Bubble sizes were measured for molten wax-nitrogen systems using photography and dynamic gas disengagement. The effects of operating conditions, system geometry and wax type were studied in 0.05- and 0.23-m-diameter by 3-m-tall bubble columns. Both techniques were used with FT-300 wax, while only the dynamic gas disengagement technique could be used with reactor waxes due to their dark color. For FT-300 wax, Sauter mean diameters obtained from photographs taken near the column wall were significantly lower than those obtained from photographs taken near the center. The ds values obtained from dynamic gas disengagement and photographic (near the column center) methods, for this noncoalescing medium, were in the range 0.5–1.6 mm in the large-diameter column. For reactor waxes, ds values were significantly higher (1–2 mm for Sasol and 1–5.5 mm for Mobil's reactor wax) and are in agreement with results reported in earlier studies with similar waxes (ds = 2–4 mm), where different experimental techniques (light transmission or hot wire anemometry) were employed.