Help with leaf electroscope for school use please!

[msr777]

Hi all

I've just had a couple of new leaf electroscopes delivered to a school here, bought cheaply online.

They deflect and charge very well but discharge almost immediately when contact is broken. Is this to do with the humidity in my room? If so, would it help to:
use tape to seal where the glass windows slot in?
use one of those silica drying sachets inside before sealing?

Thanks for any advice!

Sorry if this is inappropriate here, but it's the first place I thought of for quick advice.