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Trying to just add another coat of Spar Varnish to bed wood (I’ve never used this before) and I keep getting random dull spots. I have sanded the whole floor and allowed it to dry at least a day before another coat. Using Spar because that’s what was on it just old from the original restoration it just had a few spots that had peeled. Any advise?
Last edited by 53Hippy; Jan 28, 2026 at 02:24 AM.
Reason: Add to post
I have had trouble putting any kind on wood until I found out that most of my trouble was using any kind of a bristle brush. For me a foam brush and keeping it wet worked out better. Good luck
I am not a wood expert, some of the common things are wood absorption rate, humidity, contaminated wood (ie oils from your hands after sanding etc).....I had a problem one time with an interior door and just gave up......here is some advice (not mine) from the experts on the internet, take it for what it is worth.
Ah, the classic “why does my varnish hate me right there?” problem 😅
Random dull or flat spots with spar varnish are very common. Here are the usual culprits, from most to least likely, and how to fix them.
The most common causes
1. Uneven absorption (end grain or porous spots)
Wood doesn’t absorb evenly. End grain, softer grain lines, or repaired areas soak up more varnish, leaving those spots flatter.
Fix
Seal first: wipe on a thinned coat (50% spar varnish / 50% mineral spirits).
Let it dry, then lightly scuff sand (320–400 grit).
Continue with full-strength coats.
2. Contamination on the surface
Even tiny amounts of:
Silicone (from polishes)
Oil/grease from hands
Wax residue
Shop dust or cleaner residue
will cause varnish to pull back and dull.
Fix
Wipe down with mineral spirits or naphtha before finishing.
Use clean, lint-free rags.
Don’t touch the surface after wiping.
3. Over-brushing or uneven brushing
Spar varnish sets slowly, but if you keep brushing areas as they start to tack, you knock the gloss down locally.
Fix
Lay it on → tip it off → walk away.
Use long, continuous strokes with the grain.
Resist the urge to “fix” spots while wet.
4. Humidity or temperature issues
High humidity or cold temps can cause partial curing or micro-blushing, leaving dull patches.
Ideal conditions
65–80°F
Humidity under ~70%
No moving air directly on the piece
5. Old or poorly mixed varnish
Flattening agents can settle, or the varnish may partially polymerize in the can.
Fix
Stir slowly but thoroughly (don’t shake).
If it’s thick or stringy → strain it or replace it.
How to fix dull spots that already happened
Quick fix (usually works):
Let the coat fully cure (24–48 hrs).
Lightly sand with 320–400 grit just to even the sheen.
Apply another thin coat, thinned ~10–20%.
If spots keep coming back:
Do a wash coat (very thin varnish or dewaxed shellac).
Then recoat normally.
Pro tip for spar varnish
Spar is softer and more elastic than interior varnish, so it exaggerates absorption differences. More thin coats beat fewer thick ones every time.
Should I dilute the varnish with mineral spirits? I keep seeing to dilute at first few coats but was thinking that this being a top coat I wouldn't need to? Will try the foam brush on next attempt and seems like I may have been over working the finish when applying. Updates to come. Thanks for tips guys.
I might be seeing things wrong, but they look like cloudy spots where the old finish remained and was coated over.
If the old finish is not completely removed, the new finish can soften the “lift” the old finish causing cloudy/hazy spots. It is best to remove the old finish completely and start new.
Wiped it down with mineral spirits before using a foam brush with a 50/50 mix of mineral spirits and Spar Varnish! The stuff you see on the finish is actually a reflection of my jeep top hoist on the ceiling! Couldn’t be happier thanks everyone!!!
Last edited by 53Hippy; Jan 28, 2026 at 04:20 PM.
Reason: Adding details
