[brushwoodnursery]

I like to cover for 2 days after installing bees. After that, leaving it open is best unless there is extreme heat or cold.

 

[brushwoodnursery]

We found that leaving the observation hive uncovered can lead to the bees placing a lot of wax on the glass. So much so that you can't clearly see through it. We opened the hive, cleaned the glass off and switched to covering it, and didn't have the problem anymore.

Adam

That's more likely the bee space. Maybe after the cleaning, you replaced the frames closer to the glass.