Difference between Canvas print Spray and Varnish

[Amit]

I was talking to vendors regarding the difference between Spray and Varnish for Canvas Photo Prints. The reply which I got were not convincing and were following:

1. Spray coating is easier than varnishing
2. Spray coated Canvas print has less life than Varnish coated(roller) Canvas print

I was not convinced with these answers. Please help to get exact difference between the both and advantages of either of them.

[John Nollendorfs]

Amit:
You have to be very careful in choosing your canvas products, or your prints will come back to bite you in a few years.

First, make sure the canvas you choose, has a water resistant acrylic gesso coating. Many years ago, I was using a canvas product with water soluble gesso, and spraying that with Kamar type varnish sprays (since this is the type of protective spray that many artists use on their paintings). What has happened, is those canvas' have developed a craquelure. While this looks quaint if you want an "aged look", I don't think that's what you clients would appreciate.

Combine the water resistant canvas (matte in appearance before coating) with a vinyl acrylic top coat, that can be applied either with a roller, or an HVLP sprayer. The sprayer allows you to apply a thinner coat and thus give the canvas less of a "plastic" glossy appearance. Some of these top coatings need to be diluted with water, so check the coating's instructions carefully. These coatings initially have a slight milky appearance, but dry clear.

The HVLP sprayer can be bought quite inexpensively ($15) at stores like Harbor Freight. But you will need a decent size compressor to feed it's appetite for air (3.5-5 CFM). Also, you can purchase a nice $30 pneumatic stapler at the same store for stretching your canvas'.

[Amit]

Thank you for sharing the experience in detail.

As you said sprayer allows a thinner coat on the Canvas Print, so is it only the glossy look that differs in the Sprayed and Roller varnished Prints?

Does a thin coat or Thick coat even have any other impact in terms of protection longevity?

[John Nollendorfs]

I generally use 2-3 "thin" coats. A thicker coat could possibly help with abrasion resistance? But in terms of sealing the canvas for atmospheric oxidation resistance and for water spills, the thin coats should be more than adequate.