The difference between slip & underglaze

What is slip?

John Britt: Great tutorial about understanding slip versus underglaze

Recipe:
70% clay bonedry 254 draaiklei wit
5% bentonite (my own change)
15% kaolin
10% potas feldspar

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What will we expect?
-Shrinkage of the slip might be a problem as the Nigra clay has much less shrinkage than the white slip.
-Also I added 5% bentonite.. this may be a little too much. Advantage is that the slip is beautifully brushable.
-As an experiment I took 200 ml of white slip and added 6 grams of copper carbonate. I am hoping for a beautiful green slip.
-Furthermore I am curious if the transparant glaze will run more when used over the copper slip.
I am hoping that 2 coats of MF3 will give a high gloss finish over the nigra clay.