The best way to clean cloudy or foggy handcrafted glass is to do so as gently as possible. If warm water and a soft rag won't cut it, we recommend using a vinegar and warm (not hot!) water solution. Never put your beloved Blenko in a dishwasher!
Fill the glass item with equal parts white vinegar and water, using enough liquid to cover the cloudy area. Allow the liquid to sit for a day, and then clean the glass with a nylon scrub pad. If the item is too narrow to reach into, place a handful of uncooked rice in the bottle, swirling it around with the vinegar.
Always remember to avoid harsh cleaning solvents like ammonia, bleach, acetone, and any sort of acid that could cause pitting or abrasion.
Unfortunately, oftentimes improper use or cleaning of handcrafted glass leads to permanently foggy glass, or "sick" glass, due to the soft and slightly porous nature of soda-lime glass.