You are correct. Cashew lacquer is similar to, but not the same as, urushi lacquer.
So there's urushi lacquer, cashew lacquer and shellac... which is the best? Shellac?
I simply use shellac on most of my stones. For $10 at Lowes, it can't be beaten. However, my best stones are done the "traditional" way, in Urushi. But as Stefan mentioned, and I can attest to the fact, it "can" cause severe allergic reactions. Also, if you are in the US it is quite difficult and expensive to get Urushi, but if you ever get to visit China, Korea, or Japan, it is much easier to come by.
At Death's Door You Only Have 2 choices. Die Happy or Die Regretfully.
Knowing this...........Choose 1 and Live!!!!!!!!!
I use clear lacquer. As much as I wanted to do it the traditional way, the cost of getting urushi here was just way too high.
I am all excited now...Might have to get with you Maxim, and get me some Jnats