11.4 Light the candle and adjust the wick so that the flame is approximately 10 mm high and allow the lamp to burn for 5 min. Raise the candle until a smoky tail appears, then lower the candle slowly through the following stages of flame appearance: 11.4.1 A long tip; smoke slightly visible; erratic and jumpy flame. 11.4.2 An elongated, pointed tip with the sides of the tip appearing concave upward as shown in Fig. 2 (Flame A). 11.4.3 The pointed tip just disappears, leaving a very slightly blunted flame as shown in Fig. 2 (Flame B). Jagged, erratic, luminous flames are sometimes observed near the true flame tip; these shall be disregarded. 11.4.4 A well rounded tip as shown in Fig. 2 (Flame C). Determine the height of Flame B to the nearest 0.5 mm. Record the height observed. 11.4.4.1 To eliminate errors due to parallax, the eye of the observer shall be slightly to one side of the centreline, so that a reflected image of the flame is seen on the scale on one side of the central vertical white line, and the flame itself is seen against the other side of the scale. The reading for both observations shall be identical.