My Opaque White has dried out, what can I do?

The ink of Opaque White may harden after being left open for a long period of time. It happens because while the container is open, the water particles inside the ink start to evaporate. If the ink is just a little bit stickier than before, you would still be able to use it after adding a little bit of distilled water and mixing it well. If it is completely solidified, you would have to replace it.