That's easy. Humans consider it ripe about 2 days after the raccoons
get it. g

Or about 18-25 days after pollination.

Do you know how to pick "store corn" by examining the silks and
feeling the kernels through the husk? If so, just use the same
technique. Otherwise, pick one ear as your sacrificial ear...
pull back husks a bit near the tip and squish a well developed kernel.
You're looking for a kernel in the milk to very early soft dough stage
-- you should get a milky, sweet juice squirting out from the kernel
you've punctured. If it's more like a dough than milk, it's a little
late for most people to enjoy as sweet corn.
Agronomists would call the "good stuff" in R3 or early R4:
http://www.ag.ndsu.edu/pubs/plantsci...m#Reproductive


If the kernels are not well filled and the juice seems watery, replace the
husks you've pulled back and try a different kernel the next day, until
it's at your desired degree of ripeness.

Then compare the colors of the silks beyond the husks and just at the very
tip, barely inside the ears. The silks will be pretty dry and brown
beyond the husks, but still yellow-white just as they get to the husks.
Outer husks should be dark green.

Find another ear in your corn patch that looks similar to the test ear
in feel of the kernels through the husk, husk color and silk colors.
Pick that one and have it for lunch. If it's the ripeness you like,
you now know that you can recognize ripe by the silk and husk color.

Leave that sacrificial ear unpicked and test a kernel every day -- you'll also
soon find what "past its prime" looks like.