DISCLAIMER
In different regions of Japan (not to mention other „lacquer countries”) there are different nomenclature systems for urushi types. What is called Kojiro in Tokio will be known as suki sugurome in Tsugaru or Echizen and aka-roiro in most other regions. Same applies to almost all other types of urushi. Another issue are processes used which can differ, and names used to define quality of lacquer. Some words like “kuro” or “tōru” can be universal (black and transparent respectively). But others can be very different in different regions, and misleading (same name for different urushi, or different name for the same urushi type).
Types of urushi
The most common division of urushi types you will find in shops and websites is raw, transparent and black. This rough division is based on processing. Raw urushi (ki-urushi) is not processed in any significant way, but filtered to get rid of any solid pant parts, fiber, insects etc. Sometimes it is adjusted for water content. Transparent urushi (suki-urushi) is processed with nayashi and kurome processes. Black urushi (roiro-urushi) is processed the same way as transparent but with an additional step of adding iron sulfide which makes it black (but still a little transparent).
Another factor which differentiates urushi types is the addition of vegetable oil, usually perilla (sometimes tung, linseed or other drying oil). Addition of oil changes some characteristics of urushi – curing time, gloss, strength. Oiled urushi usually tends to cure slower, and is more glossy than un-oiled urushi of same type (without any polishing). It is used (not exclusively) for nuritate – final layer which is not sanded and polished.
Each of the above groups can be divided further into many types and quality levels. And the naming of those urushi types become even more complicated and sometimes misleading on this level.
One more important factor is the origin of arami-urushi (raw, unfiltered, unprocessed sap from urushi tree).. While it is mostly processed in Japan, the vast majority (98% !!!) of urushi originates in China and other countries and is imported to Japan. Pure Japanese origin urushi is usually much more expensive (3 to 5 times more) , and some types can be even more expensive – based on specific region, method of harvesting and even time of year it was harvested.
Rule of thumb is that urushi of Chinese origin is considered lower quality than Japanese and is cheaper. But this might be misleading as there are some special grades of urushi harvested in China that can as good as not better than some Japanese ones, but is still cheaper. This strong differentiation of price and “image” of Chinese vs Japanese urushi comes from history (years ago raw urushi imported from China was indeed low quality, usually a mix of different kinds, sources, sometimes with unwanted additions to pump up volume. But is not true anymore. Chinese urushi market and export matured and you can order 11 different grades of arami-urushi, including highes quality easily outperforming most Japanese lacquers.
Price of Japanese urushi is also driven up by limited supply and by the fact of legal requirements – some conservatory work on historical objects and buildings in Japan can be performed with Japanese origin urushi only.
Raw urushi
Raw urushi is generally the sap of urushi tree (arami-urushi) filtered. Traditional filtering is done by mixing arami-urushi with cotton, and then separating it with centrifuge, and filtering again through textile filters. Urushi is warmed in this process slightly to make this filtering easier (temperature lowers viscosity), traditionally in a water bath.
Raw urushi can differ in quality a lot, and can have various applications. Cheapest types, harvested from branches of trees (seshime-urushi), are used for ground work, making sabi and other mixes and puttys. On the other hand, high quality Japanese urushi from trunks of trees (kijomi urushi, isehaya-urushi) is used for polishing, increasing gloss, hardness of surface etc.
Raw urushi can be matured. It is kept in sealed, glass containers sometimes for many years to let the sap separate into fractions which differ a lot in composition. Impurities fall down on the bottom, some of them go up and float on the surface. The rest separates into 2 or 3 sections – one containing mostly urushiol and practically no water. It can be further purified and traces of enzymes left in it can be inactivated. Pure urushiol can be used as additive to other types of urushi to strengthen the film, to slow the curing process or to adjust viscosity.
