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Varnish Issue

Oct 13, 2015
Catalina C309 Stank Paw Slough
Out if the blue, having prepared the surfaces and varnished…this happened on a pretty hot day.

any ideas?8F1A4EE6-FAB3-4C4F-A07E-B41790DD3118.jpeg6919979C-6826-404A-8C17-C8E394B93C20.jpeg
Jan 19, 2010
Hunter 26 Charleston
Looks like moisture in the wood evaporated and lifted the varnish before it could fully dry. I've only ever had this problem with polyurethane in the sun. Varnish usually can breath a little.
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Oct 22, 2014
CAL 35 Cruiser moored EVERETT WA
Man, hate when that happens.

The wet wood or wood not completely cleaned statement of @rgranger seems most plausible.

There are different types of varnish. Oil and water do not mix well. I have had best results with the Total Boat products.

Gleam 2.0 (excellent for on deck wood - oil based clean wood, use a rag with denatured alcohol as final cleaning before first coat. Repeat coats every hour up to 3 a day no sanding.)

Halcyon Water-Based Marine Varnish
A durable one-part water-based marine varnish dries to a UV-stable, gloss finish that accentuates the wood grain and improves clarity—even after multiple coats.
I am using it inside to give new life to the internal woodwork of my boat.
Jan 11, 2014
Sabre 362 113 Fair Haven, NY
Out if the blue, having prepared the surfaces and varnished…this happened on a pretty hot day.

any ideas?View attachment 197215View attachment 197216
Mostly likely some contamination on the wood and/or some moisture in the wood.

This is repairable. Sand the area down to a good solid surface, can be bare wood or existing good varnish. Feather the edges. Meticulously clean the surface try using mineral spirits first to remove any grease, then denatured alcohol. Build the coats back up following the manufacturer's directions.


Oct 21, 2009
hunter 38 Monaco
Most likely something/somebody/whatever touched the varnish when the surface was dried but not the underlying layer. The movement pushed the top layer to the left and created the shear to the right and the uplift to the left. Just redo it.
Feb 11, 2017
former Tartan 30 New London, CT area
I changed my winch pad areas to Trex (as well as hatch trim, hand rails, and transom trim). Only exterior stuff that stayed varnish was stuff I could bring home over the winter. Oh yeah, toe rails got painted to match the Trex.