|Photo courtesy of Chill Designs Terrarium|
Chill Designs Terrarium offers a detailed terrarium care information via their ebay account. I found this tip on how to clean lime deposit from a terrarium very informative. This method would also be useful to clean bits of soil that cling to the glass as the layers settle in a jar.
"Terrariums are prone to developing a white line of lime-scale just above the soil line. To keep your terrarium looking like new, you'll need to clean this every now and then. How much lime-scale forms will depend on your water supply. To clean lime-scale from your glass container, take a wood satay stick and wrap a piece of moist kitchen paper (either moisten with water or a little non-toxic cleaner) and wipe around the inside of the container, cleaning away the lime-scale."