Four different brands of alginate impression materials were mixed by hand and ten impressions of each were made of a block for detail reproductions. In addition, two different mechanical devices were used to prepare one of these alginate impression materials. Thus a total of six groups was tested, with ten impressions per group. Stone casts of these 60 impressions were compared by the line study method and the number of surface defects. A statistical analysis was performed on the collected data. The results indicated that the Whip-Mix vacuum mechanical spatulator produced significantly superior results to the Columbus system centrifugal mechanical spatulator, and that among the four alginates hand mixed, the Jeltrate impression material gave better results.