From http://www.hakuminurushi.com/
Raw usushi needs to be cured, after this process pigments are added to the cured urushi in order to create colored urushi. Black, red and rust brown are the colors you are most likely to find along with treated bare metal (tetsu sabiji).Urushi is to many, a miraculous substance. It is the sap from the lacquer tree, Toxicodendron vernicifluum, a plant closely related to poison ivy, and as such, considerably toxic. As with its better known cousins, the poison ivies, oaks and sumacs, contact with the tree can cause an unbearable affliction of rashes and blisters. Yet somehow, in some ancient time, someone realized that this liquid—the life-blood of this wondrous tree—holds a hidden potential.
Urushi, as it has come to be known by its Japanese name, naturally cures through a process of oxidation and polymerization into a material with remarkable properties for a natural substance. Once hardened, urushi forms a tough and scratch resistant surface impervious to water, alcohol, minor heat, acids and bases. Because of these properties, as well as its characteristics in application, urushi has an incredible versatility in use from architectural elements and utilitarian wares to fine arts and crafts renown for their beauty and intricacy.
With proper care and skill, urushi creates a wonderful luster that, when combined with countless different decorative techniques, can create objects that are as functional as they are beautiful. Metal powders, nacre, and eggshells, or even substances such as albumen, tofu and flour can all be used in conjunction with urushi to create exquisite patterns and designs derived sometimes from the skill of intellect and craft and sometimes from the whim of chance and serendipity.
Regardless of the technique, the end results capable of urushi are nothing short of miraculous. Yet in this modern time and age, where meticulous crafts of the hand are being threatened by industrialized mass production, the use of urushi has slowly been at a decline. When once Japanware was considered at the pinnacle of the functional arts, it is now little known outside of Asia and specialized circles.
Nevertheless, the craft of using urushi has not yet died out, and there are still many discoveries to be made as craftsmen continue test new techniques and combine modern materials with ancient knowledge. And so, hopefully, the beauty of this wonderful craft will be passed on through many more generations to come.
COMMON TERMS from http://www.hakuminurushi.com/urushi/glossary.html and other sources.
Urushi=lacquer
Nuri=Painting, layering, coating. A term used to denote a lacquer object or technique as opposed to the lacquer itself.
Arami urushi=The unprocessed sap taken straight from the lacquer tree. At this point it is a milky white liquid that cannot be used as lacquer without further processing. The sap is filtered and left to sit for an extended period of time to allow partial oxidation as well as evaporation of some of the water content. Once the liquid reaches the proper water content and oxidization levels, it can be used as lacquer and is then called ki-urushi.
Ki urushi=Raw lacquer(also nama urushi). Raw urushi after it has been filtered and slightly reduced in water content to make it usable as lacquer. There are different types of ki urushi depending on the origins of the tree as well as the season that the tree was tapped. Hatsugama (also hatsu urushi), collected early summer, has a high water content in the emulsion and has a high adhesive potential. It is used for adhesive mixtures and for suri-urushi. Sakari urushi, collected late summer, is used for processing into
kuro urushi and suki urushi. Oso urushi is collected early fall and urame and tome urushi is collected at the end of the season in late fall prior to cutting down the tree. Eda and seshime were traditionally collected from the branches during the winter after the tree was cut down, but in modern times, low quality urushi from China or a mixture of Japanese and Chinese urushi is sold as seshime.
Kuro=Black
Kuro urushi=Black lacquer.
Shu=Red/vermillion
Shu urushi=Red lacquer.
Sabi urushi=A paste made by mixing powdered burnt clay "tonoko" with seshime-urushi (sap taken from the branch of the lacquer tree). Fine wheat flour is often added. Sabi-urushi was used as a preliminary lacquer layer "kataji" on wooden statues, and often found on late Heian and Kamakura periods bugaku masks "bugakumen". It was also used to build up surfaces in raised lacquerwork takamakie.
Sabiji urushi=Brown colored lacquer that imitates rusty/russet iron.
Kin=Gold
Kin paku=Very thin gold leaf that covers a lacquered surface.
Gin=Silver
Gin paku=Very thin silver leaf that covers a lacquered surface
Tetsu=Iron
Tetsu sabiji=Russet iron, a complicated process that allows bare metal to be exposed to the elements without being destroyed.
Byakudan urushi. A rare lacquer made by covering a gold or silver lacquered surface with a transparent layer of red lacquer which lets the underneath precious metal shine through.
Tetsu seishime urushi=Russet iron surface treated with a special process involving the application of raw urushi which once dried is heated for a few minutes over a charcoal brazier. The resulting deep, matt brown finish is also resistant to rust.
Kokuso / kokuso urushi=A mixture of wood powder, sawdust, or plant fibers with nori urushi or mugi urushi for use as a filler or putty in both the substrate before lacquering and in repair of damaged pieces.
Tataki urushi=A lacquer finish that features a raised relief rippled texture.
VISUAL EXAMPLES.
Sabiji urushi.
Shu urushi.
Tetsu sabiji.
Kinpaku urushi.
Kuro urushi.
Tetsu seishime urushi.
Gin paku urushi.
Byakudan urushi. This European helmet was modified for use in Japan, the inside is an example of Byakudan urushi nuri.
Tataki urushi.
kokuso urushi. Used as a filler as in this example of what looks like a suji bachi kabuto but is actually built up using kokuso urushi and other elements.
The results are worth a little discomfort however. 
