As you will find out there are a lot of terms connected with wood, especially tonewood, such as grading, tone, tap tone, color, grain pattern and run-out, just to name a few.
Top tonewood and back tonewood are graded for different characteristics that are inherent in a certain species of wood. For instance:
How To Find Great Tonewood:
Fine Grain: (The annual rings number a minimum of 20 per inch)
Consistent Color: This means that across the entire surface of the top, the coloring remains the same. No streaking, and no imperfections.
Minimal Runout: Runout is an indication of how the wood was sawn from the log (See Luthier Glossary) Absolutely no run-out is preferred.
Stiff – Not Rubbery: When the top tonewood is flexed there should be lot of resistance from flexing and not feel like it is a piece of cardboard.
Silk: This is the cross-grain of a piece of wood. (See Luthier Glossary). It is an indication that the top was cut nearly perpendicular to the annual rings and this is a sign of an excellent top.
Vertical Grain: When looking at the edge of the wood the grain should run nearly vertical along the width of the piece. An excepted standard is that it should not exceed 20 degrees from vertical at any point.
When purchasing from tonewood supplier sites or visiting an instrument wood lumber yard. You will note that there are basically (4) grades of wood:
- Grade A: This is just OK wood it would typically be used on lower quality instruments or lower priced factory guitars. Typically in a grade A top expect to see some run-out, inconsistent grain pattern, color streaking in the top and grain that exceeds the 20 degree from vertical standard (more like 45 degrees at worst). The tops could also be quite flexible with grain not meeting the 20 grains/inch standard. Usually top of Grade A have some sort of imperfection that prevents them from making it to Grade AA. Use this top on guitar approaching $700.00.
- Grade AA: This is standard grade and is the grade that most factory guitar are using. It is very plentiful and could be used as your starter guitar. The top will be structurally acceptable for stiffness, vertical grain, and run-out, but will fall a bit short in the color, tight and consistent grain catagories. Quite often you can get such good tops in the AA catagory it is viturally impossible to distinguish them from a grade AAA.
- Grade AAA: Top grade top. Even color, stiff and find, consistent grain pattern. Nearly vertical grain with absolutely no imperfections. You would use this on some very fine instruments.
- Master Grade: This is truly an almost perfect top in every way. It has all the characteristics of the AAA tops plus it has moderate to strong medularies (silk pattern). This is truly a one in a thousand guitar top and should be reserved for all but the finest instruments.