Tito: Is there a "typo" in your question? What is can "unplained" table?
Please post pictures so I can see the table close up so I can give advice.
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Are you asking about an unstained kitchen table? You'd give it a sanding, stain it if you'd like, then seal it up with a water based polyurethane sealer.
It depends on what needs repairing. If the top is bare wood, you can try sanding out the damage. If some sort of oil has gotten into the pours of the wood, this may be difficult. Tell us a little more.
Do you mean unfinished wood? If so then sand it, stain as you like and then apply a water based polyurethane sealant.
You can sand it, if it isn't terribly in need of planing. I did one and the wood was very pretty. I didn't stain or paint, just 3 coats of polyurethane.
What exactly is wrong with the table that needs to be fixed?
Posting a picture of the table would better illustrate the problem.
Hi Tito: Is it wavy? If so, you might be able to take it to a woodworking store and they might be able to plane it evenly for you. Or, you could put a thick piece of acrylic over the top with rubber feet in the corners and the middle of the edges to keep it from scooting around. Paint or stain the table top and you should be good to go.