# Stir plate question

Is it true that you can get the same amount of yeast in a smaller size starter using a stir plate?
Like a quart on a stir plate would equal 3 or 4 quarts not on a stir plate.

I’ve heard just what you said, in effect, a .5l starter on a stir plate will equal a 2l non stirred starter, but I’m a little doubtful. The pitch rate calculators I use generally show a 40-60% increase by using a stir plate versus not stirring at all, which is still a pretty meaningful increase. The other big advantage to a stir plate is the shorter time involved in producing a starter.

[quote=“Rookie L A”]Is it true that you can get the same amount of yeast in a smaller size starter using a stir plate?
Like a quart on a stir plate would equal 3 or 4 quarts not on a stir plate.[/quote]

In given amount of time, I think that would be true. But it seems like if you let the unstirred ferment out it would be equal. But I’m guessing…

I’m no expert either, but I gather when oxygen is plentiful yeasties focus more on reproduction. So I guess oxygen does for them what alcohol does for us… With less oxygen they convert sugar to alcohol.

So given that there is only so much sugar in the starter I’d believe the 40-60% increase over non-stirred, but not 3-4x. If you gave the non-stirred more time to ferment-out I’d bet you’d see more alcohol in the spent wort versus stirred. But again, just a shift in the balance, not night-and-day difference.

From personal experience with no numbers, I will say the same volume starters produced on my DIY stir plate have producer better big beers and been able to chew through my batches with much greater efficiency.

[quote=“Denny”][quote=“Rookie L A”]Is it true that you can get the same amount of yeast in a smaller size starter using a stir plate?
Like a quart on a stir plate would equal 3 or 4 quarts not on a stir plate.[/quote]

In given amount of time, I think that would be true. But it seems like if you let the unstirred ferment out it would be equal. But I’m guessing…[/quote]

Wouldn’t it be less because the stir plate also keeps the yeast from settling to the bottom so they should produce more (I think).

Could be, but I was thinking of the way I used to make non stir plate starters by giving it a swirl every time I went by. I didn’t do any cell counts, but it appeared there was as much yeast but it took longer to produce it.

Could be, but I was thinking of the way I used to make non stir plate starters by giving it a swirl every time I went by. I didn’t do any cell counts, but it appeared there was as much yeast but it took longer to produce it.[/quote]

That makes sense, that’s how I do starters now.
I’m trying to decide if I should direct some of my birthday money to a stir plate. Any particular ones that are better than the others?

[quote=“Rookie L A”]That makes sense, that’s how I do starters now.
I’m trying to decide if I should direct some of my birthday money to a stir plate. Any particular ones that are better than the others?[/quote]

I really don’t know. The only reason I have one is because someone gave it to me. It’s so old that all the markings have worn off.

This is the one I have, I got mine 1 or 2 years ago from the guy that makes them. I didn’t see anywhere to buy them on his website just links to stores that sell them.

http://www.homebrewing.org/The-Stirstar ... _1306.html

It comes with a lifetime warranty. The price seem close to what I paid, I can’t remember how much I paid but I didn’t pay much. I was going to build one but it wasn’t worth the hassle.

I suggest building your own stir plate. That way you can set it up to match your own needs. I often find myself using my stir plates for very small flasks when I am culturing wild yeast from a single colony or from bottle dregs that I have isolated a strain from. Each of my stir plates has multiple levels of variable speeds allowing me to have a wide range of options when it comes to very small to very large starters.

I will say, if money isn’t much of a concern, buy one; don’t build one. I spent many a frustrating afternoon trying to get a homemade stir plate to work for any extended period of time without the stirbar kicking out. Under perfect conditions I could get it to work for about an hour the i’d hear that annoying rattling noise. I got so frustrated I threw the damn thing in the trash and ordered the Vortex from here on NB. I think it’s like \$99.

Build it right and you will have no issues. There’s a bit more to it than just slapping together some HD magnets and a cheap computer fan if you want a nice stir plate.

I’m not very mechincally inclined and all the DIY plans I saw out there were hard drive magnets on PC fans. For some people it may be easy to “build it right” like you said but for me, I was baffled by it all. It was definitely worth spending a few more bucks on something that I knew would work.

I am also mechanically declined and wouldn’t even attempt to build anything more complicated then a double decker sandwich.

Don’t bother with hard drive magnets. They’re generally crescent shaped, and a pain to harvest intact. That makes for a plate that is much more likely to throw the bar. Home Depot and Lowes both sell the needed rare earth magnets for pretty cheap. They make the project a no-brainer.

Mine will occasionally throw the bar, but I usually take it as a sign that the speed was too high. You don’t need to send the yeast into ludicrous speed warp drive, just a surface dimple.

Because I didn’t have \$100 for a stir plate, I recently built one. In fact it’s getting its first use today! The big hang up for me was how to implement variable speed, which is a must have in my opinion. In my tests with plain water, if I maxed out the fan speed, the stir bar was always thrown. At 75% I get a nice vortex. Variable speed lets me ramp up to a perfect vortex. Anyway, recently I came across this post: http://lurkinggoatbeers.wordpress.com/2 … t-starter/ where he used a USB powered computer fan that has a variable speed controller built into it. So with the complication, and frankly risk, of implementing variable speed removed, the only thing I had to build was the enclosure and install the fan. I also elevated the magnet from the fan. Although I’ve seen some posts say it’s not necessary to keep the magnet away from the fan, the fan did run slower with the magnet right on top of it. So I raised the magnet away from the fan with plastic collars for a sink drain. It fit perfectly over the fan hub, which made it easy to glue. The magnet I got from an old computer hard drive. I made the centering of the magnet easier by gluing a thin piece of sheet metal to the top plastic collar. That way I could keep repositioning the magnet until I got it centered. Sorry this post is a little long. I just wanted to make the point that it might be easier than you think to build your own stir plate.

Keep in mind that the size of the vortex really doesn’t matter. Recent tests have shown that very little O2 gets drawn into your starter no matter how big the vortex. The main benefit of a stir plate is keeping the yeast in contact with the wort, not adding O2.

I prefer the speed control from stir starters.

it’s all bits you can get from Radio Shack.

While I know you have no plans of building your own, others who read this thread may want to.
This is my design and a pretty easy build. It provides two levels of variable speeds. Parts needed are a hobby box, 12v .30amp fan, 12v 500ma DC power supply, 25ohm rheostat, two rocker switches (one on/off, one on/off/on), LED, three 1 watt 10ohm metal oxide resistors, SS fender washer, and four neodymium button magnets. With one stack turned N and One stack turned S.
FAR less than the cost to buy a stir plate and more versatile than the traditional single stage variable speed stir plates.
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