A practical exercise for developing a simple cost-effective solar ultraviolet radiation dosimeter is presented for use by middle school science students. Specifically, this exercise investigates a series of experiments utilising the historical blue print reaction, combining ammonium iron citrate and potassium hexacyanoferrate to develop an ultraviolet sensitive solution. The activity is intended for implementation into courses of study based on the new Australian science curriculum, and the strand chemical reactions matter. The activity investigates rates of reaction and examines the influence of an invisible physical catalyst, solar radiation. The developed photochemical dye was tested for use as a solar dosimeter by painting or soaking various common materials with the solution. A soaked cloth dosimeter was determined to be the most practically appropriate. Its use as a "magic cloth" or polyethylene filtered ultraviolet radiation dosimeter, capable of being calibrated to incoming solar radiation is discussed. The exercise is presented as a practical guide that can be followed by middle school aged science students beginning studies in physics, chemistry or the environment. The experiment may also be extended and applied to senior chemistry investigations. (Contains 3 figures and 1 table.)