Gansai is Japanese watercolor.It is made of pigments hardened with gum-arabic and glue（膠：NIKAWA.It is gelatin, and made by boiling animal’s bones, skin, and intestines, then drying and hardening them.) .
Kuretake (one of the Japanese supplier) sells not only Japan. One of their product series are named “Gansai-Tambi.”Tambi” means aesthetic.
Official site → https://www.gansaitambi.jp/en/
Gansai is similar to transparent watercolors.And Gansai is also similar to opaque watercolors. I feel that Gansai is somewhere between transparent and opaque watercolor.
Above pictures show color samples of Gansai and Transparent Watercolor(Holbein Artists’ Watercolors).
Almost colors are similar. Gansai has many variations of green.
Feeling of use
You can dissolve Gansai very easily. Because of possibility of overpaint, it tend to show opaque color.
I think you should dissolve it once on the palette, instead of putting the Gansai directly on the paper,
You can paint transparently by using a palette.
Characteristics of Gansai
Gansai has Japanese-style colors.
I explain two examples “Byaku-Gun()” and “Byaku-Roku()”. Byaku-Roku is blue with white,and Byaku-Roku is green with white.
Those two colors have same spell “Byaku”. it means white. White is commonly called “shiro” in Japanese, but the Chinese character for white (be writed “白”) can be read either “shiro” or “byaku in Japanese.
The white color gives it a softer hue. I think its hue reflect the Japanese climate (humidity and sunlight).
Gunjo（群青）is called “Gun”. Gunjo made from crushed azurite, a blue mineral, instead of lapis-lazuli. Gunjo is a very old Japanese color name.Traditionally, Japanese people have used iwa-enogu paints made from crushed minerals.（Of course, even today, some people use iwa-enogu to paint.）
Rokusho（緑青）is called “Roku”. Rokusho made from crushed malachite, a green mineral. Rokusho is also a very old Japanese color name.
Whiteness of these colors cause from their particle size, instead of their original material color. As it becomes finer and finer, it shows whitish in color. Particle fineness is showed by number. The smaller number means fine particle. However the finest particles are call “Byaku” especially. The name of “Byaku-Gun” and “Byaku-roku” come from this.
Enjoy your painting life♪