This is every lash artist secret weapon to keep their eyelash extension adhesive in line! If you are not using a hygrometer in your lash space you should be! Those days you wanna pull your hair out because the adhesive is acting "different" than the day before, here is why:
Eyelash extension adhesives (Cyanoacrylates) cure (turn from a liquid to a solid) from the moisture in the air. We talk about this more in-depth in this post.
The best way to keep your adhesive working on point is to keep your humidity and temperature in a good range and to measure them with a hygrometer.
Recommended room humidity on average is 40-60% (this can vary with different adhesives).
Room temp: If you are comfortable in the room, your adhesive will be also. In cold temperatures your adhesive thickens, in hot- it becomes more runny so keep your room at a comfortable room temp, around 70-75 degrees ferinheight.