Most wood tables have a finish that protects them from pen mark stains. Even so, ink that sits for too long on a wood finish can eventually penetrate the wood and become increasingly difficult to remove. Remove pen marks from wood tables as soon as possible to keep the surface from showing age and garish stains.
Blot the wood table with a damp rag to remove as much of the pen mark stain as possible. Blot the wood gently, and avoid rubbing, as pressing the ink pushes it farther into the wood finish.
Sand the pen marks gently with a fine-grade sandpaper. Wipe away residue from the wood with a clean rag.
Mix 2 tbsp oxalic acid with 1 pt. of warm water in a bucket. Using a medicine dropper, place two to three drops of the acid on the pen mark. Allow the drops to remain on the marks for two minutes, then wipe from the wood with a damp rag. Apply additional oxalic acid solution if the pen mark remains, and again clean it from the wood after two minutes.
Apply a furniture polish to the wood table after removing the pen marks. Wipe excess furniture polish from the table with a lint-free towel.
Use caution when working with oxalic acid, as the solution is highly toxic.