A fantastic and interesting article I came across while researching simple glazes – http://www.ceramicstoday.com/articles/alternative_materials.htm
Not only do you get to learn some of the basics of creating glaze but you learn some interesting methods of sourcing the base materials. It still amazes me that thousands of years ago our forefathers discovered that burning clay and using copious amounts of wood ash would produce a primitive glaze. It was all over from there and we’ve been experimenting ever since.
Basic glazes are made up of clay, feldspar, silica, whiting, dolomite, talc, colorants, etc. And here we have an article going into the alternative materials. Our ancestors had to dig this stuff up from the ground. Now we can just go purchase from a ceramics supply store or experiment with “nonstandard” materials which can be purchased from the local hardware or drug store.
Another nice site for recipes is here – http://glazerecipes.wikispaces.com/