Chromic acid is not a popular cleaning solution, because chromium is classified as a carcinogen. It is still used occasionally despite the careful handling that it requires because it is effective at removing cloudy stains from glass that no other cleaner does. Using extreme caution, it is possible to make a chromic acid cleaning solution at home. The ingredients aren't available at your local supermarket, but you can purchase them online.
Place a clean, glass liter beaker in a glass pan to prevent damage from accidental spills.
Wearing rubber gloves, put 20 g of powdered sodium dichromate into the liter glass beaker.
Mix in a small amount of water to form a paste, and stir thoroughly with a glass stirring rod.
Continue to stir the mixture while slowly adding 300 ml of concentrated sulfuric acid to the beaker.
Carefully pour the solution from the beaker into a glass bottle with a stopper on top.