I had been reading some more about underpaintings and their functions, so I decided to give it a go for the still life I was painting.
In the end, it didn't have much effect on the final work (i.e there aren't many parts where you can see the underpaint shine through) but I think it did help me with choosing colors and values. In any case, the painting turned out pretty well, I think... quite accurate to the photo I was referencing and I was particularly pleased with the glass/water (apart from the wonky, non-circular shape which is a big no-no!).
