This time in PIGMENT ARTICLE, we particularly focused on the “water-based” medium and asked chief Iwaizumi about its character.

Various kinds of medium with different colors and shapes are arranged on the table. What is the difference?

―In the previous article “PIGMENT Chief Iwaizumi Talks About the Medium and Its Character vol.1”, we talked about medium in general. This time, we would like to talk about the medium, with a focus on a “water-based” medium.

So, what is the oldest medium among the water-based medium?

Well, the oldest medium would be animal glue, which is because there is a record that the jellied broth from animals was used in Lascaux mural painting to stick the pigments onto the wall. It might be misleading to call them as animal glue, but if you consider them as medium that is made from “animal”, animal glue is the oldest water-based medium.

―Is this plate animal glue as well?

This is called “Plate glue”, which is the animal glue before processed into a liquid state.

―Is this plate animal glue as well?

This is called “Plate glue”, which is the animal glue before processed into a liquid state.

―How is it made?

It is made by drying and solidifying the jellied broth taken from simmering bones, meat, or vegetables. I will talk about animal glue in the next article.

―What is the egg used for?

In western countries, people used egg as a medium for tempera painting.

This is because the egg can be blended with oil, as you might know from the familiar example, mayonnaise. Of course, they used linseed oil that is suitable for painting and use it as a medium by mixing it with egg yolk. In western countries, egg was most commonly used medium before the invention of oil paints.

―Is the white powder also a similar kind of water-based medium?

This is called casein, which is a milk-derived protein. It becomes clouded medium when dissolved by ammonia. In the past, there is no powdered casein, so people grain cheese and use them as medium. From there, casein is also called “cheese animal glue”.

―I have the image that it is a technique to paint by permeating on wall when the ground is half dry.

Actually, the early fresco painting was painted directly onto the plaster with casein. However, people realized it had a problem in durability so this is when the fresco painting style was developed. Still, this technique did not allow making a correction, so casein continued to be used as an after medium for fresco paintings.

―What is this brown chuck?

This is the ingredient of Gum Arabic, which is taken from acacia tree. If you grind and soak them in water, it is naturally dissolved and you can create the liquid Gum Arabic.

Compared to the animal glue, Gum Arabic has a relatively short story and it was brought from Southeastern Asia to Europe after the Age of Discovery.

It is mainly used as a medium for watercolors. As you can tell from the fact that you can color by putting wetted brushes onto solid watercolor paints, the redissolution ability is the best character of Gum Arabic.

―Lastly, what is this white liquid?

This is the acrylic emulsion, which is a medium for acrylic paints. The acrylic resin, an ingredient of acrylic emulsion, is originally oil-based, so it requires some solvent to make it into liquid. Then, by adding the surfactant that connects oil and water, it becomes a water-based medium. The reason why acrylic paints become waterproof when it gets dried is because the water inside of the medium evaporates and the oil remains on the canvas. Such structure is similar to the tempera medium, and the acrylic emulsion is the scientifically reproduction of it.

―I see. There are many types of water-based paints.

Indeed. Furthermore, there is further segmentation in acrylic medium such as acrylic thickener to control the brush and medium to add texture to your painting.

―So, various expressions can be made by adding thickener and other medium to acrylic emulsion, does it?

Yes. There are samples of medium in PIGMENT TOKYO. Please take a look at it when you have a chance to visit our store.

商品紹介

OX glue liquid 20％ concentrated

https://pigment.tokyo/en/products/3060

Egg Tempera Medium

https://pigment.tokyo/en/products/3176

Casein Medium

https://pigment.tokyo/en/products/3175

Gum Arabic Medium

https://pigment.tokyo/en/products/3650

Acrylic Emulsion

https://pigment.tokyo/en/products/1218

Acrylic Thickener

https://pigment.tokyo/en/products/1217