Poses were as follows: five thirty second poses, five one minute poses, five two minute poses, a few five minute poses, several ten minute poses and one, final, fifteen minute pose.
We discussed the play of light on form in terms of highlight, halftone, shadow, shadow core, reflected light and cast shadow using an orange and an egg.
At the end of class Carlos showed us his painting of pomegranates which illustrates the example of light on form. 
Leonardo used an egg to think about highlight, halftone, shadow, reflected light and cast shadow. Soft-edged form shadows and hard-edged cast shadows could be added to the discussion.
Carlos's painting of a Hudson Valley landscape which is an example of the play of light on a really big sphere, the earth.
Set an egg on a desktop, light it in various ways and draw it a few times, capturing highlight, halftone, shadow, reflected light and cast shadow. Next time you draw a head see if the egg study has any bearing on portrait drawing. Remember to squint.
