Hi all

I recently installed a new bathroom vanity, sink and faucet. I am
getting a small leak at the point where the large nut tightens the
drain assembly onto the bottom of the sink, compressing the black
washer onto the bottom of the sink drain.

I have seen sink installs before, checked the net for hints, and even
did a couple quite some time ago. I double checked the sink/vanity
that was removed from the space, and also on line, so I know the
washers on the drain assembly are in the right order. The drain
flange has a good ring of plumbers putty under it.

The sink itself is an ornamental handpainted model, and may have some
slight irregularities at the sink drain. Because the sink is somewhat
more delicate than the standard white porcelain models, I don't want
to risk overtightening the nut.

So what I am hoping to get are pointers on what the plumber-savvy
folks would do to handle a leak on the underside of the sink drain?
Can I add a thin bead of plumbers putty where the black washer meets
the sink, in an attempt to fill any irregularities the washer can't
handle? I am reluctant to use silicone at that point, just in case it
isn't successful and I have to dismantle it again.

Thanks for any tips