David Coffaro Vineyard and Winery Winemaker's Diary

Week 46
November 10, 2002 to November 16, 2002 

Wednesday November 13, 2002
I know a few of you have been anxiously waiting on the information concerning my new crisis. Well it took until today to collect all the info. 

A week ago I decided to make sure our Alcolyzer was giving us the right readings. Now some of you know that this is a $14,000 instrument and it should be reliable, but as all expensive things, they do need to be calibrated. 

I sent Brendan out to the local lab to buy an alcohol standard. He came back with a $60 sample which I thought was flawed and still do. Now for most people questioning a certified wine lab would be something to think about for a while and I was no exception. 

An alcohol standard is used to calibrate the Alcolyzer. The lab uses a method that is completely accurate? Certified buy all groups. I purchased an alcohol standard from this lab (V) last year and it was calibrated to 13.98%. I used that sample to calibrate the Alcolyzer. Gees, I said why not check out this old sample first. I had heard that alcohol goes down in value as it evaporates, but I have trouble remembering my Physics and/or Chemistry. SO I assumed that the reading obtained would be substantially below the 13.98 reading of last year. I even joked that maybe it would come out under 13.90. Brendan and I were amazed when we saw the reading of 13.94. That is close after one year. I assumed that our Alcolyzer was not reading correctly. Then I remember waiting to see what the new sample would show. I was more shocked: it read 13.85. How could it? I was told that alcohol does not go up in value. So if the old sample read .07 percent higher than this year, how could V have done the same analysis. 

I need to take a break to see a movie with Pat so I will be back soon. 

Friday November 15, 2002

Well, Pat and I have watched two movies the last two nights so I have been busy. Now to continue with the Alcolyzer story: 

I called V and asked how the old sample could read higher than this new one and they had no answer. I asked them to do another test with their alcolyzer instead their GC which is a different method. That reading came back at 13.90 for the new Standard; so I used that reading to adjust my alcolyzer. I then did a few samples of our new wines and found that the readings were coming out about 0.1 higher. I still suspected that V was giving me readings that were off. I decided then to take a reading on my 2000 Carignan. That wine reads 13.9 on the label. I was shocked to receive a reading back that read 14.20. How could that be? In January of 2001 I had V do alcohols on their GC for all our 2000 wines. The Carignan was reported as 13.97 then. I also took readings on many of my other 2000 wines and found that they were also higher than with the GC last year. I then decided to send a sample of the 2000 Carignan to V to get a new GC and an alcolyzer reading. I waited anxiously. I was even more surprised when the alcolyzer reading came back at 14.20, exactly what I got on my alcolyzer. What was more surprising was that the reading I received for the same wine on the GC was 14.30. Now how could we get a reading so different than last year. Alcohol does not go up in value. It sure would not go up by 0.33%. I was quizzed by V asking whether I had the right sample or whether there were bottle variations. I checked another bottle and got the same reading. There is no answer for this mystery. 

As a closer I sent the sample of the Carignan to a different lab. With a different method (similar to my alcolyzer) I received back 14.20% the same as my alcolyzer. So I am happy, sort of. Can certified BATF Labs make mistakes? Do readings vary normally? I have been told by others that the accuracy of these GC tests can vary by .2 or more. All I know is my alcolyzer gives me the same reading on a sample every time. Now all I have to do is find an alcohol standard I can depend on! 


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