...quality of tools and materials and expertise in their application comprise a substantial part of a tradesman's work and have a major effect on its quality. Not so the painter....
Uh...not so much, Frag, sorry.

Allow me to elaborate a little on this.
To make a painting you first need a piece of canvas stretched over a canvas stretcher, sized and primed. The canvas stretcher must be made of good solid wood, each piece straight and free of major flaws that may take up or lose volatiles as time goes on and make the stretcher frame warp. The stretcher frame must be assembled solidly and braced so as to resist the pull of the canvas when it is stretched.
The canvas itself should either be linen or cotton canvas that has been treated with something along the lines of formaldehyde to prevent the cotton from rotting. (MOMA had a painting that they paid a huge chunk of change for some years ago that was done on raw cotton canvas. It literally dry rotted off the wall of the museum and was a total loss because the 'artist' had failed to properly prepare and prime it.)
Whether you choose to use linen or formaldehyde treated cotton canvas, the fabric
must be sized and clean. One side of the canvas is tacked down securely to a side of the stretcher. The canvas is then stretched from the opposite side of the stretcher with a pair of "canvas stretching pliers" and tacked down. A remaining side is then lightly hand stretched and tacked down. The last side is then stretched with the canvas stretching pliers until the canvas just begins to tear. You do this in a quiet room and pay close attention as you pull the fabric to know exactly when to tack that last side down.
The stretched canvas is then primed. These days we use a water based acrylic gesso rather than applying a white lead paste with a palette knife. It is at this point that the need for a proper stretch becomes obvious to the initiate. The pores of the fabric
must be open enough for the primer paint to penetrate such that it beads up on the back side of the canvas resulting in a batch of little round primer paint beads that can easily be felt if one runs their hand across the back of the canvas.
This forms a
physical bond between the primer paint and the canvas fabric in addition to the
chemical glue bond that the rabbit skin glue or acrylic polymer adhesive makes with the fabric.
Why is this important? Because canvas picks up water from the air very rapidly and contracts as it does so, making the canvas a little bit tighter than it was. As the canvas then loses the water back into the air it relaxes and loosens. We refer to this as the canvas 'breathing". As the years go by, this breathing loosens the glue bond between the primer and the fabric. If the primer has not bled through the canvas and formed the beads on the canvas back the primer paint then begins to let go of the fabric and pieces of the painting begin to fall off. That mechanical bond is of critical importance to the longevity of the painting. At this point there is no way to stop the chipping and flaking other than to maintain the painting in an absolutely stable thermal and hydrologic environment, like in a hermetically sealed showcase or to remount the canvas on a rigid surface like masonite.
A professional artistic painter
should know and employ this technique (though many do not), a hobbyist or naive (uneducated) painter will not. If one is looking for a work of art as an investment as well as a thing of beauty than it behooves one to use a professional and to examine not just his/her work but the professional credentials as well,
just like with any other profession or skilled trade.
I appreciate that anyone can buy a pre-stretched canvas from the art supply store and just paint on that. That canvas was primed loose on an assembly line and then stapled on the stretcher. It
was not ever "stretched" so the primer will eventually fail. That is OK for students and hobbyists, but NOT for professional grade art.
It is the difference between an "artist" and an "artiste" as well. As you may well guess, I would be absolutely thrilled to go on about this in greater detail.
