For example, my formulations #8 and #9 are very similar. Their main ingredient is the same. Their third ingredient is the same. All the ingredients have the same relative proportions. The only difference is the secondary ingredient is different, though on paper they should perform about the same.
This morning I finally got around to trying SS#9, the fraternal twin formulation to SS#8. It only took one pass to be certain that SS#9 was a dead end, and the lineage of SS#8 and SS#10 was the direction to continue to pursue. The lather of SS#8 and #10 is much more lasting, creamy, moisturizing, and slick.
So the test puck of #9 goes into the refrigerated archive, while tweaks and testing continues on the best formulations.
What are your favorite shave soaps and why?