calcium caseinate
Within a few minutes should be fine...Last night when I had it for the first time I put it in water on it's own first to taste it without adding chocolate WPI...It's drinkable on it's own, flavorless for the most part. I threw a scoop of WPI in after that and drank it straight away.
This morning I mixed it up and put it in the fridge for maybe 15minutes before leaving for work...When I started drinking it I tasted a hard piece and thought it just didn't mix, so I shook it, and noticed white hard pieces settle on the bottom... So yeah, drink it straight after you add the water and it should be fine