How do yo tell?

Listen very very carefully. If you can still hear the ink in the bottle, you have some left.

Originally posted by jimmyb270
Listen very very carefully. If you can still hear the ink in the bottle, you have some left.

put a small piece of cork in the bottle if it dont float it is empty.

but i thought all invisible ink comes with a thermal strip on the side, you must have an old bottle i would replace it anyway. old ink tends to stain.

silent odorless tasteless invisible ink.

what's left?

mass, volume, texture...

assuming the ink is in a ballpoint pen or something:
Weigh the pen,
Write something with the pen
Weigh the pen

If it didn't get lighter you are out of ink,

not to mention you didn't write anything

Originally posted by iamatiger
assuming the ink is in a ballpoint pen or something:
Weigh the pen,
Write something with the pen
Weigh the pen

If it didn't get lighter you are out of ink,

Originally posted by phgao
C'mon, how much is a bit of ink going to weigh?

Originally posted by Bowmann

Originally posted by PBE6
Why is no one rec-ing this? Classic. Three recs for you, one for each post.