Mica: Ukiyo-e colorant

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The Heron Maiden by Kitagawa Utamaro I

Mica 雲母 (kira or unmo): A group of silicate minerals that cleave into thin, flexible sheets. It is ground into a powder for use on prints. Powdered mica can be printed or sprinkled to create a shimmering effect. Starch paste or animal glue (膠 nikawa) is often used to affix the mica to the surface of the paper. It is a pearlescent white but can also be mixed with a colorant to make colored mica. Mica can appear in a variety of tones depending on its origin, preparation or if it is applied over a printed color. Pink, mica and a red colorant or dark gray, mica and carbon black are the most common tones.

Mica appears most frequently on prints made during the late 18th century that depicted actors and beautiful women where it was used on the background to highlight the figure. It can get easily abraded and also absorb moisture causing discoloration or dissolution.

For more information see: Mica

Examples of Mica in Ukiyo-e Prints

11.14364-pt9-detail.png

1114364-Pt9-XRF.jpg
Pt 9: printed or hand applied
Kitagawa Utamaro I, 11.14364

11.14673-pt6-detail.png

1114673-Pt6-XRF.jpg
Pt 6: printed or hand applied
Tōshūsai Sharaku, 11.14673

34.269a-b-pt11-detail.png

Indigo FORS.JPG
Pt 11: printed or hand applied
Kitagawa Utamaro I, 34.269a-b

11.15095-pt4-detail.png

Indigo FORS.JPG
Pt 4: printed or hand applied
Utagawa Kunisada I, 11.15095

Analysis

The presence of mica is best identified visually and with the aid of an optical microscope, via the observation of sparkly particles on the print. When present, mica can often be verified with X-ray fluorescence analysis (XRF). However, the major elements in mica (silicon and aluminum) have low atomic weights and thus produce proportionately small peaks because they occur in a region where the detector has low sensitivity. Trace amounts of additional elements (such as potassium, iron, manganese, titanium, chromium, barium, arsenic) can be present in the mica structure, or from companion minerals. Thus it is important not to attribute these elements as evidence of other colorants.

Images of Mica

List of Prints

Below is a list of prints where mica was detected.