How
to
Prime and
Stretch a Canvas
A Newcastle Arts Centre Guide
Canvas is the traditional
painting surface for portable paintings.
However it is not
dimensionally stable, it can shrink or stretch with the
wetting or drying of the primer, paint or atmospheric
changes. It is important that the Stretcher bars are made
of well seasoned timber and the canvas is strong. Linen
canvas has always been chosen for professional work
because it is strong and resistant to rot. Cotton is
cheap, less stable and prone to mildew. Canvas must be
‘sized’ to control the absorption of liquid by
the fabric.
Careful priming of your
canvas is important and this should be done before your
canvas is stretched
although it is possible to size & prime a lightly
stretched canvas. Priming a canvas requires a lot more
care than a wall or board because canvas is flexible and
will crack a brittle primer. It is therefore essential
that the primer remains flexible. Traditionally rabbit
skin glue was used as the size because it retained some
flexibility; today a good quality PVA such as Marvin
Medium does the job well and is a lot easier to apply.
There is a myth that
Acrylic paint can be applied to a raw canvas but this is
unwise as the medium isabsorbed by the canvas to leave
the paint with a chalky surface that is prone to damage
and almostimpossible to clean or restore. After sizing,
two thin coats of Acrylic Gesso Primer will create a good
surface for Oil or Acrylics paints. Acrylic primed canvas
can be improved for oil painting by the application of a
thin coat of Thixotrophic Oil Primer. A good test for a
canvas is to dab a spot of white spirit on the front of
the canvas then check to see if it soaks through to the
back, if it does, the priming requires more
work.
To stretch your canvas,
first assemble the stretcher bars on a flat table or
floor.
Make sure that the frame is perfectly square; check this
by measuring diagonally, corner to corner.
You will need a staple gun and a
pair of canvas pliers.
