dealing with wood discoloration after surface treatment
January 16, 2021 1:48 PM Subscribe
I have a wood tabletop (IKEA Gerton) that I'm going to use as a work surface. After sanding from 120 to 180 grit and applying a preliminary coat of water-based polyurethane (Minwax brand clear satin wipe-on) several large light spots appeared on the wood surface. What may have caused this, and can it be fixed?
Here are pictures of the tabletop after the first coat of water-based polyurethane.
The silhouettes are from various objects resting on the tabletop before sanding and applying the finish. Would they have trapped moisture in the wood or something? Should I sand it down and let it sit for a few days before beginning again?
Here are pictures of the tabletop after the first coat of water-based polyurethane.
The silhouettes are from various objects resting on the tabletop before sanding and applying the finish. Would they have trapped moisture in the wood or something? Should I sand it down and let it sit for a few days before beginning again?
To make sure you're sanding evenly and sufficiently, draw stripes across the work surface in pencil. When they're gone, you know you've done it enough. Probably do it once to get the poly off, and again on the bare wood.
posted by supercres at 2:20 PM on January 16, 2021 [1 favorite]
posted by supercres at 2:20 PM on January 16, 2021 [1 favorite]
I don't know how much you know about sanding.
The marks are pretty obviously from the objects placed on the surface, in one way or another. They could be water, air exposure, or light. You need to sand down below them. I'd assume that they don't go very deep into the wood.
Generally speaking, for reasons I won't go into here, you can double the grit each time, so 180 - 320 - 600, if you want to go that high.
I find you get the best results using a sanding block, so you don't get high and low spots, and so that if part of the wood is softer than the rest - which isn't unusual if something has sunk into it. I usually use a chink of wood wrapped in thin rubber or leather, though you can buy chunks of rubber for this. I've also used random pieces of wood, cans of sardines, and paperback books.
Your finish looks pretty nice aside from the marks, so don't give up.
posted by AugustusCrunch at 2:50 PM on January 16, 2021
The marks are pretty obviously from the objects placed on the surface, in one way or another. They could be water, air exposure, or light. You need to sand down below them. I'd assume that they don't go very deep into the wood.
Generally speaking, for reasons I won't go into here, you can double the grit each time, so 180 - 320 - 600, if you want to go that high.
I find you get the best results using a sanding block, so you don't get high and low spots, and so that if part of the wood is softer than the rest - which isn't unusual if something has sunk into it. I usually use a chink of wood wrapped in thin rubber or leather, though you can buy chunks of rubber for this. I've also used random pieces of wood, cans of sardines, and paperback books.
Your finish looks pretty nice aside from the marks, so don't give up.
posted by AugustusCrunch at 2:50 PM on January 16, 2021
This thread is closed to new comments.
Also, 180 is still pretty coarse. I'd do 240 and then 320.
posted by jonathanhughes at 2:06 PM on January 16, 2021