Your glow coasters can be set at lower or higher intensity depending on how much light you expose them too.
Method 1: Make sure your glow coasters get general daylight through the day, this will give them enough charge to show you where your bedside drink is for the entire night.
Tip: When you use your glow coaster to light up a bedside drink make sure it is clear glass or clear plastic so that the glow light can pass through, otherwise you will block most of your light unless you have the large coaster.
Method 2: Hold your glow coaster at about 50mm or 2 inches from a strong light (See pictures) for about 15 - 30 seconds, this will bring them up to a super charged level that will last for hours. If you want super brightness leave it on a window sill or even better outside under the direct sky to soak up the solar rays for around 5 minutes about an hour before Dusk, then hold it next to a light before bed.
You cannot use these glow coasters in the same room as a star ceiling or it will drown out most of your stars, if you want to have it in the same room you will need to place it under your pillow or in a draw when viewing the stars.