Caramel: Stirring?

I feel that this is a case where multiple methods can be used to achieve the same result. I actually don't stir in the beginning since I first put the water in the pan THEN add the sugar by pouring it into the center of the pan onto the water, which keeps stray crystals from getting wet and clinging to the sides of the pan during stirring. When heated gently, the sugar dissolves slowly and hydrates fully while coming up to temperature without crystallizing. Perhaps I am one of few, but I have never had a problem with crystallization using a covered pan in the first stage of cooking, and, as it actually keeps water from reducing at first, it can prevent problems from accidentally cooking at too high a heat at which point the water can reduce more quickly than desired causing the sugar to burn. Since in many cases you would either be washing down the sides of the pan or keeping a lid on while the initial amount of water is still present, you are much less likely to have a problem than you would if you were adding water to the sugar after evaporation (at which point, the hygroscopic nature of sugar could cause it to crystallize). Condensation does, however, cause the crystallization of cooled confections and caramel which is often why the shelf life of such products is shorter in humid environments. I know that some people prefer to avoid washing down the sides, covering the pan, or micro-managing crystallization altogether, but this method is what I've found to be the best for me. I've also acidified my mixture at times with a few drops of lemon juice which acts (with heat) as a catalyst to convert the sucrose molecules in sugar to glucose and fructose, at which point it becomes an invert sugar and is less easily crystallized.

what sort of "contamination" are you referring to? I've always made my caramel with out a lid, without stirring or swirling and just brushed the sides with water. I've never really had an issue, but I also watched it like a hawk.