A chemical reaction occurs where has bubbles form, and when you try to shove the brush back in, it explodes all over your face and business formal shirt. It bled everywhere and bubbled and completely leaked out of the tube, the picture below is what it looked like AFTER I cleaned up most of the liquid.
You can safely put saline solution in though. If it gets too dry and clunky. This, I have tried and tested.
As you can see below, this is me experimenting with my regular Covergirl Lash Blast mascara in blackened brown.