Middle layer is further processed normally as low quality raw urushi, usually for nakanuri types of lacquer. Bottom layer contains little urushiol and a lot water and impurities, cures very fast, but does not for strong lacquer film on its own, so used to make puttys, base mixtures, glues – all applications where water and fillers (like tonoko or fibers) are added anyway.
In most shops you can find 3 basic types of raw urushi – basic lacquer for base work, higher quality lacger for fuki urushi and highest quality one for uwazuri. But in some of them it can up to 15 types of raw lacquer plus the option to order special “bespoke” types. Appart from obvious Japanese/Chinese lacquers they differ in 4 criteria – gloss, curing speed, strength and viscosity.
NOTE FOR BEGINNERS
You need just two types of raw lacquer, don’t bother to learn all differences and applications of others. Basic raw lacquer (usually called ki-urushi or seshime) and high quality wiping lacquer usually called kijomi, isehaya or uwazuri lacquer). Once you get to know them and develop you skills – look for other types more united to your needs.
Transparent urushi
Transparency in “transparent urushi” is not an obvious thing. In most cases it is translucent, it always has colour (from greyish brown, through honey to almost red), it is transparent only in very thin layers. This transparency depends on many things: quality of arami-urushi used for it, processing, age of lacquer, additives, curing, and of course layer thickness. Rule of thumb – the higher the quality, the more transparent it can be properly used. The thinner the layer – the more transparent. Slow curing benefits transparency, but only to some point (too slow and it becomes cloudy).
Similar to raw urushi, there are a lot of different types of it. The difference is – it is much more complicated. Right now I have 15 different transparent urushi in use, and this just a small part of possible options.
So what is the difference between them?
As with raw urushi – country of origin. Japanese and Chinese urushi are always listed by all urushi vendors and processors.
Then – basic quality difference – nakanuri urushi – for middle layers, and top layer urushi. This can be granulated further.
Then colour – you can find separately listed urushi with more red hue and with more grey/yellow.
Then other additives – most typical is vegetable oil as i mentioned earlier, added to enhance gloss to urushi used for nuritate lacquering. But also dyes like gamboge are added to nashiji urushi which is even more transparent, yellow and typically very high quality.
But this does not end here. Differences in curing speed, viscosity, special processing techniques promoting emulsification of urushiol, increasing gloss in without adding oil, protein added to lower the allergic reaction and increase viscosity, lower or higher water content etc. One of my suppliers lists over 20 types of transparent urushi and this is not including the bespoke processed offer.
Most common types and names you will find are:
- Kijiro urushi – most common, amber, semi-glossy or matte, used for kijiro technique on wood, and for roiro polishing.
- Shuai urushi – usually with added oil, glossy urushi for nuritate layer. Sometimes keshi-shuai – generally very similar to kijiro
- Nashiji – mentioned above, very high quality, with best transparency, yellow colour and typically with added vegetable oil (version without oil is often called togidashi-nashiji – suitable for sharpening/sanding). It is used for maki-e, for nashiji technique (“pear skin”, used to embed gold or silver powder flakes also called nashiji)
- Hakushita – used under gold leaf
NOTE FOR BEGINNERS
Choosing the right lacquer seems super difficult, so to make it easier, limit it to just a few types, most versatile. Buy kijiro, black or transparent nakanuri, and black top coat lacquer. This will be more than enough to try and learn many techniques.
Black urushi
Black urushi is processed in generally the same way as transparent urushi (and it is still often transparent) with one key different step – adding iron compounds, usually iron sulphide, which makes urushi black. Or to be precise – almost black in most cases, and often with brown hue.
