REALLY GREAT ARTICLE !!! I was actually trying to find a post about cleaning glassware from a laboratory and was about to make a new post until I found this one ! Great post !
What is the best way to clean the inside of a flask?
If you don’t have a bottle brush, the best way to clean the inside of a flask is by creating friction by using rice, salt or bicarbonate of soda. As we shared in this article, you can pour rice into the flask and fill half of it with cold water. Close the flask then shake it for a few minutes. You can use the same process with salt and bicarbonate of soda.
Or
Bottle brush or a cleaning cloth with hot water
Or a round-bottom flask brush
Website on cleaning solutions of laboratory glassware