strange problem with SnJ Aluminum

Has anyone experienced a problem like this with SnJ aluminum? I have a 1 oz. bottle that's a bit less than half-full that has "separated" into 3 distinct layers. On top there is a clear solvent, then a milky white semi-solid layer and at the bottom there is the silver pigment. The silver pigment doesn't look like it originally did however; it is very granulated. Overall, it looks really weird. Nothing at all like it did when new. It was used only once or twice and then put away. When I checked it again, months later it looks as it does now. It is completely unusable. Any ideas out there? thanks all, Gary .