I bought crackle paste. Sealed it up very well after using only a tablespoon. Half a year later I returned to the jar, and it was hard, dried up & ruined. Not a direct answer to your question, but once you start using it, my impression is that you have to use it up in a short-ish time span.

@@stephaniek2913 Thank you, but that's not working time. I've used molding pastes in the past but want to travel to my local store to buy it. I don't want to buy several different jars - that gets expensive fast! - so I'm asking here what the working time is for each one. If I'm doing a raised stencil on a drawer front or on a wall the working time is extremely important. (Some wall stencils are huge.) I've used an extra heavy paste before that set up almost immediately. It was frustrating. I want a few minutes to work with it but not have to wait an hour for it to dry. I also need to be able to sand it once it's dry. Some molding pastes are more ike plastic when dry and not very 'sandable'.