I'm new to this topic. What would be a simple explanation of wood grain? When you look at a wooden table or wooden panel, how can you describe it in terms of what you see?
To the eye, wood grain is a change in color or evenness of the surface. It may take the form of
- subtle shading across a piece
- wide or narrow stripes running along or across
- darker or lighter colors around a blemish (such as a knot) in the wood
- strong figures, such as chevrons or swirls of a contrasting color
- small pits (open grain) running in broken lines along a piece
There is a huge variability, both within and across species. There is even variability within a given piece of wood depending on the section, and depending on the angle on which it was sawn.
Grain also is used to refer to the relative strength of wood, and its holding power.
What grain means depends on what you are trying to determine.
At its most basic, wood grain is the variable density of the concentric growth rings caused by seasonal changes, moisture availability and growth environment. For decorative purposes, wood burl, bird's eye, ray fleck, color variation between heartwood/sapwood and other growth oddities also enter into the equation.
How it affects wood use and finish depends on how the raw product is processed (veneer, quarter sawn, plain sawn, turned) to create finish product.
Depending on the species, the grain orientation after processing can affect strength, warpage, dimensional stability, retention of squareness (diamonds or trapezoids as it loses moisture) and in cases of hillside growth and fast growth, compression wood can render the finished product nearly unusable.
As described in Wikipedia, "grain is a "...confusingly versatile term..." including the direction of the wood cells (straight grain, spiral grain), surface appearance or figure, growth-ring placement (vertical grain), plane of the cut (end grain, quarter sawn, flat sawn, etc), rate of growth (narrow grain), relative cell size (open grain), and other meanings"