The previous grease works well for most applications; however, some tasks involve more pressure than it can withstand. In these cases the lubricating film is broken, and failure occurs by welding or galling of the contacting surfaces. In commercial greases, this is resolved by complex additives which bind either physically (antiwear additives) or chemically (extreme pressure additives) to the metal surfaces; however, a simpler option is to add a mechanically resilient and lubricating filler, which takes up the impact when a heavy load is placed on the greased components. Historically, both white lead (basic lead carbonate) and black lead (graphite) were used for this purpose; however, due to the toxicity of white lead and the availability of graphite, I decided to use the latter in my experiments.
To make a grease based on this principle, I began by adding 12g of castor oil to a small beaker, to which I added 4g of carnauba wax and 4g of coarse (44µm) flake graphite. I then heated the mixture on a hot plate until the wax began to melt, then stirred it until it became homogeneous and removed it from the heat. After it had cooled to room temperature, I then removed the solid grease from the beaker and mulled it in the usual manner. The resulting grease was very thick, yet still slippery enough to be worked and manipulated without issue. As a qualitative test, I applied some to a dead center on my lathe, which I then used to support a long steel rod. The rod was able to turn smoothly despite significant pressure from the tailstock, so at this point I considered the grease a success, and packed the remainder into a paint tube for storage.
Since the previous grease was intended as a general-purpose lubricant, this new grease could be considered its heavy-duty counterpart. That said, this grease is fully adjustable, and intermediate consistencies can easily be achieved by varying the proportions of wax and graphite according to the desired purpose. As with the last grease, time will determine its stability, but so far it appears to be a suitable lubricant for high-load, low-speed applications.