Thanks Wolfgang for the explanation. \setupblank[fixed,big] works very well too. Now for another question. I have modified "SlideWithSteps" from
http://wiki.contextgarden.net/SlideWithSteps
It seemed not to like \eject and I replaced \phantom{ ... } with \setlayer[StepsHiddenLayer]{ ... } where StepsHiddenLayer is a layer created with
\definelayer[StepsHiddenLayer][state=stop]
See attached slide-with-steps.tex
This seems to work fine with itemized lists and even MetaPost figures (see foo.tex) but it fails with multiline equations (bar.tex) which are both attached. I would like a solution that would allow me to reveal each line of a multiline equation.
Troy