Well it seems like there's controversy regarding the ability of solvents to cause tung or linseed oils to penetrate deeper into wood. My two cents, which are worth a penny these days, is that the particles that make up tung or linseed oils are larger than those that constitute solvents - I may be wrong. But if so, the oil is only going to go down so deep into the wood - based on its density - and the solvent will go deeper - based on lesser density. Its kind of like how things migrate through soil (or how soil is formed) if you ever look at the sidewall profile of a trench. To me, solvents have always been a way to thin the materiel I use for the finish. So if the tung oil I am using is too thick and gooey I can make it work better by thinning it out with a solvent (being the son of a mechanic I have to say that solvents were usually good for cleaning up parts and jobs and not much else). I think artist use this idea when adding linseed oil to paint to make it flow better or to increase its working time before drying. Anyhow, that's my two cents worth which I'm sure has suffered considerably from the effects of inflation in the short time it took to write this post. Thanks again to everyone who kicked in on this post. I appreciate your help.
A very important point you made is about increasing working time of your finish... that is absolutely true. But because the solvent evaporates leaving less finish it is often confused with speeding the drying...
There is no magic; it cannot increase working time (pot life, open time, etc) without delaying curing.
