Impression materials show shrink during polymerisation. The average shrinkage of C-silicon impression materials is 0.6-1% after 24 hours. The A-silicons show 0.15-0.2% shrinkage after 24 hours. Like in other chemical reactions, the ratio of the ingredients and the mixing can strongly effect the final properties of the polymerised material. In their study the authors compared the shrinkage of Promodent ASK low-viscosity A-type silicon impression material using hand mix and cartridge mix technique. The measurements were carried out according to ADA 19 specifications. The statistical analysis of the results did not show significant differences in the shrinkage between the two mix techniques after 30 minutes, 24 hours and 72 hours.