Silicon wafers were anodized in ethylene glycol containing . Luminescence, measured with a photomultiplier, began with oxide growth and, at constant current, increased with some low power of the voltage, the power depending on the type and resistivity of the silicon. When anodization was interrupted on low resistivity silicon and the voltage and current were decreased, then increased again, the luminescence was exponential with the voltage and linear with the current during this excursion. Initially, both the luminescence and the oxide growth on n‐type silicon of moderate or high resistivity were patchy; the patches gradually came together to form a uniform layer. With p‐type material the light emission was uniform even at the start. At the highest voltages, breakdown occurred with the appearance of “sparks,” which involve electrical discharge from the wafer into the solution