Do you mean glazes? Glazes are very watered down paints that you paint over an area, usually with the intention of either smoothing out the transitions between layers of paint, or with the intention of darkening the appearance of that area. I\'m sure someone else can explain it better than me.
sebrushworth [/b]has hit the nail square on the head.
Just dilute you paint until it\'s just a very fanit amount of colour and then it\'s the dilution you want.
It\'lll take several coats to achieve any difference in the effect on the under lying but it works well to add shading to the junctions between two areas.