The Bloodroot Blades shop and office in Arnoldsville, GA. 

Identifying and selecting good raw materials is a significant component of our process. Here we are looking at an unusual, highly-burled red maple tree that will yield several years’ supply of spalted maple burl. 

Here, we are ripping spalted pecan logs down to the size a bandsaw can handle. The chainsaw often gives us the best early hints of the future grain and coloration of a piece. 

Then, we cut wood into handle-sized blocks for further drying

In the loft of the shop, we have racks of wood cut into handle blocks and in various drying stages. Once they are very well air dried (which takes many months or even years) we use a drying cabinet (that we built) to prepare them for stabilization.  We test the blocks with a moisture meter and usually take them to around 5-7% before mailing them to K&G for the best stabilization service in the country. 

We select our steel from many different sources. Depending on the source (granite cutting, log cutting, files, car parts) we often guess at alloys according to what an engineer from that source would likely have chosen. We further refine our guess by spark testing the metal on a grinder to get a very rough idea of carbon and alloy content. If our initial testing looks promising, we forge it and do a basic heat treat - quenching in oils of thinner and thinner viscosities and finally brine, each time breaking and hardness testing to get an idea of hardenability and potential. If strength, visual grain, and hardness check out, then we send the steel to a metallurgical lab for a full analytical breakdown. Here David is cutting strips out of a custom smelt 1080+ 0.6 chrome German-built granite cutting sawblade we got from Elberton, GA.  

We enjoy forging by hand.  It is very physical, but it also slows us down and forces us to commit to the process for several hours at a time.  Between hammering sessions and while we put the metal back in the forge to heat up again, we have good discussions about the business, life, etc. We typically keep 2-4 pieces of steel in the forge so that we have a constant rhythm.  More and pieces over heat, fewer and we're doing more talking than forging. Many knifemakers do not forge, and you don't have to to make a great knife. But we love watching as our right brains shape a piece of steel into something useful. Forging also expands the variety of sizes and shapes of steel that we can use. 

For our full-tang knives, we have to drill holes in the tangs to attach handle scales. In order to do this, the steel has to be soft enough to drill. We prefer a form of spheroidal anneal - heating to just under critical (around 1200 degrees or so) in an extinguished forge, and then we let the knife slow cool. This is not a true spheroidal anneal and not a lamellar anneal, but it works very well and much better than a lamellar anneal for most alloys we use. It gets the blades plenty soft.  In our shop, we anneal the handles, but unlike many makers, we do not typically anneal the blades. Instead, we forge close to the final shape, and we only grind after heat treatment. 

Here we double and triple check our customer's order and plan what we need to continue to grind off our current shape in order to dial in the requested profile.

Finally, we get to the step where we match the blade and handle shape to the image we have in mind. This part of the process is very rewarding because before this step, the minor lumps along the edge from forging and the rounded tip and heel only suggest what the final product will be. Once we clean up those edges and abnormalities, the character of the final piece begins to show itself. 

We mark the location of the handle pins and drill them out on a drill press. Beware of the piece getting bound up and rotating with the bit. We typically clamp the piece to the table, or like in the picture, plan for its accidental rotation - here, it would stop on the bar, only rotating a quarter turn and away from our hands. 

Our maker's mark is very simple and is slightly different every time we do it, which we like. We use a single B stamp and stamp twice to get them back to back. The variation and simplicity gives clear evidence that our pieces are handmade without affecting the quality or functionality of the knife. 

After forging and annealing tangs, the molecular structure of the steel is uneven and alloy elements may be bunched or unevenly distributed. Normalizing wipes the slate clean and resets the steel to an even grain size and evenly distributes alloying elements. This step is critical; it sets the stage for all other heat treatment procedures. In the practice of normalizing, we heat the steel to a suggested temperature for the alloy, hold it for a little while to let the carbon and alloying elements distribute, and then let the piece air cool.

During thermal cycling we are heating and cooling the blades rapidly in descending heats. As it heats and cools, every time the steel crosses  the transformation threshold of austenite formation, it nucleates new grains (crystals) in the boundaries of the old grains. This shrinks the grain size of the steel, which improves the durability and edge stability of the finished blades. Some steels are inherently fine grained and need this less than steels that are not and there is no magic number of cycles. One has to be careful here, though:  too much cycling or too low a temperature can ruin our work during the initial normalizing step by clumping the alloying elements that we had just redistributed.

As a solid, steel has an impressive variety of molecular structures, and during the stages of production we have been discussing, we take it through many of these possible structures. But, to give a knife its soul, we must finally transform the steel from the many states it has been in into martensite, the structure of hardened steel. To form this structure, the steel must first be austenite which occurs at a high temperature. Alloying elements move at different temperatures and diffuse into the steel over time, so the temperature at which steel transforms into its austenite form varies.  To get the best performance out of each type of steel, each steel requires different types of heat control and requires one to hold the steel at temperature for differing lengths of time. Knowing each steel's requirements to achieve austenite and then martensite is essential in getting the best performance out of each steel, and, then, each knife.  To meet the needs of each of our steels, we use electric kilns, salt pots, and the forge depending on the alloy and its specific requirements or tendencies. Decarburization and heat evenness are also essential considerations during this stage. 