Types of black urushi are in part very similar to transparent: middle and top layer, oil or no oil, one used under foil, etc. Obviously there is no nashiji. The choice is smaller but also the variety of uses – you can’t use black urushi for mixing pigments etc. Black urushi is used both for middle layers as well as for top layer. Highest quality black urushi is used for top layer in roiro-shiage technique, and after carefull sanding and polishig (dozuri) and then additive polishing (interlaced proceses of
Another category of black urushi, much less popular in ready made form is urushi made same way as colour urushi – by adding pigment. Most craftsmen prepare it themselfs, traditionally with pine soot, or lamp soot (carbon black, lamp black are typical names of those pigments), as it’s carbon particles are small. But with modern technology much superior pigments were developed. Problem with any traditional pigment is it contains a lot of other ingredients not beneficial to final product. Soots contain ash and oils, and even best quality ones can have 5 to 10% of those. Laboratory grade carbon pigment can be 99,999% pure, it’s particles an order of magnitude smaller, and much uniform. It mixes much better with lacquer and is more stable.
Colour urushi
Colour urushi is made by mixing pigments with urushi. But not just any pigments – urushi is acidic and contains oxidants (the enzyme which causes urushiol to polymerise and “cure” is basically an oxidant) so many pigments will react with it. Traditionally only a few colours of natural pigments were found and used with urushi, among which the vermilion colour stands out – made with cinnabar – mercurium sulphide. Process of mixing pigments with urushi is difficult and laborious. Or requires special tools such as roll mills. Pigment to urushi ratio is usually between 1:1 to 1:2 by weight. Seems like a lot of pigment, but this is the only way to let the pigment dominate the natural colour of lacquer. But for some techniques even more crazy ratios are used, like 1 part lacquer to 10 or more parts of pigments – to create a kind of putty for use in some decorating techniques. Creating a homogenous mixture the traditional way usually takes two separate processes and some time between them. First you weight urushi and pigment, and mix part of urushi with all pigment in a mortar. Once it looks homogenous, you protect it from air (covering with special paper or saran foil) and set aside. A day (or more) later, you start adding the rest of the urushi, working it in a mortar or on a glass plate with a tool with a flat surface until you incorporate the whole lacquer into the mixture. Once homogenous – it is done. But still needs to be filtered before use. Why to separate processes – to let the urushi penetrate the pigment, infuse it before another session of mixing. Exactly the same technique is used to make traditional oil paints, but due to lower viscosity – oil paints are much easier.
Modern chemistry brought many new pigments into the game. Starting with white (titanium oxide), through many bright versions of traditional blue and green, to crazy pinks and purples and even metallic urushi, made with metallic pigments, usually aluminium coloured with very stable resins.
Another interesting but much lesser know group are transparent colour lacquers. They are made with oil soluble dyes instead of pigments, are much rarer and more difficult to make stable and at least somehow transparent.
NOTE FOR BEGINNERS
Do not mix your own colour urushi. At least do not start with it. Why? To do it well you need to prepare at least 100g at one go – it’s a lot of urushi. You need tools (mortars, mixing plate etc). You need to know how to store urushi. And you need to buy special pigments anyway. Of course – it is a lot of fun, and you can learn and gain experience, but do not start with it 😉 It will go wrong almost for sure. You can easily buy premixed colours: white, 2-4 types of red, bright blue and dark blue, green, yellow and purple at almost any vendor. Some vendors offer up to 100 colours, and offer a colour matching service. But you can mix basic, easy to buy colours to get even more shades. Just remember to slowly add small amounts of darker colour to brighter one. And have fun 😉
RED URUSHI SIDENOTE:
I often get questions from urushi enthusiasts who start working with colour – why my red is different than yours. Or – how to get the same red as Namiki 50? Mine is different. The problem is – there are a lot of reds. I counted over 30 red pigments on the market. One pigment maker can offer up to 8 different shades of red. Ki-kuchi neriu-shu, ho-shu neri-shu, aka-kuchi neriu-shu etc. Moreover – the type of urushi used to mix these pigments wil influence the colour a lot. Curing will influence it too, sometimes the most (rendering orange bright urushi dark brown). Patience – learn to cure, learn how colour behaves, how it changes duriung curing or depending on urushi:pigment ratio. TEST every new irish you buy first on a test board with different humidity and temperature settings.
