I have several DaVinci colors on my pallet. After I squeezed them out of the tube, they never "settled in", but stayed in little piles in the corner. When they dry, they pop out of the wells and rattle around when I move the pallet. When I spritz them, they take a long time to "melt".
On the other hand, I have two Van Gogh colors on the same pallet that settled in nicely, stay where I put them, and moisten up very nicely when I spritz them.
So, I solicited some advice on an artists forum, and the answer came back with half of the replies recommending a drop of gum arabic, and the other half recommending a drop of glycerin. I chose the glycerin.
That may not have been my best choice.... 48 hours later, the paints are still liquid and gooey in the pallet wells. I'm worried that they may never actually dry again.... because that would be messy. I'm not terribly worried about cost. I got these tubes on clearance, and I don't like them nearly as much as Daniel Smith pigments.