What are these crystals?

[brutus]

Wondering if you guys can help me out with what these little crystals are. Just racked a Cali Chardonnay off after completion of MLF and oak chips and found this at the bottom. Wine tastes fine, but is not very clear.

Thanks!
Steve



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[seth8530]

They are tartaric acid crystals. Sometimes known as wine diamonds. What happens is that as the while chills the acid starts to percipitate out and drop to the bottom of the carboy ( or bottle). They are no big deal, but you want to make sure they are done dropping out before you bottle. This will also lower your PH.

 

[WVMountaineerJack]

Hey Seth, Does it lower or raise the pH when you take out tartaric acid? pH scale is such a PIA! WVMJ

 

[sour_grapes]

Hey Seth, Does it lower or raise the pH when you take out tartaric acid? pH scale is such a PIA! WVMJ

Believe it or not, the answer is "It depends."
http://www.moundtop.com/pdf/Winemaking-TartrateInstability-rev2.pdf

 

[ibglowin]

It has always raised the pH on mine. You are removing acid through precipitation which will shift the pH value up a bit. pH can be a mystery at times with wine. As always YMMV.

 

[seth8530]

Yup you caught me, I meant that it would raise PH.. but it would lower POH (; . ...

Actually, I was not aware that there were exceptions.

 

[WVMountaineerJack]

I have to review the pH scale everytime I look at it, I am hoping my pH meter is dried up and corroded so I have an excuse not to use it! Seth that is one ****o in like 1000 posts WVMJ

 

[brutus]

Wow. That is quite the scientific answer!

I'm not sure the temperature has been low enough for cold stabilization, as it has hovered between 60 and 65 since primary.

Thanks guys!

Steve


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[seth8530]

I have to review the pH scale everytime I look at it, I am hoping my pH meter is dried up and corroded so I have an excuse not to use it! Seth that is one ****o in like 1000 posts WVMJ

Lol, what is scarier is that is just one of them that got found.. Now how many lurk under the waters yet to be discovered .... Now that is the scary part.

 

[cmason1957]

I have read that article about starting ph around 3.6 cold stabilization and whether ph goes up or down and I haven't been able to make heads or tails out of it. It just seems to me, from what I remember about chemistry, pH is related to number of hydrogen ions, if you remove some of those by precipitation of tartrate, then ph will always become a bigger number. But I could be wrong.

 

[Treeman]

The key is that Potassium bitartrate (KHT) is part of a buffer system and is an ion that can be an acid or a base depending upon the pH. If you think pH is hard to understand, buffers are even uglier, but I'll try to do it here without getting to technical.

At low pH buffer, KHT is a base, and tartaric acid (HHT) is the acid, so removing a base by precipitation lowers the pH of a solution. At high pH buffer, KHT is an acid, and dipotassium tartrate (KKT) is the base, so removing an acid by precipitation causes the pH to increase. The tipping point between the high and low pH buffers is around pH 3.9, but temperature and amounts of acid and other ions can shift this slightly ~ 0.1

Check out p7 of the link in post #4 for a more visual explanation of the buffer components, and why pH can change in both directions.

 

[seth8530]

Very interesting, thanks for the explanation, it has been a few years since I have been in a chemistry lab.

 

[Fsim]

I don't do a lot of whites but do these crystals form at such high temperatures? Seems kind of odd.

 

[seth8530]

They generally form at cooler temperatures. But, the rate of percipitation depends on the acid concentration and the temperature.