A few water drops left unnoticed sitting on a front can soften the varnish underneath and when wiped off eventually, the top layer of the varnish has been removed and little shallow craters remain.

As with all varnish work, it’s quick enough to blend in the colour but what does take time is building up the craters to the same level as the surrounding varnish by applying filler varnish first and then scraping it to the same level as the original varnish before blending in the colour with retouch.