To change the amount of air in your Sand Art, simply use any injector with a 27 Ga (0,4 x 20 mm) needle (not included in the package for safety and legal reasons).
However, you can buy it separately through this link: https://sandarthome.com/products/injector
Find the sealed hole on the frame of your Sand Art and insert the needle.
This way, you can add or remove small amounts of air until you get the desired quantity.
The air level will usually be right when you receive your Sand Art. Only regulate it if you feel like the sand is not flowing at the right speed no matter how you flip it around.
In most Sand Arts, we will include an instruction sheet for you to have a better viewing experience.