I've recently purchased a stir plate and a 2L flask. I tested it out with water and the vortex was pretty weak. I threw just under 2 L of wort in there today, (with antifoam), and I don't see any vortex at all. I just see lots of bubbles. I'm totally new to this. How am I doing?
This has happened to me also. My homemade stir plate would do 2L of water but not 2L of wort, seems the fan motor is not strong enough to spin the bar in a thicker solution. If I reduce to ~1.5L I can get a vortex in wort. Recommend you decant about half of your wort and re-test. Maybe add until it starts to drag. I also found it critical to have the stir bar centered in the flask and directly over the fan motor before turning on.
Tilt the flask to one side to get the magnet to the bottom corner (you will be able to see it) then place the stir bar over the magnet with the flask still tilted. Slowly level out the flask and drag it to the center of the stir plate. The stir bar should stay attracted to the magnet. Start the stir plate slowly and increase the speed but not enough to throw off the magnet.
What I always do is tilt the flask so that the stir bar sits on the edge where the bottom curves up to the side. I then touch this to the middle of the stir plate so that the stir bar is directly over the fan. Then I set the flask flat and move it until it is centered on the stir plate. This way you can see the stir bar (on the edge) and ensure it is on the magnet. EDIT: or, what Oddnotion said.
