How can copper(II) sulfate crystallize outside a glass vial?

I'm making copper sulfate crystals in glasses. Within a few weeks, the copper sulfate seems to crystallize both inside and outside the glass:


(A few weeks after making a new solution)
[![enter image description here](https://i.stack.imgur.com/ytHul.jpg)](https://i.stack.imgur.com/ytHul.jpg)
(Yet another few weeks later)
[![enter image description here](https://i.stack.imgur.com/aVu4Q.jpg)](https://i.stack.imgur.com/aVu4Q.jpg)


How is that possible? The glasses haven't moved for all those weeks. Is that pure capillary action, or is there another phenomenon?


