The invention relates to a composition for taking dental impressions, the composition comprising a siloxane component (A) comprising terminal vinyl groups, a siloxane component (B) comprising Si&mdash；H groups, a catalyst (C) being able to catalyze a curing reaction between components (A) and (B) and a silicone oil (D), wherein the silicone oil has a viscosity at 23 DEG C of at least about 600,000 mPa*s and is present in an amount from about 1 to about 20 wt.% with respect to the weight of the whole composition. The invention also relates to a method of producing such a composition and a method for adjusting the Shore hardness A of a composition.
