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I have the slab shown in the pics below. During the drying/curing process it developed many micro cracks a few larger (some through-slab) cracks. These cracks exist on both the main surfaces and on the live edge itself (one or two with some minor instability...should enough pressure be applied).

I've worked on one slab before this so I am a novice as of yet.

I love the character the cracks add to the slab and am curious about two things w.r.t. using 105/205 West System resin as to fill cracks on it:

1) Will filling cracks with resin visually add or detract?

2) Would filling with 105/205 West resin add any real strength? I just bought the slab and while it seems thoroughly dried, I'm uncertain as to whether new cracks will inevitably form due to the type of wood that it is.

3) How does one fill the live-edge side of the slab with resin while avoiding bleeding of the resin into the wood surrounding the cracks? The bleeding normally of course needs heavy sanding to remove, but I'm afraid of this heavy sanding due to concerns of destroying the feel/look of the live edge.

4) General thoughts on how best to approach this slab to bring out its full beauty/potential?

Note: I've investigated this similar SO post, but the answer seems rather unhelpful as far as how to best manage edge-resin-fills: Can you fill cracks in the side of a live edge slab

Thanks!

enter image description here enter image description here some cracks on edge at far that can't be seen

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Just read over my Answer and TL;DR warning I guess!

Will filling cracks with resin visually add or detract?

Totally a personal call. Some people don't mind open cracks (somewhat depending on how open they are) while others seem to need any and all cracks.

Filling cracks opens up a range of possible decorative choices, from the very common dark brown or black to something that will stand out, to make more of a feature of them, so strongly coloured, filled with crushed semi-precious stones like turquoise, or metal powders including stainless steel, nickel, brass or bronze.

Would filling with 105/205 West resin add any real strength?

Not in surface checks. Yes for cracks that run through, but butterfly keys or anything similar probably add greater reinforcement that is more likely to endure in the long term.

Note that if you don't like the look of butterfly keys or any alternatives they can be installed on the underside and not the top.

I just bought the slab and while it seems thoroughly dried, I'm uncertain as to whether new cracks will inevitably form due to the type of wood that it is.

Best to adopt a wait-and-see position and leave it in your working conditions for a while. If your workshop has lower humidity than where the slab was last stored (reasonably likely) then I'd bet more cracks will show, or one or two of the existing ones will open up further.

Now how long to wait... well that's partly up to how long you can wait, but given the thickness I would suggest at least a couple of months.

How does one fill the live-edge side of the slab with resin while avoiding bleeding of the resin into the wood surrounding the cracks?

A good tip is to lightly finish the surface of the wood around the fill site1. Excess epoxy won't penetrate much or at all and will be much easier to pare, file, scrape or sand from the surface as well. Shellac is probably the best choice for this, although you can use other finishes and they'll work equally well shellac can be applied very accurately by brush and dries really quickly so virtually no wait time before you can proceed to the next step.

The bleeding normally of course needs heavy sanding to remove

Just to note, on any flat surfaces planing or scraping are other ways this can be done and it's easily argued are better choices for the usual reasons (if you need just one good one, speed alone is enough to prefer them to sanding).

While some sanding of the surface is almost certainly going to be needed regardless of the approach taken to get the majority off it reduces it to a minimum which is a good general position to adopt.

General thoughts on how best to approach this slab to bring out its full beauty/potential?

Oil or an oil finish are the ideal finishes to bring out the full beauty of wood grain. Even when using shellac (including full-on French polishing) previous treatment of the wood with oil is common as it increases contrast and enhances chatoyancy to the greatest degree, often now referred to collectively as "popping the grain".

If you'll be finishing in polyurethane varnish, or any other oil-based varnish, there's probably no benefit to oiling the wood in advance, but you'd should do a test to confirm this. Use the underside for any tests like this, or an offcut if there is one.


Just as a closing comment, this doesn't look like it was dried well and it's that which directly led to many of the cracks (one or two are often inevitable). If other pieces of similar wood from the same source show the same defects2 I wouldn't buy any from them again unless there's a price consideration.


1 You may have to treat the whole area, remembering that any wood treated this way will be partially sealed so any penetrating finish used for final finishing won't colour it the same as untreated wood around it.

2 While the current taste often sees cracks as 'features' it shouldn't be forgotten they are defects and good, careful, drying methods largely avoid them. Since cracks are defects they should be a factor in pricing so look for a discount when any number are present.

  • Very informative! I'm curious - how do you recommend sanding/filling/finishing the live-edge (bark edge) side of the slab? You mentioned to lightly shellac and then resin fill. My assumptions are: first coat the entire edge with a single shellac coating, resin fill (top-side presumably?), use something like 400-1500 grain sandpaper and/or polishing cloth wheel on a drill, followed finally by an oil finish (or varnish)? If I weren't to resin fill, just do the 400-1500 sanding (or cloth wheel?) followed by oil/varnish? Sorry if redundant, I'm paranoid about ruining the slab's live-edge :) – John Cast Nov 22 '17 at 8:22
  • SE discourages follow-on queries so this isn't ideal, and also this is a lot of questions! But 400 is far too fine to start to remove excess resin from a fill, you need to get the bulk of it off by whittling, paring or filing first, then move to scraping and/or sanding. Much existing info out there online on finishing off live-edge surfaces so once you are back to flush hit up Google for the finishing stages. – Graphus supports Monica Nov 22 '17 at 8:52
  • Also, 1500 is far too fine to sand to, as a rule there's absolutely no benefit to sanding wood that finely. Finish yes, bare wood no. If using a film finish (shellac, varnish or lacquer) sanding to 240 is the most you normally need to go, and stopping at 150 can even be sufficient. For an oil finish (no surface film) you do need to sand more finely, but around 600 is at the limit you'll see any improvement and 320 to 400 can be sufficient. – Graphus supports Monica Nov 22 '17 at 8:57

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