Urushi FAQs

Where can I buy urushi? 

Various kinds of urushi and materials are available in small quantities from Nosaku in Kanazawa.

You need to be very specific about the type of urushi you would like and the drying speed. Please note that all urushi is adjusted to fit in with the Japanese climate and I would recommend buying fast-drying urushi and a tube of extra slow-drying urushi as well so that you can adjust the drying speed to your own personal environment.

What kinds of urushi are there ?

Urushi is mainly divided into three categories:

Ki-urushi which is an opaque beige colour, is the strained, unprocessed tree sap. The urushi gathered in spring ( hatsu-hen ) has a high water content as the trees pull up water from their roots for growth and is perfect for the ro-iro polishing process. The urushi tapped in autumn ( oso-hen ) is of poorer quality and so is used for the undercoats and sealing.  

Naka-nuri urushi is high quality urushi which has been harvested in summer ( sakari-hen )  Ki-urushi is continually stirred in large vats under a heater or by hand on a hot day. This is to evaporate some of the water content which thickens the  urushi for the first coats of pure urushi after the undercoats of shitaji are finished.

Uwa-nuri urushi is the urushi which is tapped in summer and is the best quality as it has the least water content and the highest amount of urushiol. This is the same as naka-nuri urushi but is stirred in the vats for a longer period until it becomes clear and has a honey like consistency. If all the water content is removed however the urushi will not dry so this process has to be carefully monitored and as urushi is a natural tree sap, the conditions and quality will differ each year with the trees and the climate.

Why is the same urushi called by different names?

Throughout history there have been many important lacquering centres in Japan and each area calls its urushi and process by a different name so it can be very confusing when talking to craftsmen from different areas like Tokyo, Kyoto and Wajima.

How do I dry urushi?

Because urushi contains a compound called urushiol which reacts with oxygen and hardens through a process of oxidative polymerization, it needs a stable condition of 60%~80% humidity and a temperature of 20C~ 25C to set. To facilitate these conditions, large wooden drying cupboards are used where the drying conditions can be controlled in a dust free environment. The drying process  proceeds gradually over a considerable length of time but if the conditions are not right, the urushi will either fail to harden or dry too quickly causing the surface in immediate contact with the air to dry first causing a skin to form which prevents the underlying urushi to oxidize and causes a wrinkling effect like a dried prune. The colour will also change after drying, going slightly darker than when applied.

How long does urushi take to dry ?

Urushi takes at least 24 hours to dry before it is possible to do the next stage. In winter when the humidity and temperature is low, it can take even longer. If urushi hasn’t begun to dry within 48 hours though, there is something wrong and it is best to remove it and start again. Final coats of Japanese urushi can take 14 days before they can be touched and although the surface may be dry, it is still too soft to be handled without risk of damaging the new coat. It takes a full year to really harden into the durable lacquerware that lasts for decades.

How do I make coloured urushi?

To make coloured urushi you need to blend pigments into clear uwa-nuri urushi.

I use the word “clear” but urushi is naturally brown so that it is impossible to get a really white finish.The nearest that is possible would be a light beige. The amount of pigment required varies according to the brand but the rule of thumb is as little as possible to obtain the desired colour. Pigments are an impurity and too much pigment will compromise the strength of the lacquerware when finished. Using coloured urushi with a high pigment content to tint maki-e work is more acceptable as the maki-e is then polished using many layers of high quality urushi which restores its durability.

Black urushi can be bought and is mixed with an iron compound to turn the urushi black. It is possible to add carbon to clear urushi to get a deeper black for the naka-urushi stage but this not recommended for final coating.

How do I strain urushi ?

For straining urushi mixed with rice glue or jinoko we use cotton fabric, wrapping the mix in the fabric and twisting it so that the urushi comes through the weave. For pure urushi, we use numerous sheets of washi or nylon paper. There are two ways to strain, one is to slowly twist the paper bundle so that the urushi seeps through or to pour the urushi into a box with a sieve made of numerous sheets of washi and leave to naturally drip though. The second method takes a long time and is usually reserved for the final uwu-nuri coats.

How do I remove urushi from brushes?

As urushi does not mix with water and paint thinners damage the delicate brushes, we use salad oil to wash out brushes. As oil stops urushi from drying, please be careful to remove all traces of oil from the brush when using it again.

How can I tell the difference between authentic Wajima-nuri and imitations?

This is hard as many objects have the same finishing coat but price is a very good indicator and enquiring about the production process is another. If the substrate isn’t wooden and hasn’t been reinforced with fabric or had the layers of jinoko undercoats, then it isn’t the real McCoy. This doesn’t mean that other products aren’t good or sturdy but they won’t live up to the durability of authentic Wajima-nuri or support the craft from disappearing.

What is the difference between Japanese and Chinese urushi?

Urushi used in Japan contains a chemical compound called urushiol which is responsible for hardening urushi and its lustre. In domestically produced urushi the urushiol content is higher which makes it stronger. This doesn’t mean that Chinese urushi trees don’t produce the same quality of urushi but in China they mix all the urushi tapped together, blending poor quality with excellent quality without regard to seasonal variations whereas in Japan, it is divided by area and season so it is easier to control the quality.