Now as I mixed in the DME supplied with the kit (its an all dried ingredients kit) the wort foamed up a bit, as expected and as I'd previously experienced in other kits.
However, when I added the Brewmaker DME the wort no longer foamed up. What few bubbles there were lasted a minute at best.
Has anyone else experienced this? Why the sudden change?
I suppose that its unlikely that my final pint will hold its head either as a result of this? Not too much of a problem being a southerner
but it would be nice to have some head on it 
Moral of story: I'd stick with Muntons Spraymalt if I were you
