Below is from the Breathing Color site. Their coatings seem to work well for inkjet prints on canvas which is what Giclee prints are. Jim-p has the link in his answer to this question. I have dealt with them on paper and canvas and they are very helpful and will go out of their way to get information for you. They deal heavily in the high end digital market and not much with the small home and hobby printers. A good resource for information as well as a possible source for you to get canvas to re-sell to some of the giclee printers who want to try it as you become known as the 'go to shop' for their framing and information.
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Post-Print Protective Coatings
Canvas Varnish | Giclee Varnish
Giclee Coating for inkjet canvas
Giclee coatings, otherwise known as canvas varnish or post-print coatings, serve to protect, preserve and enhance fine art and photographic prints produced on digital inkjet printers.
Canvas varnish protects and preserves the giclee prints by inhibiting harmful Ultraviolet light from burning out optical brightener additives and other fluorescent whitening additives, which inhibits the inkjet canvas and/or fine art paper from "yellowing". Canvas varnish also protects against moisture and abrasion.
Canvas varnish enhances prints by increasing density, which brightens the color of printed images. For example, the "gloss" or "semi-gloss" finishes can make blacks darker, reds deeper, and yellows brighter. This intensity of this effect is determined by the intensity of the gloss in a coating, and nearly all giclee varnish coating manufacturers only offer one to three finishes that you are forced to use. If are not satisfied, then your search continues.
It is for this reason that we developed Glamour™ II Veneer (See the Media Coverage of this product), a canvas varnish and/or giclee varnish that is suited for both inkjet canvas and fine art papers. This proprietary giclee coating comes in gloss and matte finishes that can be mixed together to achieve every required "look and feel" known to man. Printmakers who use Glamour™ II Veneer have no limitations. It can be roll-applied, brush-applied, and sprayed. It can even be used as a very effective mounting adhesive.
To assist in the application process, we introduced an innovative roll-applicator system called The RollerFoam Kit (See the Media Coverage of this product). Rollerfoam Kit provides printmakers with a quality coating solution that is affordable (less than $10.00), easy to use (only one coat is necessary), and leaves no streaks. See our Instructional Application Video.