Varnishing paintings on burlap

I was wondering for quite a while already whether it's a good idea to varnish my paintings on burlap and how I would varnish them: matt, satin or glossy. The special appeal of those pieces comes from their rough, velvety surface, after all, and they look quite matt, especially those I did with my own oil paints. I just had to try varnishing them, but I didn't want to sacrifice any of my finished pieces for that experiment. Also, I didn't want to wait for half a year before I would see a result (because that's how long you should wait at least before varnishing an oil painting). However, an experiment with acrylic paints using earth tones should be close enough to get the information I wanted. I created a triptych and then varnished the three pieces separately to determine how different they look with the different varnishes.

Overall result: There is much much less of a difference between then three pieces than if they had been on regular (smooth) canvas. Even with the (very) glossy dammar varnish the painting was nowhere close to being as glossy and reflective as you would see on a smooth canvas. Here is a photo of the triptych as a whole (before varnishing)



Now, to show the differences between the results I photographed a corner with two of the pieces next to each other and I also photographed them at an angle against sunlight to check for glare. There is a noticeable difference between matt and glossy, but the differences between matt and satin or satin and glossy are less then you would expect. Also, I noticed that varnishing didn't intensify the colors as much as it would on a smooth canvas. That's at least my observation.

As result I'd say: varnishing on burlap (at least when the burlap is as loosely woven as in this example) doesn't make a huge difference in the look of the piece. I assume it still protects the painting, but I wouldn't be surprised if there was less protection because there is no continuous film covering the piece.







In another experiment I noticed on tighter woven burlap the effects of varnishing are much closer to varnishing on regular canvas. The photo shown below is from painting on burlap where there are no "pores". This piece was sprayed with the "Satin" varnish and it definitely is much more glossy then the other piece I sprayed with Satin varnish:



I used Winsor&Newton spray varnishes: Matt Picture Varnish, Satin Picture Varnish and Dammar varnish. Overall result: "I depends" ;) In general I think I will varnish my burlap pieces and I'll probably use Matt or Satin. Even if the glossy varnish creates only limited glossiness the matt or satin finish just seems to fit better for the burlap pieces that I do.