To waterproof the wood that will be placed outdoors, choose a marine varnish, which contains UV absorbers to resist sun damage. For interior use on side tables and coffee tables, SPAR varnish is a good choice for resisting annoying cup rings. Using natural oil such as linseed oil or walnut oil is a fantastic way to waterproof your table and protect it from the sun, mold and insects. Whichever option you choose, you'll have a sturdy, waterproof table in no time.
Start by staining the wood with a waterproofing dye. This will help protect the wood from moisture and will also give it a protective layer. Once the stain is dry, apply a layer of sealer to the top. The sealant will have to be reapplied every few years, but it will help keep the wood in good condition for longer.