How should fluid acrylic paintings be protected?

Some of my customers, gallery owners, and fellow artists have asked about my gallery wrapped acrylic paintings and how I protect them.  Often people think acrylic paintings don't need to be varnished since acrylic paint is in essence a very thin layer of plastic when dry.  Since I do my acrylic paintings on watercolor paper, I started to varnish my artwork to protect the paper from humidity in the environment.  

However as I researched varnishes to ensure I was using the right materials I learned that any acrylic painting should be varnished for a couple reasons.

• The pigment in the paint needs to be protected from ultraviolet (UV) light to reduce the chance of the color disappearing over time
• To protect the surface of painting from the elements and be resistant to dirt retention and discoloration

Aerial Bikes II, 13.5" X 22" gallery wrap

If you have read my blog post "Some basics things to know about watercolor" you know already about how important it is that the artist use high quality materials that are light fast.  In other words pigments that won't lose their color quickly.   

Even though I use the best materials I can find to create the painting, I also make sure that either the glazing I use has UV protection or, in the case of gallery wrapped art, the varnish has UV protection.  This practice increases the life expectancy of paint even longer. The need for UV protection is not unique for watercolor and acrylic paintings.  Oil painters have traditionally varnished their work for the same reason.

One of my larger gallery wrapped paintings, Freight Yard, 24" X 45"

I initially used only Liquitex Archival Permanent Varnish which I apply with a small 4" wide foam roller. I found that the smaller gallery wrapped paintings remained very flat when I varnished them. However, some of the larger paintings ended up with ripples in the corners of the art.  I experimented using different staples and staple guns when stretching the paper, but still sometimes ended up with ripples.  

I observed over time that when applying the first coat of varnish that I press fairly hard in the corners to get a solid coat of varnish.  This process appears to stretch the paper and I believe the paper does not shrink back to its original size because of the varnish.  As a result I started to use spray varnish for the first coat or two to avoid stretching.  I have used a variety of spray varnishes including Golden Archival Spray Varnish and Krylon UV Archival Varnish.

Spray varnish is a method to have a nice solid coat of varnish already on the entire surface of the paper before I use the roller to apply the later layers of varnish.  This approach seems to eliminate ripples from forming (most of the time).  Serendipity does sometimes prevail and I might get some ripples. Perhaps the level of humidity in the air is the culprit.  If you are an artist, don't give up; you can re-stretch the piece, as long as you are careful,  generally with good results.