It is a good idea to apply an isolation coat on your paintings before varnishing.
- I like that some varnish are meant to be removable. It is a good thing because if you change your mind after a painting has been varnished, you can take off the varnish with mineral spirit. This would not work with acrylic based varnishes which are permanent. The risk when taking off the layer of varnish is to remove some of the paint as well. To avoid that, you can seal your painting with an isolation coat before applying the varnish.
- I am also sometimes a bit nervous about the way varnish can react with mixed media and want to make sure nothing is going to happen with the varnish or smudge when I apply it, an isolation coat will prevent that to happen.
Here is how to apply an isolation coat
Once your paint had enough time to dry thoroughly, I always recommend you apply a layer of spray fixative. You have to do it outside as you are not supposed to breathe that product. The fixative will fix any medium and prevent any smudging from happening.
In a container, pour a small quantity of acrylic medium.
Add about the same quantity of water. Try to not go over 50% water as this is the ratio at which the acrylic starts loosing its binding properties.
Mix the water and the acrylic medium very well in your container. You will get a milky liquid that will dry transparent.
Apply this mix with a soft brush.
Try not to go over the same area twice, this is very important as it could make some of your acrylic or ink smudge. Try to go fast and in one go.
Look against the light to see if you missed any part.
At this point I like to let the painting dry overnight. Then you are ready to apply a layer of varnish. I recommend either Liquitex soluvar or Gamvar by Gamblin. Both are removable with mineral spirits and both are suitable for both oil or water-based media.
Again when varnishing you can look against the light to see if you missed any part. Let the varnish dry and you are done!
Acrylic and mixed media on Claybord
12 x 12 inches