From a Russian document:
Лабораторная посуда считается чистой, если вода, стекающая по стенкам, не оставляет капель или «ручейков».
Laboratory glassware is considered clean when the water running down its walls doesn't leave drops or "rivulets".
But I'm not sure about "rivulets". What is meant in the original text are elongated, thread-like drops that would make the laboratory beaker hard to use, because these drops will make measurements imprecise.
I wonder what the natural-sounding English term would be for these.
From a website dedicated to titrations:
Laboratory glassware have to be perfectly clean before it can be used for any type of analytical work. There are two reasons for that. If the glass is not perfectly clean, water will not wet its surface, and it will be present on the glass surface in the form of droplets. It is impossible to account for volume of these droplets, so you will never know what volume of the reagent was used - and as the precision of the volume measurements is the basis of the precision of the volumetric methods, dirty volumetric glass means huge errors.