Our diocesan liturgy director provided some helpful instructions on getting “cloudy” glass vessels looking spiffy for Easter.
You will need vinegar, ammonia, dish soap, and a denture-cleaning tablet.
Fill the empty cruet with vinegar or ammonia, and let it sit at least 30 minutes or overnight for tough buildup. For tougher stains, follow that up with lukewarm water and add a denture-cleaning tablet. Allow it to sit for 30 minutes or overnight.
Rinse the cruet thoroughly with hot water.
[You can clean tougher stains with lime cleaner (Lime Away) according to the package instructions to remove tough mineral buildup, but make sure to follow any safety precautions in the instructions for cleaning after using it. Rinse out the cruet with hot water, and add 2 or 3 drops of dish detergent to clean it.]
You can follow this up with a cleaning in the dishwasher.
Shake out any excess water and dry it thoroughly with a towel.