for something with a fine edge you want roughly 0.7-1.3% c30 or c60. usually you want the harder one on the side of contact and the softer on the spine as a point of flexion; differential tempering just draws these high-carbon elements (literally diamond in c60s case) to the nearest temperature geodesic. the rest of the mixture of copper, iron, chromium, and tin is predominantly used to homogenize the configuration the matrix will shift into during tempering.

c30 and c60 are what is left behind from burning wood and then separating the ashes. or, pot ash; the heavier c30 (which bonds in large water-permeable chains) will sink and the lighter more buoyant c60 (owing to its arrangement) will float on top, evaporation separating them naturally. Their counter-intuitive mass to buoyancy ratio applies even in atmosphere, so simple weight calculations don't work exactly. It will always be a few g/cm2 off from true, even after the lengthy evaporation processing to try and homogenize their weights and positions. This is one of the properties that makes them useful in metallurgy for complicated reasons.

flux is used the same as in soldering, as a replacement process to guide elements into different temperature ranges in the matrix arrange. often each individual metal finds itself paired with a specific flux that burns off, and much of the waste of modern metallurgy revolves around having to use these intermediaries and the effect they have on matrix formation even if they are fully consumed by the reaction or precipitated as a post-reaction catalyst to be separated and recycled. The space it took up during melding interferes with matrix generation, the same as throwing raw wood in.

different applications require different mixtures, but for a simple burned wood infusion without separation or clarification you could probably make some kind of heating vessel. like a pot.

it's usually done by weight, I think volume varies by the tree significantly. I believe dutch aspens are closer to 5.5% by volume for instance.

3.4% by weight is closer to oak or other hardwoods, although hardwood is such a wide classification that you see 0.9-11% by weight requirements to get the same c30 and c60 carbon arrangements out and into the matrix.

cast iron results from too much of the tree's oils becoming the flux medium, and thus isn't fully reacted. so if it gets too hot these crystallized iron tree saps will ignite basically, ripping the matrix apart.