MoreBeer’s Fermentap Stir Plate along with a 3,000 mL Erlenmeyer Flask
This review is by Homebrew Finds Contributor Brad Probert. Brad is an engineer, expert homebrewer and experienced reviewer. Grab a link to Brad’s website at the end of this review.
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Fermentap Magnetic Stir Plate Y705
This is valid 5/30/24 only while supplies last
About Stir Plates and Erlenmeyer Flasks
Stir plates are pretty simple machines. There’s a small electric motor in a housing with a flat surface for you to set your vessel on that has wort needing to be stirred. When the motor spins, a magnetic field is created as a by-product of the electric motor. This is used together with a small plastic-coated magnet that looks like a small capsule, called a stir bar. If your flask is filled with wort, the stir bar spins around at the speed of the electric motor in the stir plate and creates turbulence in your wort. It creates a vortex like an underwater tornado as the spinning motion pulls wort down towards it and then flings it away when it contacts the stir bar.
This underwater tornado is the key to the stir plate’s success in preparing starters. This stir plate motion has two functions: 1) Keeping the yeast constantly in suspense and not letting them settle out, 2) The constant circulation of wort helps expose all of the wort to the surface where it can interact with incoming oxygen and purge CO2 developed by the yeast’s fermentation processes. There have been experiments done that show you can more than double the amount of yeast cell growth in a starter made with a stir plate versus a starter that doesn’t.
The vessel of choice for starters made on a stir plate is the Erlenmeyer flask (named after a German chemist who invented it in 1860). Its wide, flat base make it stable to sit on your brew table or on the stir plate without concerns of it getting bumped and tipping over. And very importantly, its flat bottom allows your stir bar to rest in the center and spin. A glass growler with its domed-in bottom, will not keep the magnet centered and then won’t work to stir the wort.
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Fermentap Magnetic Stir Plate – Magnetic Y705 via MoreBeer
When looking for Erlenmeyer flasks, you want to make sure you get one made with Borosilicate glass. It is less sensitive to growth/shrinkage with temperature extremes, meaning it can go through thermal shock with less risk of breaking. But there’s an important caution here. Borosilicate is not recommended for direct heating. I heard from a Customer Service Manager at a homebrew shop about the horrific pictures he got from someone that was carrying their boiling starter wort from stove to sink when the glass bottom broke and showered his [sandaled] foot with glass and 200 degree wort. So boil in a separate vessel before pouring into your flask, or let it sit and cool a bit before you move to the cooling stage.
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