The true raw meal to clinker factor is given by: 1/(1 – Loss on ignition of kiln feed). It is normally about 1.55. The major variation from plant to plant arises because of the dust loss from the kiln feed, which varies from kiln to kiln dependent on the collection efficiency of the top stage preheater cyclone. Also dependent on the handling of the dust. If all the dust is sent back directly to the kiln then the factor should be 1.55. If the dust is added to the kiln feed silo then the formula will be: (1/(1 – LOI kiln feed))/(1 – Top Cyclone Collection Efficiency).