Hey Guys, rant time.
I just wanted to clear up the food grade argument, as no one has clearly addressed it.
First and foremost, yes, a lot of people are correct, there is NO DIFFERENCE between the food/medical grade gas and the commercial/welding grade gas. They come from the same source. The Airgas guy will tell you that thinking he's shattered Einstein's Theory of Relativity or something *cough* because he knows they are filled from the same valve.
HOWEVER there is a major difference. The packaging. Commercial CO2 comes in a straight up steel tank which will rust and taint the CO2, first of all being dangerous for your health, and second of all potentially flavoring your beer, as the steel will rust with any water exposure at all. (Before you get smart with CO2 protecting the metal, I can guarantee not all welders will be as careful with the tank before trading it in as you would be at home. Add in condensation on the valve from previous fills. Not to mention some of that .01% impurity is water and oxygen which by calculating the surface area of the tank, to volume of the tank uncompressed, it adds up. Also pressure is a catalyst for rust in steel.)
Medical/Food grade CO2 comes in a glass lined tank, which is washed between refills. It's not the CO2 that makes it food grade, it's the tank.
...This is along the same argument as fermenting in a $2 Home Depot bucket because it's #2 HPDE plastic. Sure, food grade plastic made in the same factory as the $20 brewer bucket, but the lube, and dyes are not food grade and will leach very toxic polymers into your food. Add alcohol, which is a solvent for many things that don't dissolve in water, and you've got a polymer extract going on. Ever wondered why Alcohol erases permanent markers, or in drinks like absinth, bring oils into solution that otherwise don't dissolve in water?
I'm always appalled at how quickly people disregard food safety. In a lot of ways you're no different from the Chinese products with mercury and lead. Won't kill you today, but it definitely isn't good for you. Sometimes your health is worth an extra buck. Additionally, not being educated isn't an excuse; especially if there's a blatantly categorized choice between food grade, and non-food grade.
