room humidity and cure

how is it possible to lower the buds humidity into the jar to 60% when the room humidity is 70%?

From what I understand - it isn't. You would need to dehumidify the drying room or think about doing a dry ice cure - don't take that as 100% truth cause I'm new to curing too and haven't got a cure right yet but I haven't had the rh that high in my drying area and have not done a dry ice cure myself but I'm starting to think I should have - peace

A desiccant perhaps. Broveda salt/based humidity pack will maintain a constant RH.

If you're trying to drop rh with boveda humidipaks, buy the 62% or lower and don't expect miracles. They do work though.