Why does my wine have crystals on the cork?

Question...I opened a bottle of white wine that had some crystals on the bottom of the cork and in the bottom of the bottle.  What is it?  Are they harmful?

Answer...The crystals are the result of tartaric acid, which is the principal acid in wine made from ripe grapes.  They are not harmful and are natural deposits of the wine. 

This suspicious looking substance is also know as cream of tartar.  It is a by-product of the wine used in the manufacture of baking powder.  If you an accumulation of cream of tartar crystals in a bottle of wine, you need only allow the material to settle to the bottom of the bottle before carefully pouring off the clear wine into a clean, fresh container.  Then you can enjoy your wine with complete peace of mind.

By the way, here's a little household hint for cleaning a greasy aluminum pan with cream of tartar:  Add one tablespoon of cream of tartar to the pan filled with water and boil it for a few minutes.  Rinse and wipe clean!

Wine works wonders, even with its by-products!

A side note about Mountain Spirit Winery's wines as it relates to this subject...

Many people who frequent our winery and purchase our wines know that Mountain Spirit Winery always performs cold stabilization on all our white wines.  In this process, we drop the temperature of wine in a tank almost to the freezing point, at which point we add potassium bi-tartrate crystals to encourage precipitation of the tartaric acid.

Over several weeks, the tartaric acid crystals precipitate to the bottom of the tank.  We then "rack" off the clean wine, leaving the crystals behind.  We then do freeze testing of the clean wine to be sure all crystals have precipitated.

It is absolutely true that the crystals in the wine do no harm, but they can be distracting, especially if someone is not certain why they are in the wine they are consuming.  We have heard stories about customers thinking such crystals are glass!  For similar reasons we also heat stabilize our white wines to remove excessive protein which can form a haze in the wine.  We would rather not have anything take your attention away from just enjoying our award winning wines!

Phew!  That's about all the chemistry I can stand right about now.  Time for a glass...

Mike