marks meet the white ground, and how the design follows the vessel.

Gosu and the glaze

Sometsuke means underglaze-blue decoration and is especially familiar on porcelain, though the term is also used for pottery. The characters relate to dyeing and applying colour. Blue painted over an already fired glaze uses a different process.

The pigment is called gosu (呉須). Its fired appearance depends on the pigment recipe, body, glaze, application and firing conditions. Raw pigment often looks quite different from its finished blue.

Where Sometsuke Came From

Japanese porcelain began in the early seventeenth century with an important contribution from Korean potters. Arita’s history museum places the archaeological beginnings in the 1610s and distinguishes them from the founding tradition associated with Yi Sam-pyeong (李参平, Kanagae Sanbee). He is still honoured at Sueyama Shrine in Arita.

Early Japanese porcelain from the first half of the seventeenth century is known as Shoki-Imari (初期伊万里). Small, sparsely painted blue-and-white pieces for the domestic market belong to this early period of Japanese sometsuke.

The Arita–Imari–Hasami Corridor

Arita and Imari in Saga and Hasami in Nagasaki share a history within Hizen ceramics. Imari was an important shipping port, while production developed across several kiln areas. Their products, customers and division of work changed over time.

For regional context see Japan's Pottery Regions; for ceramic bodies see Stoneware vs Porcelain.

Historical traditions and familiar motifs

Ko-Imari: older Imari porcelain

Ko-Imari (古伊万里) is a broad name for older Imari porcelain, including blue-and-white made for domestic and export markets. Contemporary pieces may borrow its designs, as in this Ko-Imari-style lidded bowl; “style” describes the influence, not an antique date.

Nabeshima: porcelain for official gifts

Made under the Saga domain’s patronage, Nabeshima ware is known for carefully spaced designs, precise outlines and detailed feet. These features explain its appearance; attribution still requires evidence about the object.

Contemporary tableware and bells

Modern Arita and Hasami production ranges across tableware and decorative objects, with varied painting and forming methods. Compare the faceted sometsuke karakusa bowl and striped Arita fūrin for two uses of blue on white.

Karakusa: scrolling plants

Karakusa (唐草) is a scrolling plant motif found across materials and periods. On blue-and-white porcelain it may follow a rim or spread across a whole vessel, with white space separating the turns of the stems.

The Pine-Bamboo-Plum Vocabulary

Shōchikubai (松竹梅)—pine, bamboo and plum—is an auspicious grouping associated with endurance and renewal. Our Arita Sometsuke Shōchikubai Oval Platter offers one example. Other motifs include chrysanthemums, waves and cranes. Blue-and-white can feel visually refreshing at a summer table; see Japanese summer cooling and ryō o toru for the seasonal context.

Blue glass uses a different process

Cobalt can also colour glass, but blue Edo Kiriko is cut glass rather than sometsuke. Cutting through the outer coloured layer of cased glass reveals the layer beneath; painting pigment under a ceramic glaze produces blue-and-white porcelain.

Looking closely at sometsuke

Follow the painting around the form. These details help you appreciate the work; ask for a process description if hand-painting or another technique is important to your choice.

Lines

Notice changes in width and spacing, and where a line pauses or turns. Handwork can be very regular, while printing can reproduce irregular marks, so line variation alone is not proof of the method.

The blue

The pigment maker Fukaumi’s firing comparisons show how gosu recipes and firing conditions change the colour. A grey or uneven blue can be part of a chosen effect rather than faulty pigment or firing.

The white ground

Look at the contrast between blue and the body and glaze beneath it. A cool white, grey cast or warmer ground changes that relationship. The exposed foot offers another view of the body.

Dami washes

Dami (濃み) fills outlined areas with pigment from a loaded brush. Notice where colour pools, thins or meets the outline, and how that contributes to the whole pattern.

The relationship between blue, glaze and white space connects early sometsuke with contemporary work. Recipes and firing have changed, while makers continue to adapt familiar motifs.

Frequently Asked Questions

Why does the blue look slightly different on older vs. modern sometsuke?

Natural cobalt ores and modern recipes contain different proportions of colouring components. Body, glaze and firing also affect the result, so colour alone is not a reliable guide to age.

Can sometsuke be made on stoneware?

Yes. The Hatakeyama Museum’s account of Kenzan’s pottery includes sometsuke among his decorative methods. Our Stoneware vs Porcelain guide explains the separate question of the ceramic body.

Is sometsuke dishwasher and microwave safe?

Check the individual product’s instructions, decoration and condition. Cobalt in a fired colourant differs from an applied metallic gold or silver layer, but underglaze blue alone does not confirm appliance compatibility. See the Japanese porcelain care guide.

Editor's Note

This is volume 01 of Color of Utsuwa, our series on colour and surface in Japanese ceramics. Related studies explore hakuji white porcelain and celadon (seiji). For lacquerware, see Urushi Studies vol.01 — Wajima-nuri.