Written by: Matt Shields
Even after proper kiln-drying and varnishing, wood still responds to temperature and moisture. Wood will bend and twist, and cracks will get longer and wider. Untreated cracks can cause a flat tabletop to warp or, in extreme cases, separate from the bases or legs. The most effective ways to deal with cracks in wood are, in order: remove, replace, fill, and patch.
Remove: If cracks occur near the ends of boards, cut them out. Mark the end of the visible crack and add a few extra inches to the cut-line, in case it has extended beneath the surface. Cut with miter saw or crosscut sled on table saw.
Pro: Quick removal. Prevents warping.
Con: Lose some material.
Replace: If cracks occur in the middle of boards or slabs, consider routing them out and replacing with a bowtie or other inlay. For cracks that go completely through the board, consider inlaying both sides.
Pro: Prevents warping. Looks impressive.
Con: Timely. Requires router, template, chisels, or other additional tools.
Fill: Epoxy is often used in combination with inlays, but may be used on its own to save time. Best to use when the cracks do not fully penetrate the entire board.
Pro: Seals wood fiber and fills void in one application. Easy DIY color-matched.
Con: Expensive. Messy. Requires blowtorch for bubbles. Short epoxy shelf-life.
Patch: Wood putty should be used sparingly for the tiny cracks that epoxy won’t flow into. Read the directions on the product. While most putties are applied right before varnishing, some new products on the market are applied afterwards. Cyanoacrylate (Superglue) can also be used, but may be incompatible with certain varnishes or may discolor the surrounding area.
Pro: Cheap. Very fast application. Many colors available. Long/indefinite shelf life.
Con: Cosmetic fix only. Doesn’t prevent crack from worsening very much.
When in doubt, call The Urban Wood Lab Store for suggestions at 262.902.8950.
Matt Shields is a fourth-generation woodworker who specializes in design and creation of mid-century and mixed-media contemporary styled pieces. When he's not sharing his expertise with customers at The Urban Wood Lab Store, he can be reached at Hyde Woodworking.