I use this Corning PC-420D hotplate/stirrer kit* and would never go back to manual mixing. In fact, after having carefully watched liquids of differing densities being mixed in a beaker by this unit, I quickly came to realize just how poorly I had been doing it by hand. It takes more effort and quite a bit longer than one might think.

I also found it to be much more efficient to purchase and use an inexpensive kitchen hot plate and water bath to initially raise the temperature of bulk liquids to at or near the desired temperature, then transfer over to the Corning unit for temperature maintenance and stirring. It's a two-step process, but greatly speeds things up.

Ken

* I got it new, but didn't pay anywhere near that MSRP price!