We have a good discussion going on so let's keep it going...
Ditto. I spoke my mind but there's nothing wrong with venturing off topic and I shouldn't have been so feisty about the guitar strings, etc.
I've tried this "pure" tung oil and the citrus solvent (limonene from oranges). My organic chemistry (Ph.D) tells me that pure tung oil dries/cures by exposure to oxygen without any added "drier catalyst" to give it a boost. Take a look at the before/after pics in the "Wood Samples" section and read the "Directions for Use" section. It's worked fine for me and I've had no drying problems with it but some claim that tung oil "takes forever to dry".
https://www.realmilkpaint.com/shop/oils/pure-tung-chinawood/
BTW, Waterlox Original Sealer/Finish is about 25% tung oil and 75% mineral spirits. It contains 0.1% cobalt naptheneate to catalyze the drying process with oxygen.
Dan, what brand name/variety are you using? I can probably find that drying additive.