Is there a lower recommended max level when boiling?

[squadricus]

I was trying to make a 2L wort starter (dry malt extract and water) for yeast for brewing in a TM21, got a little spooked at being able to boil that in the thermie without boiling over.  I chickened out and poured it out into my Kenwood (3 L cooking capacity in 8 L bowl).

Any advice out there for how full a pitcher can safely be boiled with something prone to foaming up?

[Cornish Cream]

Because you are at the maximum level in the TM21 I personally would brew in another pot. Very wise of you to put the starter in the Kenwood.

[cookie1]

Especially if it is prone to frothing up.