This is the place where we force the steel to become martensite. To do this, we must rapidly cool the steel through specific temperature ranges. The rate of cooling to force the steel into martensite, however, varies among alloys. Some of our steels need to cool 600 degrees in under 0.6 seconds. To vary the rate of cooling, we use different quenchants. Brine is the fastest and harshest quenchant and distortion, warping, and cracking are real risks when we use it. Unfortunately, though, the shallowest hardening steels require brine. Thankfully, specially designed quench oils meet the requirements of most of the alloys we use. Canola oil works all right for a medium speed oil, though it is messy. In this picture, we are using Parks 50, one of the fastest cooling quench oils on the market and one of our main quenchants. After this step, the blades air cool to room temperature and then are immediately "snap tempered" for two hours at 300 degrees F to relieve internal stress.  After this, most steels have become martensite.

For some alloys, quenching to room temperature alone does not allow for full transformation of the steel to the desirable martensite. Many of these alloys also have carbide forming alloying elements. Cooling the blades in liquid nitrogen both ages and transforms the carbides and pushes all of the remaining austenite to form martensite. This is not necessary by industry's standards for most of the steels we use, but for some it helps push performance to a higher level. 

Once the knives slowly return to room temperature, they are placed back in the oven around 300 degrees for a few hours. 

Tempering allows some good windows of time for other activities. . .

We test hardened steels for their degree of hardness on the Rockwell C scale (often denoted as HRC or Rc).  This machine uses a system of weights and levers to apply a 150kg weight onto a 120 degree diamond-tipped cone, which is placed against the knife blade. The depth to which the indenter penetrates records the hardness of the steel on the guage within 1 HRC point of accuracy. We take several measurements and average them to make sure we are getting true readings. 

Once the knives have been tempered to their target hardness, the spines and tangs of the knives are softened with an acetylene torch to increase shock resistance and durability and allow any straightening that we need to do at this point or later in the process. 

In this step we relieve the stress in the steel from the quenching process and take the blade's toughness to where it should be for the design and intended use of that particular knife. After an initial snap temper we grind and polish an area of the blade for Rockwell hardness testing. If the quench was successful and the blade is fully hardened to the alloy's maximum hardness, we take the blades through several two hour cycles of increasing temperature until they reach the target hardness we are looking for. 

Here, we transform the blade into its final shape and geometry.  We finally get to make the knife into a piece that will cut efficiently, flex appropriately, release food, and really perform. Grinding and Polishing is one of the most exacting and time-consuming steps in the process.  

Once we take the blade to its final dimensions, we can test its heat treatment and the quality of the grind. This is a qualitative test and experience with different heat treatments and steels comes into play while we observe the strength (resistance to deformation) by feel and resilience (it should spring back completely without bending or breaking). This test can also identify decarburized or de-tempered areas if they exist on the blade. 

Similar to the edge flex test, blade flexing helps identify potential problems in heat treatment or geometry. The blade should flex and return to completely straight. The amount and location of the flexibility on the blade can be very important for the functionality of the knife. This test can also identify any invisible cracks in the blade that might otherwise only be discovered months or years down the road by the customer when a knife breaks under stress. 

In order to be confident in heat treatment and the performance of specific alloys, full destructive tests must be done. To find the best balance of toughness and strength for an alloy, we must know what it takes to make a blade fail.  Tip breaking and dropping the knife from head-height tip-first into brick and then cement gives us multiple opportunities to test the most vulnerable part of the blade and see if the tip bends, breaks, or deforms and to what degree. In professional use, kitchen knives are often "tipped" when dropped onto tile and recreating these stresses is helpful in understanding a steel's weaknesses. 

Breaking tips or blades is necessary to get a view of the internal structure of the steel. If an alloy has been overheated or improperly cycled, it will show coarse grain, which often causes brittleness. We check to see if the surface of the broken steel looks like broken fine ceramic - a smooth matte surface with indestinguishable grain clusters. 

Here we get to play with the texture, color, and character of the handle to design a knife that is pleasing to the eye. This often takes a lot of time and conversation as we select the design that will flatter each knife.

Jeweler's files and patience are key ingredients at this stage as we make sure all joints are tight and cleanly fitted.

Once everything is dry fitted, we clean all surfaces with acetone for good glue adhesion and then we glue up. We primarily use G-Flex epoxy which has shock resistance and excellent toughness, something that is rare in epoxies. If we have to take a handle off to put a different one on, we literally have to crush the handle with sledgehammer and anvil and even then the G-flex must be removed from the metal tang by grinding. This epoxy is stronger than the wood or other materials. Remarkable stuff.

After the glue sets overnight, we shape the handles on the grinder and prepare them for hand sanding.

Here, we remove coarser scratches and refine the finish. We often sit on the shop bench outside and work together so we can talk while we sand.

We finish our handles with 0000 steel wool for a fine, smooth, but not too glossy finish. 

For the finish, we use Danish oil, waxes, or cyanoacralates, depending on the handle material.  Putting on the finishes shows the handle materials in their full beauty for the first time, and the process always feel like a ceremony. We never know for sure what the grain or pattern will look like until the very end.  We drop whatever we are doing to observe this step.

We believe the best edges are made with Japanese waterstones. Sharpening is a never ending rabbit hole and we do many different types depending on the style of knife, but a good standby is a coarse diamond plate for setting the initial bevels, 1200, 4000, 6000, debur on wood or cork, strop on wood-backed leather with chrome oxide a few times, or newspaper until all the burr is gone and we have a polished edge, then two light strokes on the 6000 to give the edge some aggressiveness. 

Now the knife is ready for use. An essential part of our knifemaking process is sending out pieces to kitchen professionals and knife nuts for feedback and testing. There is always more to learn and listening is perhaps the most important skill for us in this craft. 

Thank you for walking with us through this process.  It is a doozy, but one that we love.