We Americans expect wines to be clear and bright, with no precipitates. This can be an issue for small wineries like PV, however larger wineries can fix this (more below).

The crystals are Tartaric acid - sounds scary, but have no fear, it's not. The chemical formula is C₄H₆O₆. This is also known as "Cream of Tartar" - yes, the same stuff in your kitchen that you use in baking! It is absolutely natural. (See also Wikipedia entry: Tartaric Acid in wine).

The larger wineries are able to remove this sediment fairly easily. By simply cooling the wine down to just about 30F (the wine won't freeze at this temp due to the alcohol content), the tartrates will crystalize, and attach to the walls and bottom of the tank. The wine is then allowed to return to room temperature, and then "racked". Racking is simply pumping the wine from one tank to another. This moves the clear wine out, leaving the crystals behind. Scraping those crystals out so the tank can be used again is nuiscance, but that's a different story!

In order to cool the wine, larger wineries will have a double-walled tank with coolant (typically glycol - same stuff used in your cars anti-freeze) run through it. This chemical never contacts the wine, it is only run through the outer sleeve of the tank. Glycol remains liquid even at temperatures below 32F, which makes it perfect for doing this cooling operation.

So - after all that explanation, here's why PV wines often have visible tartrates. PV cannot afford a double wall tank, let alone afford a glycol chilling system!

The wine is just fine, simply enjoy it, but pour carefully when you reach the bottom of the bottle, leaving the crystals behind. If a few make it into your glass, you may wish to rinse before moving onto to another wine.