The Van dyke brown print is based on the
first iron-silver process, the argentotype,
invented in 1842 by the English astronomer,
Sir John Herschel. Both processes utilizes
the action of light on ferric salts and have
very similar chemistry. Van dyke brown is
considered a printing-out process in which
an enlarged negative or 3-dimensional object
is laid directly onto the sensitized substrate
and then exposed to light. The exposed
areas turn brown while the unexposed
areas wash away.This process is extremely
versatile - the sensitizer can be applied
to a variety of substrates including
handmade papers as well as fine fabrics
such as silk.