The nature of a screen has an important effect on two main aspects of continuous fugal performance, the molasses removal rate and the loss of sugar to the molasses. In particular, screen corrosion (Greig et al., 1984a and Kelly et al., 1985) can cause large changes to a screen, and thus to its performance. The results of flow measurements through screens (Greig et al., 1984c) provide the basis for a mechanistic model for predicting molasses removal rates. A key assumption in the model development is that the screen represents the dominant resistance to filtration. The effect of screen condition on sugar loss was examined by studying the crystal retention properties of screens in a laboratory apparatus. The technique and some initial results are presented.