Mujitsu and Tairaku's Shakuhachi BBQ

Hi Perry,
So there is no artificial lacquer or varnish that can do the job other then urushi?

Having used cashew, it does eventually cure to a glass-like hardness. It reacts with moisture in the air in the same way that compounds in urushi do. It can however be a bit gummy/spongy if it hasn't been allowed to completely cure before being pressed into service. That tends to happen when folks think of it as paint and apply it too thickly, too quickly, or both. It is a common error. The thicker it goes on, the longer it will take to cure. If it is too thick, it may take months, hence the sponginess; a thick layer slows up the water vapour reaching the bottom of the layer. Some folks may exacerbate this by trying to use heat to dry out a thick layer, not realising that it is not paint and that it hardens by reacting with water vapour, not by solvent loss. Then it can get really spongy.

Thin layers are best, as well as not using it until it has properly hardened.

After cashew lacquer has cured properly, it shouldn't break down in a hurry. As I said, chemically it behaves like urushi. You can however get it to crack or chip by mishandling the finished product or problems with the underlying material, but that's true of urushi as well. I've seen urushi flake after a chip allowed water vapour between the lacquer and the wood. So part of using cashew lacquer properly is getting an excellent finish on the wood first, same as it is with urushi.

Oh, and you can thin cashew with a standard xylene based universal thinner.

However, there is now a problem with getting hold of cashew lacquer. According to our Japanese supplier, new shipping legislation means that it can't legally be exported from Japan by either air or sea. Our supplier is a bit fed up with this, but they have stopped exporting it. Since they appear to have been the ultimate source of all the cashew lacquer in the West, this is going to leave a lot of folk with a big headache. The company that makes it isn't going to ship it either. They're adamant on that.

There is one small ray of sunshine in this news. Not being the sort of folk who just give up, we've been trying to get the stuff made under licence in the UK. At present it is looking optimistic, but there are still hoops to jump through. Well, the alternative was not having access to the stuff at all. Keep your fingers crossed and we may be able to get the supply renewed.

Kevin

Last edited by Kevin Jones (2010-10-20 10:28:23)