I’m not familiar with spraycan varnishes available in the US but unless you’re sure about what they are I would be wary about using them on an acrylic painting. Please refer to the relevant test reports/certificates and the Technical Data Sheet for information on certified products and configurations.

From Winsor and Newton, an excellent range of aerosol varnishes (seven in all) covering most of the key media areas where artists are involved.For certain works glossy finishes just don’t look ‘right’, so matt or nearly matt might be most appropriate; I often think that small paintings look a little odd when too glossy for example, the gloss seems out of scale with the work somehow, so size might be a deciding factor also. If you apply a single coat and you’re getting sufficient coverage you’re probably applying it too thickly. Spirit-based varnishes are easier to apply and not prone to humidity- and temperature-related changes in surface tack and tend to be harder and tougher, so are much better at resisting dust, scratches and other mechanical abrasions.

They won’t work out cheap, especially for a large area, and they will yellow and darken over the years but if nothing else works out they might be worth a shot. I used to just use gloss medium as the varnish but was told that coating the surface of the painting with that was a bad idea since it can not be removed. If you don’t get anything more helpful and since the piece can’t last forever, you might consider trying something old-fashioned like an oil/resin varnish (linseed oil/copal for example).

Two or three coats is usually sufficient, with each each successive layer applied at right angles to the one before.

Dries clear to a flexible, non-tacky, hard surface, increases brightness and color saturation, adjusts and unifies surface sheen and improves surface durability. Suitable for application over acrylic paints both interior and exterior, the coating will also protect against UV damage. I have always applied a thin coat of medium as an isolation coat under whatever varnish I used since reading the advice many years ago, all the current advice seems to confirm it.When coating surfaces finished with a coloured varnish, a maximum of 5% of the coloured varnish can be added to the product if necessary. A thick coat will take longer to dry, may dry cloudy, may drip or sag during application and has a greater chance of showing brush strokes when dry. Grumbacher is a spray for both oils and acrylics, and is the brand I currently… as you can probably guess by the name, it’s not cheap. I’m looking for a smooth, wet, sexy, high-gloss look for the finished surface of some paintings but didn’t want to go the polyurethane route.

This means if there is a problem like scratches, embedded dust/dirt or discolouration it might be impossible to rectify without damaging the painting beneath.When finished spraying, turn can upside down and push spray button for 5 seconds to prevent clogging.