Success with SlabsComments (0)
This article is from Issue 79 of Woodcraft Magazine.
Order of Work
- Surface and smooth the slab.
- Remove the bark and clean up the edge.
- Stabilize splits and patch defects.
- Fill voids if desired.
Finding the right slab
Many mills (and some Woodcraft stores) carry slabs. Also, try checking an online supplier. (See page 64 for sources.) We cut many of our own slabs with a portable chain saw mill, but realize that it’s no small undertaking to slab your own lumber.
The thickness of a candidate slab is important, especially if the edge is to be the focus. For tabletops, look for something 1-1/2" to 2-1/2" thick. Thinner pieces are fine for shelving and small projects. As for shape, be aware that designing a base for a wildly dramatic slab can be challenging, as it usually doesn’t pair well with typical leg-and-apron construction. Instead, consider spindle legs, steel bases, and trestle configurations, mocking them up first using cardboard and scrap wood.
Inquire if a slab has been kiln-dried. Many are simply air-dried because they don’t fit well into small kilns. Look for a milling date as a drying-stage reference. As a general rule, any hardwood should air-dry at least one year for each inch of thickness, but use a moisture meter for an accurate assessment.
Flattening: A good job for a jig
Flattening a large slab presents an unusual challenge, even for woodworkers who have a large planer or thickness sander, because one face of a slab still needs to be flattened before feeding it through one of these machines. You can hand-plane a slab, or try using a portable belt sander, but both approaches are very labor-intensive, and you can’t be too fussy about the results. Many shops, like ours, flatten slabs using a router sled. (See page 48.)
Peel and preen the live edge to highlight its beauty
Debarking the slab is important not only to expose the edge and evict any live or dead bugs, but to remove residual bark that might otherwise eventually fall away, soiling someone’s carpet. The type and tenacity of the bark determines the tool used to remove it, whether it be a drawknife, screwdriver, or gouge. After debarking the edge, remove any residual detritus or fibers using a wire wheel. Then finish up the edge using sandpaper to soften any sharp or rough spots and to ease the edge where it meets the slab surfaces.
Keep splits in check with decorative reinforcements
End-checks and other splits are common characteristics in slab furniture, and shouldn’t necessarily be cut away as “defects.” All the same, they do need to be reinforced to prevent further movement. The traditional approach is to span a check by inlaying a “key,” often shaped like a butterfly. Here at Lohr Woodworking Studio, we use bone-shaped keys instead for a custom touch. Whatever shape you choose, orient the grain lengthwise, and make the piece wider at its ends than at the center for mechanical strength. Bandsaw the key from stock that’s about 2/3 the thickness of the slab, and use a sanding drum to smooth the edge of a bone, or a chisel to clean up the edges of a butterfly. Then install the key as shown.
Dealing with defects: Fix with Dutchmen or epoxy
Learning to love flaws doesn’t mean you shouldn’t be discerning about those that clearly cross the line into defect territory. For example, you’ll want to patch sections where growth layers are peeling up (often induced by windshake in the living tree). Loose or broken knots should usually be “replaced” with a patch or filled with epoxy. As for voids, either leave them be or fill them with epoxy.
Installing a patch, or Dutchman, is identical to installing a key, except that the patch typically doesn’t need to be very deep. The key to success is selecting Dutchman material that matches the grain patterns and color of the area surrounding the defect. Instead of square patches, we typically create curved, organic shapes that better mimic grain flow. When replacing a knot, favor a patch that matches the tone and color of the original. When using epoxy, follow the procedures shown here. (Note that 5-minute epoxy can be used for small voids and keys, but you’ll want to use a slow-set variety for larger voids.)
Dunk the crumbles. Press bark crumbles into the wet epoxy mix. After sanding, this treatment will mimic the color and texture of a natural bark inclusion instead of just looking like epoxy filler.
Finish up with oil and varnish
We’ve found that the best approach to beautifying and protecting slabs is to first slather the entire piece with boiled linseed oil to “pop” the color and figure. After wiping off the excess, let the oil dry for 5 days before applying the first of about 5 coats of a satin-sheen wiping varnish to both sides. (Avoid a gloss sheen because it’s too difficult to rub out edges afterward to subdue the shine.) Where necessary, use an artist’s brush to get the finish into unfilled checks and other splits. Scuff-sand the flat surfaces between coats, and rub out the final coat using steel wool lubricated with mineral spirits to eliminate dust nibs and create a consistent luster.
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