Q: Can you use tongue oil on wood and then cover it with a polyurethane?
A: Yes, absolutely. I don’t think I would recommend pure tung oil given how long it would take to dry and it’s cost. There is a tung oil based product called Waterlox that would do the trick nicely. www.waterlox.com. Guys who use this product in the U.S. like to give 2 coats of Waterlox and 2 coats of their finish of choice. Personally, I like to go straight Waterlox. You can’t beat it’s ease of care.