What is the biggest cause of teak defects? Knots — scars where a branch grew into the trunk, bending the grain around them — now account for 44% of sawn-timber defects according to a 2025 non-destructive grading study. In workshop terms that means most "reject" material is not ruined wood, it just has a knot in the wrong spot. Reading that spot before the machine runs decides how much can be saved.
Buy a teak blank, start routing, then hit a knot in the middle of the carving area. Into the scrap pile it goes? In many workshops, yes. Yet the latest grading research says knots are the single largest defect — and they can be managed, not just discarded.
Our workshop faces this daily. Every teak board that hits the sorting table has its own grain story and its own knot positions. This article is about how we read them before the CNC starts.
Why knots are the main problem
Teak grows branches that, when they die or are pruned, leave a knot — the point where grain curls around the former branch. Strength and appearance change there. Towards More Accurate Grading: Non-Destructive Methods for Sawn Timber (2025, De Gruyter Brill) reports knots contribute 44% of all sawn-timber defects — the largest share by far, well ahead of checks, splits or warps.
That does not mean a knot is bad. In rustic furniture knots are desirable. But for precision work — like our calligraphy panels or wall clocks held to a tight 40 cm envelope — a knot under the cutter lifts the grain or causes tearout.
Non-destructive grading: read without destroying
The old way to spot defects was purely visual — an artisan eyed the board and guessed. The 2025 study pushes non-destructive methods instead: sensors that read density, grain direction and even moisture without cutting. Large mills already use micro-CT and microwave sensors.
For a small workshop that equipment is still expensive. But the principle is free: read first, cut later. We lay the board under a light, trace the grain, flag each knot. Then we adjust the design — sometimes shifting the toolpath 2 cm is enough to park the knot on an edge that carries no load.
Workshop trick: reposition, don't discard
This links to our earlier value-upgrading article. Material rejected for knots can often be rescued by placement alone. The CNC is precise — steer the path around the critical knot area and an off-grade board graduates to Grade A.
Sometimes we even use the knot as a feature. A calligraphy piece with a single knot tucked into the lower corner looks organic, not defective. It depends on the product and the buyer.
For buyers: don't fear knots
Buyers often ask, "what's this dark circle?" It's a sign of solid wood, not glue. Any solid-teak furniture will have a knot somewhere. The key is that it is not placed where it carries load.
If you spot a knot in our pieces, it means we chose not to waste a good board over a defect that can actually be managed — part of how we keep our prices accessible.
Like this kind of teak carving?
Browse our teak wood carved calligraphy collection. CNC-carved with ±0.1 mm precision, solid teak, hand-finished in Bandung.