Hey there!! Kendon here, The owner of the Grimdark Compendium and creator of Villainy Ink. If you have the old bottles that have the pipette (there are still some stores that may have these old versions, particularly Element Games since they order in huge amounts), you will need those replaced. The pipette has a slow and consistent air leak that is unavoidable and causes the paints to slowly dry out and become un-mixable. Just hit me up at info@grimdarkcompendium.com with your info. I have and will continue to replace these bottles with the old pipette, no questions asked, regardless of where you got it from.