The other ingredients listed are important to how oxiclean works as well. If you google them you'll see that one is a surfactant (ethoxylated alcohol) that breaks the surface tension of the water to allow the cleaner to reach all of the crevices and the other (sodium polycarboxylate) is basically to help keep dirt and minerals from re-depositing on the item being cleaned-basically a phosphate replacement if I understand it correctly. The 1% sodium metasilicate is an alkaline cleaning agent.
PBW is 30% sodium metasilicate (a lot more than oxiclean), Sodium percarbonate, phosphates-possibly TSP (banned in a lot of household cleaners here in the US), a chelator (possibly ETDA), and a surfactant. I think the phosphates and chelator are what helps the cleaner to work so well with hard water. If you don't have hard water the phosphates and chelator may not be as necessary. I have hard water and even oxiclean leaves deposits if I don't rinse immediately. Cleaners with phosphates work really well for me. You could do something like 56% sodium percarbonate, 30% sodium metasilicate, 10% TSP (the real stuff-phosphates), 2% surfactant (?- not sure what), 2% EDTA. It's just a guess and you could probably leave out the EDTA and find a replacement for the phosphates but I think you'll want a surfactant of some kind in there.
I hope this helps some. My understanding of this is pretty superficial.
I just bought some PBW for the first time in a long time and it works better than anything else I've tried.
