u/SeaworthinessDry5334

Pulled this from a residential removal — the live edge (the natural bark-line edge, uncut) runs the full length and that's really the whole story before resin even comes into it. Most live edge pieces people see in resin work are dining-table scale; this is smaller but the same principle applies — the tree's actual outline becomes the design instead of something you cut away to get a straight board.

What's interesting from a pour perspective: the bark-line edge is exactly where moisture tends to sit differently to the rest of the slab. I checked MC at the centre, the edge near the bark line, and about halfway between — three separate readings, not just one centre spot. Came in at 9% across all three this time, but I've had pieces where the zone right under the bark read 2-3% higher than centre because that area dries slower.

If you're keeping the live edge intact (rather than squaring it off) for a resin pour, that's the zone worth double-checking before you commit — a single centre reading can look fine while the bark-line zone is still releasing moisture.

Burl grain doesn't behave like straight grain in resin work and it's worth understanding why before you pour.

In straight-grained timber, moisture content is relatively even across the face. In burl, the interlocked grain creates pockets — the dense knot clusters hold moisture longer than the surrounding wood. I've measured 2-3% MC differential between the centre of a burl formation and the edge of the same slab.

That matters because resin cures against a moisture gradient. Pour over burl at 12% average MC and you might have pockets sitting at 14-15% — enough to cause clouding or adhesion failure at those points even when the rest of the pour looks clean.

This piece is plum burl recovered from Sunnyridge, Germiston. Milled January 2026. MC measured at 8% across the full face before listing — including the dense knot clusters at the centre.

That's the reading you want before a resin pour on burl.

Every so often someone asks why a round that's been air-drying for a year still opens up new cracks once it's brought inside or close to sealing. The short version: the outside drying fast and the core drying slow is the whole problem, and it gets worse the bigger and rounder the cross-section is.

This one's a root flare slab pulled from a stump in Edenvale, Gauteng — milled 2026-02-03. First pin-meter reading on 2026-03-01, taken at several points across the face rather than one spot, came back 10-12%. That's roughly a month in and it's still field seasoning now, stacked indoors with stickers through a Highveld winter. Slow and steady, but worth the wait — it ends up more stable long-term than forcing it through a fast kiln cycle.

The radial cracks running out from the centre are the wood relieving that uneven moisture loss between the outer rings and the core. Root sections do this more than straight-grained boards because the grain itself isn't running in one direction — it's radiating out from where the roots forked. The crack pattern is basically a record of where that stress let go first.

For resin pours these aren't a flaw to disguise — a clear or lightly tinted epoxy fill follows the crack the full depth and gives you a line through the grain that filler can't replicate. Just confirm MC before you pour. Surface-dry and core-dry are two different things, and a slab this size can fool you on that for a long time.

Working with ground stump root sections from urban salvage, the void structure is usually the whole point — crescent-shaped hollow centres, borer beetle channels, bark inclusions from where the root split around an obstacle. These aren't defects. They're the identity of the piece.

But voids require different prep depending on what you're building.

If you're filling with resin

Seal the void walls first with a thin coat of CA glue (cyanoacrylate) and let it cure fully before any resin touches the wood. Unsealed voids are thirsty — they'll absorb the first pour unevenly, creating bubbles and weak spots in the fill. CA wicks into the wood fibres, stabilises the edges, and gives the resin a consistent surface to bond against.

For borer beetle channels specifically — the tunnels are often narrower than they look on the surface. Use a dental pick or thin wire to check depth before sealing. Channels that run deeper than the cut face willtrap air during a pour and push it out as bubbles hours later.

If you're leaving voids open Shellac or a thin oil finish works well for natural edge pieces and display work. It seals without encasing. The void stays visible and tactile. Let it fully cure before any handling — uncured finish in a deep channel takes longer than you expect.

