A chemist sent me an email pondering whether tung oil cloudiness is in the oil, or if it’s a matter of texture, or surface geography. I was curious, too, as I have had one anomalous test piece on wood cure with glossiness using raw tung oil and japan drier, but I’ve never seen the same thing since.
To get pictures, I bought two glass plates at the dollar store and put a coat of tung on them, and linseed on another, and a 50/50 mix of washed Swedish linseed oil on a third spot. The linseed oil dried clear and was unspectacular, and the 50/50 mix was close, so i have no pictures of them. The light passes right through and there’s not much to see.
It turns out the frosting is typographical. If you build tung on a surface, you can wet sand it to a gloss, and/or top coat it with something that levels and it will be functionally clear.
You might find the tung oil pictures interesting in the same way a close up picture of an insect eye is interesting.
Below is a group of three pictures at different magnification, but the same spot.
You should be able to click on them to get much larger versions.
As the finish gets thinner, the topography is lower. The density of tung when cured changes more from raw oil than does linseed. It’s a curious question as to whether it expands some first before curing, as the top layer increases in surface area without the finish pulling away from edges, so it’s not similar to the effect of wrinkling paper. Changing circumstances of drying temp and thickness layers affects how coarse the frost topography is.
Various other pictures follow. But before them, one side piece of knowledge here. I wanted to water test all three oils or mixes. Turns out, even the linseed oil will allow standing water on it to dry over an extended period, and any mineral scale can be wiped off without affecting the oil film at all. I’m not going to test cheap hardware store oils to see if they degloss, but it was a surprise to see how well linseed oil with 1% Japan drier does against water, contrary to the myth that it performs poorly against moisture.
Rosin and linseed varnish, on the other hand, is ruined quickly by any water that is allowed to lay on it, and is thus a good reason to use tung for rosin resined varnish instead of linseed.
Anyway, the pictures:
Of Making by Hand with Wood and Steel 