I posted recently about how to preserve open bottles of wine indefinitely by freezing. I mentioned that there is one potential problem.

Before most wines are bottled, they are chilled to below freezing in order to remove a substance commonly referred to as, tartrates. In white wines tartrates can look like glass crystals or a darkish colored sand. In red wines they take on the color of the wine and can just look like red muck. They are harmless. ( The substance ia actually potassium bitartrate, also know as cream of tartar, a key ingredient of baking soda). When this is done in the winery, the tartrates drop to the bottom of the tank and the wine is then racked off the crystals, filtered and bottled.

Many wineries don’t do a great job stabilizing wines before bottling, so if you freeze a bottle (or even just chill it), you will ‘stabilize’ the wine and tartrates will drop out of the wine in the bottle. It is a bit unsightly, but completely harmless. When I have a bottle with tartrates, I stand the wine up for ten minutes and then decant the wine or just carefully pour it into the glasses. The crystals will stay behind in the bottom of the bottle.

Tom wrote to me several months ago asking about what was in this picture and despite the fact that this is yucky looking, I advised him that it was just harmless tartrates.

So, Freeze, let the settle, if there are crystals, just decant it. Still the best way to preseve an open bottle.