Wine Diamonds – Crystals in Your Wine

cork_tartratesWelcome to our second blog celebrating all things Zinfandel in November.  November 18th marks National Zinfandel Day, and if you are looking for a way to honor this 5th annual tribute to America’s Heritage Grape, might we suggest digging out a bottle of any 2007 Scott Harvey Zinfandel and mine some wine diamonds of your own.  What are wine diamonds you ask?  Read on to discover just how truly special these grainy bits of sediment really are.

In 2011, Scott wrote a blog, featuring an article from Dr. Richard Peterson, about tartrates in wine.  While tartrates are not exclusive to Zinfandel in general, it does appear that all of our 2007 Zinfandels are displaying these “wine diamonds”.  Read on for Scott’s and Dr. Peterson’s fun and witty interpretation on why these crystals may just mean you’ve struck a little of California’s liquid gold.

“Our 2007 Mountain Selection Zinfandel has developed tartrates in the bottle.  This article does a wonderful job explaining the formation of tartrates (wine crystals) in wine and the resulting effects. It is written by my mentor, Dr. Richard Peterson.  Dr. Peterson is one of California’s most respected winemakers and has made many contributions to the wine industry.  He invented the Peterson barrel rack, giving the technology to the wine industry with no financial gain to himself.  Well over 90% of all barrels today are stored on Peterson barrel racks.  He has been the head winemaker for wineries such as, Gallo, Beaulieu Vineyards, Monterey Vineyards, Atlas Peak, and Seagrams Wine Group.  He hired me to be the president and winemaker of Folie a Deux and helped in the development of Menage a Trois.  Today he is a shareholder of Scott Harvey Wines and sits on our board of directors.  The article is titled;


No ma’am, the crystals on the cork aren’t red diamonds—we couldn’t sell the wine at this price if they were.  Neither are they red glass, chemicals, or anything dangerous at all.  They are pure, natural CREAM OF TARTAR crystals: the same cream of tartar that you use in cooking!  They sometimes appear inside a bottle of wine after storage, especially cool storage.  BUT, ONLY IN FINE WINES!  They have a slightly sour taste, but—because they don’t dissolve very fast in your mouth—they’re really more “gritty” than anything else.

Tartaric acid is quite rare in nature, yet it is the major organic acid which occurs naturally in grapes.  With one exception (Tamarind), grapes are the only economically significant fruit crop to contain relatively high concentrations of tartaric acid!  Grapes are also naturally rich in potassium and , AS GOOD AS THAT IS FROM A HEALTH STANDPOINT, it often leads directly to unsightly crystal formations in fine wines.  For, whenever you have potassium and tartaric acid together in solution, they quickly figure out how to become potassium bitartrate—the scientific name for cream of tartar—which then crystalizes out.  Since the cream of tartar is even less soluble when cold than warm, chilling the wine increases crystal formation.  (You sometimes find that a bottle of wine looks okay in the store, but in your refrigerator a crystalline sediment of cream of tartar may form in the bottle.)


Cream of tartar is certainly not harmful, but the American consumer has been conditioned to suspect any product with sediment, especially wine, and is inclined to discriminate against such products.  Wineries, therefore, often chill new wines to just above the freezing point (around 23 degrees F.) at which time the crystals form and settle to the bottom of the tank.  The wine is then racked and or filtered while still cold, to insure that the cream of tartar crystals are removed, no matter how small they might be.  Then, after the wine is bottled, the consumer can chill the wine for serving without fear of new crystals forming.  This process, called cold stabilization of white wines, is usually routine in all fine wine regions of the world since crystal removal doesn’t affect the taste of white wines.

Not so with red wines.  Chilling reds may cause pigments, tannins, and other components of wine “body” to drop out (along with the cream of tartar); the resulting wine “loses something” and just isn’t as good as before.  We don’t chill our red wines for this reason.

Do you think we should?  Scott Harvey, having been European trained, makes the Scott Harvey wines more in the “Old World Style”.  They tend to have higher natural acidity.  Thus, there’s a greater chance to see crystals in our wines than in those wines produced more in the “New World Style”.  Will the consumer know that only the finest wines can form crystals*— and learn to accept them (decanting the wine)?  Or, will we be forced to cold stabilize and run the risk of reducing some wine to mediocrity?  Only you can tell us.

* Lesser wines always have lower natural acidity;  too low for any excess to crystalize out of solution.  They CAN’T produce crystals.

Dr. Richard G. Peterson –


The 2007 vintages of Scott Harvey Zinfandels seem to have all developed “wine diamonds”.  This includes our 2007 Mountain Selection Zinfandel, 2007 Old Vine Zinfandel, 2007 InZINerator and the 2007 Vineyard 1869 Zinfandel. When you open a bottle of what are now library wines, you may notice crystals on the cork.  Since the bottle is now opened, go ahead and try it.  Many people have written us to say that we’ve produced the best and most unique Zinfandel they’ve ever tasted.  We hope you think so and can live with microscopic diamonds on the cork.  Noted author Hugh Johnson (“Wine”) says the following:

“It is remarkably hard to convince people (especially in the U.S.) that sediment in wine is harmless and natural and untampered with.  If wine has been pasturized, put through very fine filters or otherwise denatured, IT IS POSSIBLE TO AVOID SEDIMENT.  But it is no longer natural wine: it seems too high a price to pay to avoid the chance of a speck (on the cork or) in the bottom of the bottle.”

Scott Harvey






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  1. This is definitely a very informative post. My wife and I keep discussing these things when once we bought an expensive wine only to find out that there were red crystals on the cork! We never drunk that wine because we were afraid that they might be broken glasses. We were so ignorant! It’s a shame.):