Behaviour of Salt Core

Dear All,

I have a basic question, which i am confused of so any input or clarification will help me to understand better.

Actually, i have a compacted salt core which is very stable at STP conditions(Non-hygroscopic). Then, I expose the same salt core to pressure ~ 1500 Psi & Temperature of 200 F for a period of 24 hrs (say) and slowly cool-down the temperature to room temp and release the pressure to Atm pressure. My observation is that the salt is going unstable means, I see the surface getting greasy/watery (zooing out some water from the matrix of salt). Which is simillar to hygoscopic salts absorbing water from atm. but my question is why is not happening before i expose the same salt to pressure if the salt is actually hygroscopic.

Am I de-stabilizing anything with respect to the salt core. you inputs are highly appriciated .

bala....