All anti-spatters are not the same.
Typically, the good stuff is bad for your health, so is expensive, rarely available or used, and the bad stuff, which is really cheap, is used too much.
Any contaminate in a molten weld pool can affect the integrity of the weld.
Water based and other solutions can cause hydrogen to be absorbed in the weld and surrounding base metal, which in some cases leads to hydrogen embrittlement (micro cracking) and reduced weld fatigue life.
Welding through a puddle of spatter spray can also cause weld porosity.
Spatter sprays are useful for misting the areas surrounding the weld joint, and places where you know spatter will collect on the material. If the welder soaks the weld joint with it until he/she is welding through a puddle, they're doing it wrong. It really ticks me off when a welder says "I can't use spatter spray cause it gives me porosity." That's how you can tell when you've got a stupid one.
Tim
