Crystals in my 1997 Guiraud?

I should wait for the chemists, but I'll try to answer. They are tartrate crystals. Pretty common in unfiltered wines, sometimes especially if the wine went thru a real cold spell. Totally harmless, just treat like other sediment. I've never noticed any correlation between tartrates and color of remaining wine; but that's not to say there is none. Dale

Dale Williams Drop "damnspam" to reply

Right

There are a few ways of removing tartrates, but filtration in itself is not going to make any difference. But yes, cold will precipitate them. So if you wine was not treated to remove the tartrates a cold spell will make more crystals appear.

Right. Some people like to see them because it means the wine has not been messed about with. The main reason to remove the tartrates is that consumers think there is a problem. The other reason is that they make the taps in wine boxes leak!

Can't think why there should be one. A dark colour suggests oxidation and possible exposure to heat.

Dvorak,

the other posters are correct as to the crystals being tartrate. These occur especially in wines like German and Alsatian rieslings (haven't seen in Austrian yet!) and Sauternes. They are harmless, but try NOT to swallow them with the wine: they are very bitter tasting and will probably ruin the sweet wine experience.

Mark S

According to Ronald S. Jackson's "Wine Tasting: A Professional Handbook" (2002 Academic Press at p. 29), flake-like crystals are likely potassium bitartrate and fine crystals likely calcium tartrate. Calcium oxalate also sometimes forms. There can also be crystals from calcium salts of saccharic or mucic acids (produced by Botyritis cinerea).

As an aside, it's almost funny to see how newbies react when they see salt crystals in their glass. Even after you explain to them what they are, they give the wine a skeptical look.

Thanks everyone...I knew what they were - I just couldn't recall the name. Like I said, I've seen them plenty of times in many sweet white wines. I was just wondering if the fallout of them in my 1997 Guiraud was somehow actually related to the dark color of the wine. To be truthfull, I always eat them once the bottle has been finished off and the aftertaste gone. To me, it's part of the complete experience. I found that as long as the wine was good, their flavor really isn't too bad.