January 1, 2023
Woods, of course, feature varying properties and characteristics, and one wood property you should be mindful of is the hardness of the wood. Experts have already quantified the hardness of most wood species used for woodworking. Thus, you don’t need to do the actual testing to see how hard a wood species is. You only need to be familiar with the Janka Hardness Scale.
The grain’s direction often determines the density and hardness of wood. The most common way of figuring out wood’s hardness is by measuring the flat and horizontal grain of the wood. The vertical grain of the wood or the edge grain usually gets tested likewise. Yet, Janka Hardness Scale doesn’t show this result. The only result in the Janka Hardness Scale is the wood’s face hardness.
How Do They Rate the Hardness of Wood?
Long ago, wood’s hardness had yet to be standardized. However, in 1906, Gabriel Janka, an Austrian researcher, invented a scale named after him. This scale is called the Janka Hardness Scale. The Janka Hardness scale shows the hardness of various wood types relative to other wood types. The American Society for Testing and Materials (ASTM) standardized this scale in 1927.
The Janka Test is the method used for rating the hardness of wood. It measures the force needed to embed a steel ball about .444 inches thick into a wood plank by half the ball’s diameter. Thus, this test exhibits the wood’s ability to resist wear and dent. It indicates how hard a wood species is when sawn, milled, and nailed.
Wood species worldwide number around 10,000 or more. If you do the testing yourself, you might get confused. However, we now have the Janka Wood Chart or Hardness Scale because of the Janka Test.
The Janka Hardness Scale evolved from the Brinell Scale—a standardized hardness test designed for the fields of metallurgy and engineering. This test has been used since 1922 and was standardized in 1927, likewise.
Janka Wood Hardness Chart for Major Types of Wood Species
|Wood Types||Janka Rating (lbf)|
|Strand Woven Bamboo||4,000-5,000|
|Brazilian Walnut (Ipe)||3,680|
|Brazilain Teak or Cumaru||3,540|
|Black Palm Wood||2,020|
|Western Red Cedar||350|
Importance of the Janka Hardness Scale
The hardness of wood is a critical factor in the fields of construction and many other woodworking and carpentry industry. Thus, as a woodworker, knowing the Janka Hardness Scale can equip you with the proper knowledge about which wood you should choose for your woodworking projects.
The Janka Test gets done by embedding the steel ball measuring 0.444 halfway into the surface of the wood. The force needed to push the ball onto the wood is called pounds-force (lbf). This force shows how solid and dense a plank of wood is.
Thus, looking at the Janka Hardness Scale, you will notice that the Brazilian Walnut (Ipe) has a Janka rating of 3680 lbf. Hickory, on the other hand, has 1820 lbf Janka rating. So, it will take 3,680 pound-force to embed half the diameter of the steel ball onto Ipe wood, while it will take only 1,820 lbf to embed the steel ball onto Hickory wood.
Janka Hardness Scale: How Does It Work?
A visual assessment of the wood or an evaluation of its texture will not reveal outrightly whether the wood is hard or not. Thus, you need to know the standardized hardness scale of Janka. But how does Janka Hardness Scale work?
The Janka test gets done by measuring the force needed to embed half of the diameter of the steel ball into the wood surface. It’s like dropping a steel ball onto the wood and figuring out how much force it would take to bury the ball’s half its diameter into the wood. This test, of course, is done in a controlled laboratory environment.
One-by-one, every wood species gets tested, and the results get tabulated, resulting in the Janka Hardness Scale. The results, as mentioned above, are indicated in lbf or pound force, kilograms-force (kgf), Kilonewtons (kN), Newtons (N), or Janka. The lower the Janka rating, the less the hardness of the wood.
The Janka test is not designed to measure the scratch resistance of the wood, nor does it measure its resistance to scuffing or wear and tear. It only measures the ball’s impact on the wood, so it gets categorized as an impact test.
What Do the Janka Test Results Indicate?
As mentioned above, Janka Test is an impact test that measures the wood’s resistance against wear and tear and denting. It is a valuable test for determining how well wood will stack against constant usage and impacts. For example, when choosing wood for flooring, it will be best to choose wood species with a higher Janka Hardness rating. Remember that durable hardwood flooring is also timeless. Thus, with the help of the Janka Hardness scale, you can select the best wood species for your home flooring.
Hickory, for example, comes with 1,820 Janka, which is hard enough for hardwood flooring. You can also go for Maple with a Janka Hardness rating of 1,459 Janka or Ash with a 1,320 Janka. However, the higher the Janka rating of the wood, the more expensive it would be.
