Tartrates are a natural occurance in wine, most all wines have them
initially. In the industry we refer to this as the wine "throws a
precipitate". A common nickname for it is "Wine Diamonds". These
solid crystals will appear in a layer on the bottom of the bottle, and
may also be in a layer on the bottom (the wet part) of the cork.
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
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
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