What is The Janka Hardness Scale?

If you have spent any time perusing Matt’s Blog, or our guitar listings, you may have come across my articles about specific tonewoods like Alder, Ash, Spruce, Maple, Ebony, etc. A term that comes up in all those articles is Janka Scale or Janka Rating. In the simplest of terms, Janka = hardness. The Janka Test is a rating, or ranking system, for determining how hard different woods are.

Let’s stick to the facts to get the ball rolling

• Invented by Gabriel Janka, an Australian Wood Researcher in 1906, then standardized in 1927.
• The Janka Test is sort of the V.2 hardness test and is based on the Brinell Hardness Test.
• The actual test measures the force required to push a .444” steel ball into a piece of wood to a depth that equals half the ball's diameter.
• The Janka Hardness Number is measured in “pounds-force”. In other words and for example, it takes 3670 lbs of force to push a .444” diameter steel ball halfway into a piece of Blackwood. 

Guitar related woods and their Janka ratings

• Blackwood 3670
• Macassar Ebony 3250
• Gaboon Ebony 3220
• Cocobolo 2960
• Zirocote 2200
• Bubinga 1980
• Indian rosewood 1660
• Hard/Birdseye/Curly Hard Maple 1450
• Sapele 1410
• Swamp Ash 1320 (varies greatly!)
• South American Mahogany 1200
• Soft/Curly Soft Maple 950
• African Mahogany 830
• Alder 590
• Poplar 540
• Sitka Spruce 510
• Redwood 420
• Basswood 410
• Sugar/White Pine 380

Many desirable Ebony Species come in above 3000 on the Janka Scale while Basswood comes in at just 410. Considered the hardest wood by many is Australian Buloke (or Bull Oak), whose rating varies from 3700 to 5000. The softest wood is Balsa coming in at just 70. 

Something to consider is that every piece of wood would/could/should have its own Janka Hardness Rating, the ratings shown above are ‘average’ if you will. Lumber is not perfectly uniform in regards to density and almost always has softer and/or harder spots. To make things a little more confusing, hardness can vary with the direction of the wood grain.

Overall, the Janka system is fairly simple, easy to understand, and certainly helped me put the build process into perspective. It is NOT 100% accurate and is more for getting a baseline understanding of comparative hardness rather than an unflinching number that is 100% accurate, 100% of the time.

From Journalistic to Editorial, here come the opinions!

People ask, “Is this a good Janka rating?” and that question can not be answered without asking “For what?”  One must ‘situationalize’  the usage of a material before we can determine if it will excel in the usage. The species that make a great fingerboard make the WORST acoustic guitar top. The Wright Brothers didn’t use ebony when they built The Flyer, they used Spruce and Ash for their strength to weight ratios. From my 30+ years of playing and 15 years of building my own electric guitars, I believe that one must balance the hard and softwoods in a build to get the best possible guitar. Since best is subjective, one must come to their own conclusion about how hard and softwoods blend to make a killer guitar.

Acoustic and Electric guitars will have a mixture of soft and hardwoods but an Acoustic REQUIRES a softer wood top for the guitar to sound good. The top must be able to flex and bend to push sound. Think about how a speaker vibrates when you play music through it. That’s essentially what we want the top of an acoustic guitar to do. This is why Spruce and Cedar are most often used and considered the best wood for tops. Mahogany and Sapele are also used, but due to their considerably higher Janka rating, they typically sound darker, warmer, and quieter than a comparable model with a Spruce top. Save those heavy, oily, dense woods for the back, sides, neck, and fingerboard!

For me (and many manufacturers), I prefer a softer wood for the body of an electric guitar, something under a rating of 600. They (the good ones, anyway) absorb the resonance of the strings and feed it directly into my ribcage. I thoroughly enjoy ‘feeling’ my playing in my bones, it doesn’t get any more inspiring for me! My favorite guitar has a one piece, figured port Orford cedar body and a 1 piece, comparatively soft but shockingly stable piece of Maple. Fewer pieces of wood mean less glue and a very "Pure" guitar. 

A neck should be made from harder, denser, and more stable wood than the species selected for the body but NOT harder than the fingerboard material. Maple and Mahogany are the two most often chosen woods for neck material as far as manufacturers are concerned. With Maple ranging from 950-1450 and Mahogany from 830-1200, both materials come in with a higher rating than all of the typical Electric Guitar Body Woods (save for Swamp Ash which unsurprisingly produces a very bright sounding guitar). Going with a VERY high rating for neck material all but guarantees you’ll have a neck heavy guitar that likes to dive towards the floor whenever you take your left hand off of the neck. Save those woods coming in over 2k for your fingerboard!

Fingerboard Materials are typically selected from woods ranked above 1400 on the Janka Scale. With Hard Maple coming in at 1450, Indian rosewood coming in at 1620, and (many) Ebony species coming in over 3000. Within the 3 most common fingerboard materials, we experience 3 distinctly different performances/influences from these tonewoods. Depending on what your goal is for a guitar, a recommendation could easily shift to another. 

• Maple: a strong plosive with the most powerful initial attack. Bright, articulate, and very lively. Least impressive for warmth and sustain.
• Rosewood: smooths out the plosive/initial attack. Heavier, denser, darker, and richer in tone than Maple.
• Ebony: very smooth, less ‘peaky’ than maple but brighter than rosewood. Heavier and denser than both. Many find Ebony to be a superior fingerboard material.

I have a healthy interest (not an obsession ok, OK?!) in timbers and have used what most players consider alternative woods in my builds. My choices seem strange to some, but I consult the Janka Scale before adding a slab to my wood pile to get an idea of where it will sit, tone-wise. To my ears, the hardness of wood determines its tonal properties far more than any other property of that wood.

Thanks again for visiting Matt's Blog, and sorry for the less visually interesting post this time around, but there is not much to show off during this conversation! There is more to discuss than look at when it comes to the Janka Scale. It truly is a critical (and fascinating, to me at least) thing to understand if you are into attempting to deconstruct the DNA of a guitar.

This Blog Post was penned by Mathew Janka-ins.