Variously colored glass artifacts from the Islamic sites of Rayy and Istakhr (northeastern Iran) were examined by PIXE analysis, with particular emphasis on the detection limits for the trace elements influenced by the matrix constituents and colourants used during manufacture. In view of the complexity and diversity of glass composition, the PIXE analysis procedure was organised as a four-step process. The configuration of the proton beam energy was changed to allow groups of elements to be determined as follows: a) sodium to calcium; b) potassium, calcium, titanium, chromium, manganese, iron; c) iron and heavier elements but also minor and trace elements of importance in glass making (zinc, tin, antimony, lead and bismuth) and finally d) glasses with more than 5% lead, and determination of silver, tin and antimony when at trace levels only. In this way it was possible to determine raw ingredients, the glassmaker's palette, and patterning among trace elements (0.1%). Table, pixe detection limits, references.