When to think twice about filling at all

Ground stump root sections in particular — the void geometry is part of what they are. A crescent hollow that runs through the full thickness of a cookie slice can be more interesting left open than filled. The surrounding wood tells the story. Resin can complete it, but it doesn't always need to.

The pieces that don't need filling: display pieces, wall art, specimens that aren't going to take contact or weight. Field seasoned urban salvaged timber that's documented and stable isn't going to move on you — you can leave structural decisions open longer than you think.

What void geometry are you working with?
Borer channels behaved differently to bark inclusions and natural checks — happy to go into the specifics if it helps.

Most salvaged wood fails resin pours for one reason — nobody checked the moisture content before casting.

This piece came from a ground stump removal in Edenvale, Gauteng in February 2026. The stump had been dead for over 7 years before I pulled it. The hollow in the centre wasn't cut — nature carved it. Root decay over years created the void structure you're seeing.

By the time I got to it, it had been drying in the ground for the better part of a decade. I still put a pin meter on a sanded face before listing it. Reading came back at 10–12%. That's the number that matters. Below 12% and you're in safe territory for deep pour epoxy. Above it and you're trapping moisture — bubbles, delamination, the pour fighting the wood from the inside.

The MC reading is documented. The harvest location is documented. The stump age is documented.

That's what "can you trust it" actually means. Not the species, not how it looks — the moisture number, taken on a sanded face, before it ships.

If your river table cupped, cracked, or delaminated after the pour, the wood is almost always the cause — not the resin.

Here's what's actually happening in each case.

Cupping after the pour

Cupping means the wood is still losing moisture unevenly. The surface dried faster than the core, so the core is still shrinking while the surface is locked in place by the resin.

The wood wins. It always does. The fix isn't a better resin — it's drier wood before you pour.

Cracking post-cure

If cracks appear days or weeks after the pour, the wood was still moving when you encapsulated it. Resin doesn't stop wood movement — it just makes it visible as a crack instead of a warp. Wood needs to reach equilibrium with its environment before any pour touches it.

Bubbling and adhesion failure

Wood above 12% moisture content off-gasses during the exothermic cure reaction. Those bubbles aren't air pockets from bad mixing — they're moisture escaping from wood that wasn't ready. Field seasoned timber that's been allowed to dry slowly over months behaves completely differently to timber that's been rushed.

The pin meter mistake everyone makes

One reading in the centre of the slab is not enough. Moisture content varies significantly across a piece — edge to centre, face to end grain, top to bottom. A slab that reads 10% in one spot can read 18% three inches away. Take readings at six to eight points minimum and average them. If any single reading is above 12% — the wood isn't ready.

Target before any pour: 8–10% MC

That's the range where wood is stable enough to encapsulate. Kiln dried lumber from a supplier hits this range but can climb again in storage. Urban salvaged timber that's been field seasoned properly — outdoors under cover, stickered flat, for six to twelve months minimum — will reach this range naturally and hold it.

Ground stump root timber and burl sections take longer than straight-grained slabs. The density and irregular grain mean moisture escapes more slowly. Budget extra seasoning time for anything with significant figure or void structure.

The pour didn't fail. The prep did.

Been milling and seasoning plum burl and ground stump root sections

from urban tree removals in Gauteng. One thing that comes up constantly

when people ask about wood for resin: moisture content matters more than

most listings tell you.

Wood that reads above 12% MC will off-gas during a pour. You get

bubbling, adhesion failure, and sometimes full delamination weeks later.

The problem with most online wood sellers is they don't measure or

disclose MC at all — you're buying on assumption.

What I do before anything goes into a pour:

- Measure MC with a pin meter at multiple points across the face

- Field season outdoors first, then move indoors for at least 30 days

- Re-measure before listing — target is 8-10% for our pieces

The borer beetle galleries in plum burl are actually a plus for resin

work — the channels fill completely and create surface patterns you

can't replicate artificially. But only if the wood is properly dry first.

Anyone else measuring MC before pouring? What threshold do you work to?