The key to good results is careful and exact sample preparation. Prepare your samples so that the amount of substance is the same across all capillaries. Slight differences in the amounts could cause deviations in the measured melting point temperatures. Check the capillary fill height using the lines marked on the melting point sample preparation tool. For accurate measurements, the optimum fill height of 3 mm should be observed. The sample preparation tool offers many possibilities for checking the fill height of your substance. See Fig. 1 for an example of estimating various fill heights. For best results, it is important that the melted substance covers the holes for transmission light detection.