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Reasons to Varnish


Bathed in Sunlight 24X36"

Acrylic Painting (cropped)

Reasons to Apply an Isolation Coat Before Varnishing


  • Binding washes, drybrush and paint to the support's surface.
  • Evening out the sealing of a surface so that a later varnish can be applied with a consistent level of reflectiveness.
  • Provide a permanent layer that will protect the painting and allow an archival varnish to be later removed (and replaced).  The removal process involves additional chemicals, currently NH3aq or special solvents for Mineral Spirit Acrylic (MSA) varnish which are intended to act only on the archival varnish but may also damage the paint underneath if allowed direct contact.
  • At this stage, the painting may look richer with deeper darks.  The painter may wish to do additional work on the painting knowing that its appearance will change with any clear coating. Recent work should then be recoated after a week of drying.

Any one of the above benefits may be sufficient cause for applying an isolation coat.


Reasons to Apply a Varnish to a Painting


With or without the isolation coat the painting will appear less chalky, dry and flat.  The darks will look darker and richer.  Some colours may come out at the higher and lower value ends.

Diminish or eliminate glossy and matte patchiness.  For an acrylic painting this will depend on your pre-coating with an isolation coat(s).  For oil painting, this will rely on how well the suface is sealed - the sum result of good priming, wet impimatura and oiling out.


Many of the mediums used in an acrylic isolation coat and at times, the acrylic paint itself, are sticky and can hold a static charge causing the surface to attract and retain airborne dust particles or smoke (from an increasingly burning world).  However, a good varnish is a different matter, often having been modified not to collect dust or be sticky.  Damar mixtures for oil painting varnish are sticky - no such benefit there.

A satin or matte varnish can reduce the glare produced by light shining upon a painted surface.

Protect the painting from mold, smoke, cooking grease and reactants or oxidants found in the air.  Or the sticky fingers of small children from your white trash neighbours.  In the case of a varnish containing UV barriers (inhibitors), from the ionizing effect of ultraviolet sunlight. A final top coat of varnish offers a surface which can be cleaned without damaging the painting.