The Brazilian Walnut, for example, has a Janka Hardness rating of 3,800 Janka, which is relatively high. It is, therefore, an excellent option for flooring. Yet, it is very much expensive. Brazilian Cherry likewise has a Janka rating of 2350 Janka, which is also very hard. It is also costly.
Softwood and Hardwood Hardness
One common misconception about hardwoods and softwoods is that hardwoods are tagged as hardwoods because they are hard, while softwoods are soft. Yet, this is not always the case. One of the main factors when classifying hardwoods and softwoods is whether a tree sheds its leaves during autumn. This factor has nothing to do, of course, with hardness. Thus, it is right to say that hardwoods and softwoods are only biological distinctions.
Hardwoods, for example, shed their leaves during autumn, and they are all deciduous trees. They are also dicot species with seeds having two embryonic leaves.
Softwoods, on the other hand, come from coniferous trees, and they are all coniferous. They are angiosperms, meaning their seeds are not enclosed like those of pinecones. Of course, dicot trees feature a harder wood than the angiosperm wood species. Yet, you will also find softwoods with almost the same Janka Hardness ratings as some hardwood species.
What Are the Hardest Species of Wood?
As a beginner in woodworking, it will also help if you are familiar with the hardness ratings of the woods you will use for your primary woodworking projects. It will also help if you know the following hardest woods in the world:
1) Australian Buloke (5,060 lbf)
The Australian Buloke is considered the ironwood tree of the world. It is native to the Land in South (Australia) and can be found mostly in the Southern and Eastern Australia. It is considered the hardest wood worldwide with a Janka Hardness rating of 5,060 lbf.
2) Schinopsis Brasiliensis (4,800 lbf)
Schinopsis Brasiliensis is another very hardwood found in Brazil. It is a flowering plant species in the family of Cashew. Moreover, it is a tough wood with a Janka Hardness rating of 4,800 Janka. This wood gets frequently used in building and construction because of its incredible strength and hardness.
3) Quebracho (4,570 lbf)
The etymology of this wood’s name is from the Spanish expression “quebrar hacha,” which means axe breaker. Well, judging from its name, this wood might be very hard. It belongs to the Schinopsis genus and is very heavy and hard, with a Janka rating of 4,570 Janka.
4) Lignum Vitae (4,390 lbf)
Another tough wood is Lignum Vitae. Lignum Vitae, of course, is a Latin phrase that means “wood of life.” It is considered one of the world’s hardest woods and is listed as endangered.
5) Snakewood (3,800 lbf)
Snakewood is another wood species that is very hard and dense. It has a Janka Hardness rating of 3,800 Janka. It is a highly sought-after wood because of its unique markings and patterns, similar to snakeskin. It is, therefore, a costly wood.
6) Brazilian Olivewood (3,700 lbf)
The Brazilian Olivewood carries a Janka Hardness rating of 3,700 Janka. This wood is a beautiful exotic wood that combines hardness and durability with beauty. It is also a costly wood.
7) Brazilian Ebony (3,692 lbf)
The Brazilian Ebony is another very dense and hard wood with a Janka rating of 3,692 lbf. It is native to Argentina, Paraguay, and Brazil and is a perfect wood for decking and planking. It is shock-resistant, making it an excellent option for flooring.
8) African Pearwood (3,680 lbf)
The African Pearwood features a Janka rating of 3,680 lbf. It is mostly found in the Republic of Congo, Nigeria, Gabon, Angola, and Cameroon. It inhabits the lowland forests of the moist tropical region. This wood, of course, is also tough and durable.
9) Brazilian Walnut (3,684 lbf)
The Brazilian Walnut comes from South and Central America. It has a Janka Hardness of 3,684 lbf. It features interlocking to straight grains and is a very durable and dense wood. It is perfect for many woodworking projects.
10) African Blackwood (3,684 lbf)
You will find this wood in specific parts of the globe, an exotic wood that is highly sought-after. It has a Janka Hardness rating of 3,670 lbf. In the Dry Savanna Regions, you will find this wood primarily growing in Central and Southern Africa. Like all the wood mentioned above, it is difficult to work with using hand and machine tools because of its extreme hardness. It is also costly. Read More About African Blackwood.
The Janka Hardness Test is one of the best ways to determine the hardness of wood. It serves as a general guide for wood users to determine the estimated hardness of the woods they will use. It also comes in handy when comparing various wood species, you intend to use for flooring and other woodworking projects.
The Janka Hardness rating, of course, can help you determine how strong a wood species is against wear and tear. Nevertheless, when choosing wood for flooring, your two primary considerations should be its appearance and hardness. The balance between these two factors would be necessary to select the ideal wood for your projects.
Liam is a 37-year-old woodworker and interior designer who loves to make every furniture project an art piece. He is very experienced in furniture design and woodworking project planning.