brix level for ripe niagara

Friend wants to pick his Niagara grapes, is there a specific brix level they should be before harvest?

Is there a general range for all grapes or is it dependent on variety? I'd really like to find a chart that gives recommended brix levels for different grapes.

Specifically, concord, stuben and niagara.

Thanks,
schoolmaster

For best Wine results -- grapes are picked at the peak of ripeness... You want to maximize sugars for wine.

The absolute best you can do is to wait for the stem entering the grape to die -- that way, you know it can't get any more sugar in there....

Then, on specific brix -- it is so heavily dependent on the soil, nutrients, fertilization, rainfall, plant itself, and the year, etc..... A grape that can run 21-23 brix one year may only go 13 on a subsequent year if you give it too much nitrogen fertilizer at the wrong time and you get big, watery grapes.... If you get too much late season rain or you neglect soil minerals (Calcium, magnesium, phosphorous, potassium, minor elements, etc...)... You get the picture....

Personally, I like to wait for the stak to die and the grapes to start shriveling a wee bit.... Not raisins, but just starting to shrivel a teeny bit... When you taste them -- your impression will be "These taste Sweet!"

Thanks

John