This solve was made with one goal in mind: go from Very Hot Water to Suspiciously Stable Substance to Pepper Spray, all in three height.
Because 11 (atoms in Sus. Substance) and 9 (atoms in Pepper Spray) are relatively prime, the solve is coded out to 11 products, each one produced differently, the last of which is dropped on cycle 1329.
Arm 1 is an initialization arm, preserving the air and water from the first input so that the two elements can make it to the right half of the solve and serve as catalysts. These catalysts are then used as part of the 11th product and replaced at the beginning of the next loop. Since the next set of catalysts are duped off of the previous ones, only the first Sus. Substance is incomplete (minus the triplex bonds, of course)
Shoutouts to omclone, for without it I would not have been able to make this solve. 3577 instructions across 6 arms is not easy to program.
I programmed the left half first, turning the right half into an interesting Height/Cycles challenge that took me all week to conquer. (Technically, a true height/cycles solve would have the two halves closer together, but I stuck with this layout for the aesthetic of the line of Sus. Substance making their way across the field.)