Chris Poplar is a soft wood with lots of room within the fibers of that wood, it can contain lots of water or lots of oil.
I don’t know why you would use raw linseed oil though, it wont harden up for eternity, I made that mistake to use it on a picnic table I build some 50 years ago :o, it turned all black and stunk, as the oil got rancid and fungus got into it, as I was told it was a good oil for outside use :mad:.
I have turned a few pieces of Poplar, but I turned them mostly thin walled and then used PTO (Polymerized Tung Oil), not to get a shiny finish though, just a more low gloss that I like on something like that.
I will always just get enough oil to cover the wood, let stand for about 10 minutes en than wipe the bowl dry, set the bowl in a warm dry place and let the oil harden, takes a good night or usually a day for me before adding another coat, and repeat this as the first one, depending the gloss you want, you might need just two or maybe 4 or 5 for high gloss.
If you want to polish it, wait at least a week and better longer than that to get a harder finish that will give you also a higher gloss.
When spalted Poplar can look good, plain it is a rather boring wood, turned very thin it will show the light through it.
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This one has a thicker wall as the wood was already too soft for a clean cut, even a skew was barely able to make the outside smooth, and the inside was harder to do of course no skew but a spindle gouge was giving me the best cut, and still had a bit of roughness in the bottom.
Mind you I would NOT recommend using a skew or spindle gouge on a bowl ever, this is the do as I say, not as I do.
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