Michelangelo would refer to his model collection
to see if there was anything he could use from it.
to fit the commission.
Since he had a photographic memory this step was automatic.
A Bozzetto , or sketch would then be made on paper, clay or wax.
A full terrocatta or wax model may be made or even a
bas-relief made for the painting..
Or a detailed sketche would be made for the painting.
This is called a presentation model ir sketch and would
presented to the patron for approval.
A large drawing or cartoon would be made if the painting was large.
The outlines of the drawing in the cartoon would be
tacked to the painting surface. The
cartoon would then be tapped with a porous bag of charcoal
The charcoal dots would then be painted
as one line
On large paintins where the surface was distored like the
ceiling of the Sistine Chapel, IMHO, Michelangelo would redo the
outlines with a brush attached to a long stick.
evidence of corrected lines when the ceiling was last cleaned.
Or, he could have used a
shadow cast by a model. However, the corrected
lines found on the ceiling shows he redew all the lines pounced not
just the outline of the figure which a shawdow would cast.
Michelangelo would then paint the picture.