Tung nuts are not all the same. The more picky companies will buy only nuts that are generally of a good quality and will yield more oil per weight of nuts. Many rural-based companies buy everything they can get their hands on.
Some nuts do have lower oil yield, but that does not necessarily mean the quality of oil is any worse, only that the profit margin is more narrow. The benefit of working with the higher grade companies is that they are a bit more organized and can give much better details about the grade of oil being sold.
The pencil in this photo is only to reveal the relative size of the tung nuts. The tung nuts on the left are higher quality nuts and the type that the bigger companies try to buy. The nuts on the right are not as nice and will yield less oil per weight.
I will have to admit, my statistics for these two sets of nuts have been sitting unused for so long, I am not so sure on the nicer nuts, but I can confidently relate the figures for the right side nuts. They had an over all proportion of 22-26% oil (in Chinese that is simply called "liquid percentage"). That is 22 to 26 percent of the nut is oil.
Those are the bad ones. Finding these figures takes a microwave and a few measuring instruments, but just with a quick look at some tung nuts, some distinction can be made as well. The nicer nuts have a lighter color, more of a brown shade. The nuts on the right have a lightly powder-like feel, are darker, and often have a deep red color instead of the brown.
The Liuzhou Guangxi area has all kinds. In fact, some of China's finest tung oil comes out of the Guangxi and Guizhou areas. They are ready to export, but right now sell mainly through tung oil co-ops.
