The way I got the dark background was accidental.
I was trying to finish the inside and I poured in the wipe-on varnish and rolled
the piece around. About the time the vase was coated inside, the liquid was
gone. It was absorbed into the wood.
I did this about three times before I figured out what was going on. I then used
white glue inside, brushing all the surfaces, then used a wet paper towel to
wipe up and smooth out the excess. This was to seal the inside so the varnish
would no longer soak in.
Then I gave the inside a number of coats of varnish, plus more coats on the
The effect though, is that the thin wood went dark from the varnish soaking into
the wood, and the thick areas stayed light as the wood did not get as much
I don't know how it would work if I planned for that, but it had an effect
BTW, I had dripped some vegetable oil on the inside a few weeks ago and it bled
through. About a week later, the oil had dissipated, absorbed by the surrounding
wood so there was no sign of it.