Tag Archives: Refractometer

Veraison color vs sugar content



As some of you may have heard Sonoma Valley is ahead of schedule this year for version and probably harvest by 1-3 weeks.  Here at Turtle Vines I think we are 1 week ahead of last year given all the clouds/fog the last 2 weeks.

We are about 85% into version with some vines still having green grapes.  I decided to test the sugar content of the grapes at different colors to understand how it correlates.

Green grape – 8%
Orange grape – 11%
Purple grape – 15%

Dark grape on the same vine where all the grapes have turned is 16.5%.

The rule of thumb is that the grapes shift by 1% per week in “normal” weather. If most of the grapes in the vineyard are around 16.5% and I want to pick at 24%, then I’m 7.5 weeks away, or 9/23…same as last year.



RefractometerIt has finally come time to measure the sugar content of the grapes, hope they ripen evenly and then harvest and make wine.

Think back to your chemistry days where you had different tools to measure chemical content of liquids….or is that only me with my Chemical Eng background? Anyway, there is a very simple tool called a Refractometer that will measure the sugar content of the grapes.

In the picture above you can see that you simply squeeze the grape and put the liquid on the glass window and cover it with the lid. Then you look into it like a kalaidascope and a line will appear on a scale and you will know the content. Hard to explain on paper, but easy to do.

In the vineyard you now have to measure a good number of samples every week until you get to the desired sugar level. I’m shooting for 23.5% that will give me a wine with a little under 14% alcohol.

In addition, for the flavors you can tell if the grapes are ripe by the color of the seed. If the seed is green it isn’t ready. If it is brown…..good to go.