Improved very high viscosity (putty) two component polymerizable polyorganosiloxane composition for use in making dental impressions, having improved tear strength, handling and wettability. Improved tear strength results from inclusion of a quadri-functional polysiloxane having a vinyl content of 0.16 to 0.24 m-mole/g. Working time is maintained by including sufficient amounts of a retarder composition that delays onset of the vinyl polymerization. Handling is improved by the addition of a very high viscosity linear vinyl terminated polydimethylsiloxane which reduces tackiness and improves the shelf stability. Wettability is improved by including a surfactant resulting in a surface contact angle with water at three minutes of less than 50.degree.. The surfactant chosen has an HLB of 8-11, such that the wetting contact angle is achieved within less than two minutes and remains wetting throughout the working time of the impression taking, substantially improving the impression making process.