MITRA Forum Question Details

It is not absolutely necessary to frame and glaze watercolors or watercolor-like acrylic dispersion paints on paper. It is, however, generally recommended as these types of paintings remain quite absorbent which allows dust and grime to be imbibed into the surface. It can be difficult to remove this grime at a later date.

I would not recommend varnishing works like this unless you are trying to achieve a specific effect. Traditional solvent borne varnishes will saturate and darken the exposed paper, shifting the whole balance of the picture.

​Our recommendations would largely depend on how you are planning to display your work and on your motivation for varnishing. Solvent borne varnishes indeed soak into paper more than water borne mediums or paints and therefore darken paper more and change color values. For acrylic paintings, Golden generally recommends the application of an isolation coat which is a clear acrylic dispersion medium. This would seal the absorbency of the paper and prevent the subsequent varnish from penetrating into the paper. Such an isolation coat cannot be removed from an acrylic painting and therefore it is advisable to practice its application first on a sacrificial piece which contains the same materials as your artwork. That will also allow you to judge whether the aesthetic changes caused by isolation coat and varnish are acceptable to you. 
Mirjam (Golden Artist Colors)