Recently had the deck at our cabin re-finished with a semi-transparent stain. While applied beautifully, we noticed that when the wood gets wet, the water beads up as expected but when the water eventually dries it leaves dark brown rim marks that are easily visible against the light gray color of the deck. It makes the deck look stained or dirty. It almost appears like someone has spilled coffee or tea and didn't bother to clean it up. I originally thought the issue might be caused because the wood of the deck was old/dirty/had residue from the trees, etc. but when I put clear tap water on my color sample board at home the same thing happened and this piece of board hasn't been outside since it was part of a tree.

When I shared my concerns with the manufacturer of the stain their reply was that the wood is now so well sealed that any sediment in the water is now prevented from penetrating the wood and thus is forms "rings" on the surface when it dries.

Any insights regarding what might actually be going on would be greatly appreciated.

dust rings. if they wipe off with a damp cloth, time to clean the sky.

around here, big pollinators dust us yellow, so that's why I'm thinking dust. YMMV.