Traditional Mokuhanga Pigment Mixing: Using a Wooden ‘Mortar and Pestle’

pigment drawer
The pigment drawer at Mokuhankan– Asakusa, Toyko

I had the pleasure of spending a month working at Mokuhankan Studio in Asakusa, Tokyo from May to June, 2017. One of many new experiences for me was, under the direction of Natsuki Suga (who worked under Kenichi Kubota at the Adachi Institute for 5 years) to make relatively large batches of color using wood board mortars and pestles. This is to assure the pigments’ quality and to create a well-mixed supply of color paste that is ready to use later. Each color requires it’s own sanded cherry board and pestle (pine with cherry faced using epoxy glue) that was made by Lee-san.

Cherry blocks made by Lee-san to be used as a pigment griding ‘mortar and pestle’.

Like most printers, I generally use a mortar and pestle for a far too short of a time in order to grind pigments into a paste [for beginning printers, this resulting color paste is then later added by the printer to the block with varying degrees of water and nori (starch) paste while printing]. For the record, I’m pretty slack and sometimes just mix the pigment out of the bag with water (sometimes w /alcohol to break the surface tension) using only a brush/tokibo or hakobi. I am learning that mixing the colors thoroughly helps create much smoother colors and avoids a print being spoiled because of stain blotches which sometimes show up during printing from not mixing the pigments well enough.

“Warning: It takes a long time.”

This process of grinding on a board takes a long time but, unlike using a deep mortar, you can much more easily see the texture of the pigment on the flat surface.

List of colors:

A list of colors used at the Mokuhankan printshop
Taking care not to spill pigments

Prep: Of the 5 colors, only bengara had pure ethyl (grain) alcohol added, mixed in the night before, and was allowed to sit open for the alcohol to evaporate. Also, pigments like bengara require more time to grind because the particles are coarser. You will need a wooden board, wooden pestle, a scraper (my credit card seemed to work well since it was not hard enough to damage the wood), water, jars.

Process:

(1) Wearing a mask, add a small amount of clear (preferably distilled) water to the dry pigments in a jar and stir.

(2) Approx. one tablespoon of damp pigment is then placed onto the top of the block.

The wooden pestle should be held at a slight angle as it’s pushed  towards the pigment.

(3) The wooden pestle is held at a slight angle away from the pigment to be ground and pushed with moderate pressure back and forth.

4) The processed portion naturally accumulates and builds up on the pestle which is then scraped off.

(5) Water is occasionally added, but Suga-san explained that too much water doesn’t allow the particles to grind against each other.

(6) After each pass, the color is then pushed back and the process is started over.

(7) The idea is to grind 4>6 times into a paste (refer to chart above it took on the average 45min. to process a tablespoon of dampened pigment). Suga-san said that the final surface should appear creamy-smooth.

(8) At the end of the grinding process, water is spread around and the residual pigment is gathered up.

Forcing the mulled pigments though a screen before storing

(9) After grinding, enough water is added to the paste to be pushed through a fine sieve into jars.

(10) Water is then very carefully added to the top. Over time, the water and heavier pigment naturally separate.and stored out of the light in a cool area of the studio.

(11) Each morning, the water is drained carefully off the top. New water is then carefully added again to the top of the drained paste after it’s used and returned to a cool, dark area. This process or replacing the water reportedly keeps spoilage down (presumably, by limiting exposure to air) as opposed to adding preservatives. The key is or course, not to shake or stir the jars.

Letting pigments settle
  • Additional references: Preparing powdered pigments can be found in a “Tools and Materials” section David Bull’s www.woodblock.com Encyclopedia article. The idea of keeping a selection of pigments stored in ‘paste’ form in an alcohol/water mix is discussed in ‘One-Point Lesson’ #6 in another section of the Encyclopedia.

NOTES AND OBSERVATIONS:

Mokuhankan is planning to compare this traditional method of grinding pigments with using a western-style glass muller/ glass slab combination. I suspect that this will result in less hard-won pigment being lost and may go a bit faster.

As of several days later, both the Ultramarine and the Indigo did not separate to clear water. I was a little suprised at the Ultramarine since it is a mineral pigment.

I’m also not quite sure that the step of pushing the pigment through the sieve is necessary since the ground particles are much finer than the screen.

After printing, mixing bowls are left to dry around the printing desks and are reconstituted (unless starch paste had been added) by simply adding a little water and stirring with the tokibo without apparent problems. I’ve noticed that this reconstituting doesn’t work as well with commercial tube watercolors since there is gum added and it results in a grainy texture.

“Pigmento Party” 2017! John, Suga-san, Aiyumi-san at Mokuhankan

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