Contrast varnish with oil, which doesn’t dry hard, and with shellac, lacquer and most water-based finishes, which don’t cross-link. Two-part clear polyurethanes are known for superior UV resistance and scratch resistance compared to traditional varnishes, but they have shown mixed results when applied directly to wood. Another professional ‘trick’ with spar varnish is to apply it to all uncoated wood surfaces that are to receive a coat of paint. Success secrets: Drying oils and varnishes are compatible with each other when mixed, so you can create your own blend by combining equal parts of boiled linseed oil and any oil-based varnish.
After application it can penetrate deeply into the wood because of its consistency and protect it from the inside, so to speak. If this still doesn’t work then a light sand with a fine grit sandpaper may work but you are getting closer to risking removing some of the Varnish. If there is a lot of thick varnish to be removed you could resort to a hot air gun and a hook scraper or if you are feeling brave a blow torch. Both linseed and tung oils are penetrating finishes – which means that they penetrate into the fibers of the wood and harden within the wood. Wet sanding, which can remove a whole varnish coat very quickly is far less likely to cut into the poly as aggressively.
I am certainly no specialist in the area of siding, but I am sure a good quality spar varnish would indeed protect adequately. Just wipe on boiled linseed oil with a soft cloth or flood it on until you’ve saturated the wood surface. Let’s start off by talking about what goes into manufacturing traditional, ‘oil based’ (solvent based varnish). When the wood changes dimensions, it forces the varnish to stretch and shrink in order to stay attached.
The old way of varnishing, the traditional” way, is to sand the topcoat layer by layer to obtain a mirror-smooth varnish topcoat. Hi Dom, if it’s for a longboard and you’re not intending on removing the varnish in the future for aesthetic reasons I would be tempted to use a yacht varnish. I put one coat of primer over it before painting the scenes with Sherwin Williams’ exterior latex paint (can’t remember the name of it but it’s very thick). Mix them together to match the stain of the wood and with an artists brush or a toothpick touch up all the paint that is showing. A good finish starts with sanding the bare wood with a 100-grit sanding sponge and/or paper.
I just self-study and been reading your articles 🙂 I need your help.. Its just recently that I started making big artworks (3×4′, 4×4).. My problem is.. the gloss varnish I applied didn’t look even. As for woodworking shows, I’m a relatively new woodworker and I learn something every time I watch Wood Works and New Yankee Workshop. For boat varnish work, always sand along the direction of the grain of the wood and not across it, so it really needs to be done by hand.
Someone gave me this tip when I built my wife a bookcase: instead of using fine steel wool or sandpaper, I used brown paper (from a brown paper bag) on my sanding block, after each coat of varnish. Gel varnish is alkyd or polyurethane varnish made into a thick gel consistency similar to clear glaze so it doesn’t run on vertical surfaces. However, the penetration of the oil tends to intensify the natural beauty of the wood. For instance, Minwax (Helmsman) Spar Varnish shows 3% pigments and 1.6% Ethyl-vinyl acetate by weight.
In almost all cases, thin-coat varnish is solvent-based, in that something other than water is used to dissolve it. Thick-coat varnishes can contain solvent or be water-based. Pure oil is a surprisingly good alternative to a solvent-based lacquer or varnish: Pure oil contains no solvents and comes from renewable resources. Bartop is tougher while spar varnish gives you a mirror finish thats a little less scratch resistant. How long it takes to do will really depend upon how well you can organise your life to fit around the drying times of the varnish. Your polyurethane wood floor finish is not going to look perfect on the first coat.