I never expected so many responses when I wrote the original message!
Thanks to all who replied.
Here's an update.
24 hours ago, ants were lined up 10 deep, around my bait, which was
laid out on the counter in the kitchen. The Boraxo/grape jam/water mix
was spread out over quite a large area, there must have been a
thousand of them on that counter!
Last evening however, they started to thin out.
By this morning, not a single ant was seen on the counter in the
kitchen! We have been doing household chores, and have been watching
the counter top all day. We have not seen an ant all day!
So, I conclude that Boraxo/sugar works fast on carpenter ants (less
than 24 hours). With regular ants, it appears that it takes 2.5 days
to exterminate the little buggers.
So, we have an ant free kitchen again. I've left out some plain sugar
water for them, and will watch it over the next couple of days.
Again, thanks to all who wrote and replied. I might check out Boric
acid, but since Boraxo seemed to work, I'm not sure whether I need
Boric acid tho.
Art in Maine