Humankind has been pondering the age-old question of whether shampoo or conditioner is the superior grooming agent since the dawn of time—or at least since Adam Sandler made them eternal rivals that were fighting for dominance of his scalp in Billy Madison.
Despite having common enemies in sweat, sebum and static electricity, shampoo and conditioner actually contain opposing ingredients. Shampoos usually have negatively charged ingredients, such as sodium lauryl sulfate (which is found in most cleaning products that produce a lather). Conditioners, on the other hand, typically contain positively charged ingredients, like cationics, which work to neutralize those negative charges in shampoo that create flyaways. “Due to their opposite charges, these two groups of chemicals react when combined, in effect ruining their original functionalities,” says cosmetic chemist Mort Westman. (No word yet on the role that “borophyll” plays in the reaction.)
To create a two-in-one that works better than squirting both shampoo and conditioner on your head at the same time, chemists develop formulas that play nice together, allowing you to clean and condition your hair simultaneously. Their trick? Creating a precise blend of ingredients. “They help keep the shampoo and conditioner from canceling each other out,” explains chemist John Malin. Without the perfectly blended mix, the shampoo would wash the conditioner out before it’s absorbed, or the conditioner would weaken the shampoo before the shampoo has a chance to clean.
So while we generally support taking matters into your own hands, it appears that in the case of two-in-one shampoo + conditioner, buying one off-the-shelf is the best solution. Save your DIY time for something more useful, like your personal drone project.