Jane Minter's blog where she has done this exercise to check the transparency and staining properties of her palette and it reminded me of this I did last Summer. It is such a useful thing to do and I got one or two surprises as well!! Some colours I thought were transparent, were semi-transparent eg the Schminke May Green, am sure if I'd checked on the tube I as I was buying it I would have found the answer!!!
My raw sienna is also semi but I must admit I historically I have a few makes of it and not sure if it was W&N I used, which is meant to be transparent.
I have added a few colours to my palette since I did this and now I tend to stick to the transparent colours, most of which tend to be staining as well so although not as easy to lift off these for me are the jewels of the colour world, whether the staining quality adds a richness I don't know but they are the colours I am drawn to!!!
I know many of you will think this is too much trouble and you can't be bothered, but I would advise everyone to have a go at this, there is nothing like seeing it for yourself and also checking out your own paints. The principles seem to stick better when you actually see it, it helps you understand and more importantly remember when you have actually done it and also provides you with an instant point of referral for your own palette.