Originally Posted by jpmain
Thanks for the feedback. I suspected as much but was hoping for some other opinion to support my amateur one. The original sinks did have an overflow and these do not.
Is there a proper way to add a vent to the stack?
The problem isn't that your drain is or isn't vented. I'd bet it probably is. The water is airlocking in the bowl itself, not necessarily due to a lack of a vent in the drainage system.
I suspect that if you give the water a swirling effect with your hand to create a whirlpool, it will drain properly. Do some searches on different types of vessel drain assemblies and check around to see which ones drain better.