White Vinegar

• White vinegar is the most common acidic cleaning solution for glassware. White vinegar is a very mild acid that is also food grade and completely non-toxic. Because of this, it is preferable over the more common ammonia-based glass cleaning solutions. To use it, mix one cup water with one cup white vinegar and clean the glassware with it.
  
  

Lemon Juice

• Lemon juice is another mild, natural and non-toxic acid that is capable of cleaning glassware. However, you do need to rinse lemon juice from the glassware to prevent it from making the glass sticky. To use it, boil lemon juice in a pot until it has reduced by half. Apply the thickened lemon juice to the glass until it is completely clean. Rinse the glass with water and dry it until the water spots are gone.
  
  

Oxalic Acid

• Oxalic acid is an extremely caustic acid that is strong enough to dissolve rust from glass. You should always mix oxalic acid with water until it reaches a solution that will not harm the glass. Follow the manufacturer's instructions for how much water to use in the solution. If you don't do this, the oxalic acid could actually etch the glass. You should generally only use it to clean outdoor glassware such as glass light covers or glass insulators. Be careful whenever using it to not get it on your skin or in your eyes. Use it only after all other cleaning options have failed.
  
  

Alternatives

• There are some basic solutions that can also clean glassware. These are just as effective and safe to use on glassware. They generally contain ammonia, which can be toxic if you ingest it. Ammonia can also create a toxic gas if you mix it with bleach. For this reason, some homeowners choose not to use it.