Here's a quick tutorial on how I create the 'feather' effect in my spoons.
Split the wood tangentially. The billet must be oriented as shown in the diagram.
It is important when creating the billet that the growth rings at the handle end are even either side of the centre line, otherwise the feather effect with be uneven.
Wood with more/tighter growth rings will produce more feather lines.
The more extreme the crank, the more rings you carve through, which means more feather lines. But don't make it too steep or the spoon will be less strong. You need to compromise!
Carve two flat bevels either side of the centre line to create a ridge down the middle of the handle.
As you do this, you'll see the feather effect appear.
Carving wood in this orientation with produce these circles in the bowl, as well as the feather effect
*Please note: This works best when using wood with a strong grain that will enhance the lines.
You can also use ring-porous wood and rub ground coffee, cinnamon or another powder to highlight the grain.