Used Helmsman Spar Urethane on a garden bench last year. Still looks good. Here’s what I learned.
What It’s For
Outdoor wood that needs to look nice. Decks, furniture, doors. Not structural stuff – that needs different treatment.
UV protection is the main selling point. Regular poly yellows and cracks in sunlight. This stuff doesn’t. At least not as fast.
Surface Prep
Sand to 180. Don’t go finer – the finish needs something to grab. Wipe with mineral spirits to remove dust and oils.
Bare wood is best. If there’s old finish, strip it or sand it completely. Helmsman over failing finish just traps the problem.
Application
Thin coats. Cannot stress this enough. Thick coats bubble, stay tacky, never cure right.
I use a foam brush. Cheap, no brush marks, throw it away after. Natural bristle works too but requires more skill.
Three coats minimum for outdoor. Sand lightly between coats with 220. More coats on end grain and tops – water hits these hardest.
Dry Time
Touch dry in a few hours. Recoat in 24. Full cure takes a week or more. Don’t put anything on it until then.
Humidity matters. High humidity means longer dry times. I’ve waited three days between coats in summer.
Maintenance
Annual light sanding and one fresh coat keeps it looking good. Skip this and you’ll be stripping in three years.
