And thinning even further would allow you to spray via HVLP, but that’s definitely not my favorite way to apply an oil-based varnish. Thinning by about 10-20% will make brushing significantly easier. So one way to significantly improve the workability of your urethane is to thin it with mineral spirits. It can be like trying to lay down an even coat of corn syrup. Most of the trouble comes from the fact that the urethane solution is so thick. Sponge brushes are certainly another option, but the results are not always a significant improvement. You need to use the right brush and it takes a little practice to get the technique right. Polyurethane, whether it’s an outdoor or indoor formula, takes a little finesse to apply without bubbles or brush strokes. To thin or not to thin?” The Power of Dilution Is it possible to thin Helmsman and spray it with an HVLP gun? There is a Helmsman spray can available but I have so much Urethane left over. After 4 coats, I have managed to sand it down fairly flat. I know it’s barely noticeable but I absolutely abhor brush marks. I am applying it with a quality brush but I still get brush marks and hi-low points, also tried a sponge brush with same results. It’s a one piece flat door - no recessed panels. “I am using Helmsman Spar Urethane to refinish the front door of our house. This article was inspired by a question from Jeff.
