What is mugi urushi?

repairing a broken plate
Japanese craftwork used to be parsed out into incredibly specific micro-roles. The bristles of the drawing brush, used for hyper-detailed lacquerwork, is made from mice hairs. And not just any mice will do. It was said that the highest quality hairs for this particular purpose was that of ship mice. So there used to be a professional who catches the mice. Then there was the professional who removes the hairs. And another professional to wash and treat the hairs. And yet another to bind the hairs. And another to sell, and another to deliver. All before arriving to the professional who applies the bristles to the handle. And we mustn't forget about the host of professionals who are at the end of that handle too. 
The structure of micro-roles is not just reserved for toolmaking, but it certainly applies to the processing of materials as well. So it isn't a surprise that there used to be a professional who spent their life refining the craft of mugi-urushi making.
Mugi urushi or wheat urushi serves as the sticky glue that binds completely broken pieces together. While you could technically use any adhesive bond like epoxy, cashew resin, or other synthetic glue, there are several reasons why we opt for flour and urushi instead.
Concerns of synthetic glues:
  • Not a food-safe repair
  • Fragile repair and may break again easily
Benefits of synthetic glues:
  • Easy access
  • Quick drying time
  • Low skin irritation
Concerns of mugi urushi:
Benefits of mugi urushi:
While synthetic glues lie on the surface of the breakage, urushi tree sap finds its way deep into the pores of the ceramic or porcelain ware, becoming one with the clay or stone that was originally used before going into the kiln. This is why traditional kintsugi repairs are so durable. The chemistry of like attracting like, rings true in authentic urushi-based repairs. Rather than relying on binding two broken pieces together by sandwiching a single layer of glue, urushi serves as microscopic hooks that pull the broken pieces together from deep within each part.
In our instructional leaflets and how-to Master Class videos, we suggest white wheat flour to make mugi urushi, as it is the most simple recipe and is very much enough for basic repairs. A quick note however, that regular white rice flour and white mochi rice flour are often used as well. White wheat flour gives mugi urushi its glutenous viscosity, and rice flour adds to make for an even stronger and more durable hold. More on rice flours in a future entry.

Mugi Urushi Recipe

  • Flour (white wheat flour)
  • Water
  • Kiurushi (raw urushi)
  • Small spatula
  • Glass palette or ceramic tile
  • Dropper
  1. With the spatula, scoop up a small amount of flour and place on a palette. How much? Enough so that a thin layer of mugi urushi can be laid onto both surfaces of the broken piece. If you do not have a palette, simply use a glazed ceramic, porcelain, or glass plate instead. 
  2. Use a dropper to add water to the flour, one droplet at a time, and use the spatula to knead as you go. Essentially, you are making dough. Not as hard as pasta dough or as loose as pancake batter, but somewhere between cookie batter and bread dough. 




  3. Once you think you've gotten to a good consistency, right next to the dough squeeze out an equal amount* of kiurushi as the flour. Begin by kneading in half of the kiurushi. Once it's combined, add in the second half. You are looking to create a consistency similar to that of chewing gum. When you pull the spatula from the palette, the mixture should stretch quite a bit. 





  4. Take the spatula or bamboo palette knife and lay a very thin, even layer of mugi urushi to both surfaces of the broken piece.



  5. Prepare several pieces of masking tape.
  6. Push the broken pieces together, sliding and nudging them a bit until you feel like they have clicked into place. 



  7. Begin pulling the pieces closer together by leveraging the slightly elastic nature of the masking tape. Tape both the top (inside) and bottom (outside) of the broken ware. The pieces should be very tightly bound. 



  8. This is the perfect time to double check whether the two pieces are level with one another. Take a pen, knife, or other firm tool and rock it back and forth between the two pieces at several points of the bind. At least at the lips of the ware and in the center of the breakage. If you feel a little bump or step, then carefully peel the masking tape that's holding that specific area together and jiggle the pieces until they are level before securing with masking tape again.
  9. Place the ware in the muro in a way that leverages gravity instead of working against it. For example, if it's a bowl that's broken in half, rather than placing the bowl flat into the muro, like you would when placing in the cabinet or on the dining table, place it on its side so that gravity can help the pieces bind together. If it moves about, the bowl can be secured in place by using masking tape between the bowl and the walls of the muro. 
Happy repairing!
*In kintsugi repair, we never speak about a specific amount of any ingredient as it very much depends on the size of breakage, so we always speak in ratios.

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