Stratasys J850 Manual page 127

Soak models in a 1-percent solution of caustic soda (sodium hydroxide) to
remove Support material from difficult-to-reach areas and to give the model a
smooth, clean finish. The amount of time you soak the model in the solution
depends on how delicate it is and how much Support material needs to be
removed, but it is typically between half-an-hour and several hours. In any
case, you should remove as much Support material as possible before the
caustic soda treatment, and rinse the model thoroughly (with a water jet)
afterwards.
Soak models in a 2-percent solution of caustic soda (sodium hydroxide) and
sodim metasilicate (Na SiO ) to remove Support material. The amount of
2 3
time you soak the model in the solution depends on how delicate it is and
how much Support material needs to be removed. Rinse the model
thoroughly under running water afterwards.