How do I properly paint wood for a smooth lacquered surface?

Hello,

I built a closed staircase. For the risers, I used simple 19mm 3-layer boards from the hardware store. I filled, sanded, and painted them white. It looked pretty good when I installed it. Nice, even, smooth painted surface. I didn’t want any wood grain or anything like that.
Now, in some places, the grain is slightly visible again, and in others, the paint has even cracked along the grain.
What did I do wrong? How should one actually do this? Is there still a chance that I can correct the risers while they are installed?

Best regards

Hi,

the problem is quite typical with 3-layer boards or generally with wood-based materials that have a stronger grain. Even if you have filled and sanded, the wood continues to work. Moisture, temperature, and mechanical stresses cause the fibers to slightly raise again or the varnish to crack due to tension. Especially with simple boards from the hardware store, the surface is often not quite ideal for a mirror-smooth varnish finish.

Usually, it can still be fixed afterward, but you need a bit of patience. It’s best to first smooth the cracks and visible texture with fine sandpaper, then apply a really good sealing primer or isolating primer that helps seal the wood and cushions the tensions a bit. After that, sand again and apply a high-quality varnish on top, preferably with intermediate sanding. When the board is installed, it requires a bit more effort, for example good masking all around and a small roller or a fine brush for the corners, but it is doable.

If you want to be on the safe side, use a PU varnish or acrylic varnish with high elasticity, which remains stable even with slight movement in the material.

Best regards

Super thanks for the answer and the tips. It will probably be a winter project sometime in 203x ;). Maybe I will prime the back side with the sealing primer earlier, so less moisture gets into the board and it works less.