Comet is bleach (technically cyanuric acid, which is a component of bleach), and BKF is oxalic acid, which is primarily used for removing rust and other stains on metals. Short version: Comet is good for scrubbing and bleaching, and BKF is good for stubborn stuff on metal and non-porous surfaces.
I’m not a chemist; I was trying to break it down into the basic differences between the two. I apologize that I didn’t get the chemical name correct based on the information I was using from the MSDS and allowing myself to be influenced by the marketing that put “with bleach” on the front of the Comet can and didn’t research more thoroughly.
I’ve seen things about Coke (as in Coca-Cola) working wonders on rust in tubs
Coke contains (some) phosphoric acid, but also a bunch of sugar and caramel coloring, so it’s not the most effective thing. The active ingredient in BKF is oxalic acid, which works more directly and without the extra stuff.
Every time I get an ask involving a stain where my answer is “rubbing alcohol” (ballpoint pen, hair dye, etc.), someone always pipes in that you should use hairspray instead. Here’s the thing: hairspray works on stains because of the alcohol content in it. However, it also has a lot of added ingredients, like the polymers or gums that make it sticky, and fragrance, and sometimes silicone for shine and water-resistance. Those added ingredients can leave behind their own residues, and can interfere with stain lifting.
So, pick up a bottle of rubbing alcohol. It’s a buck or two. Comes in handy.
Makes total sense to me!
An alcohol and a carboxylic acid (like acetic acid) when mixed form an ester, but you have to heat it and use another (stronger) acid as a catalyst. Esters are often known for smelling nice (although not always)!
Smart people everywhere!
I went to the experts for this one, because all I could tell you is that alcohol gets up stains and residues, but it’s really drying; and vinegar is acidic, so it dissolves stuff.
Fortunately, my friend @themoderatelyambitiousscientist is smarter than I am, and offers this explanation:
Basically, rubbing alcohol is good at dissolving non-polar compounds, like oils. Acetic acid [vinegar] is good at dissolving both non-polar compounds and polar compounds (salts and sugars). So acetic acid is better both because it doesn’t evaporate as fast and also because it can dissolve more stains. But some cleaners use both together.