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Stir plate - throwing bar

Discussion in 'Homebrewing' started by yinzer, Nov 29, 2012.

  1. yinzer

    yinzer Savant (395) Pennsylvania Nov 24, 2006

    yep, another evergreen post.anyway

    I never has issues until I broke my 2000ml flask and got a new one. This one has a dome shaped bottom. The stir plate is a comp fan kit type.

    Are there flasks that just don't work? Like mine? Actually as I'm writing this I do see one stir bar manufacturing site the says a flat bottom works best.

    I'm looking at a bigger stir plate anyway. One for 5000ml. I'm looking at the "stir plate 3000". Or maybe the "black max". Anyone have one of these?
  2. I've successfully used a pickle jar on my homebuilt stir plate and that has a slightly concave bottom. I find if my stir bar is being thrown to turn down the speed of the stir plate; how fast you can run it also depends on starter size but YMMV
  3. Ones with a dimpled bottom are usually not good to use, Just need a flat surface for the stir bar to rotate. MY homemade stir plate started throwing my stir bar once I bought a 2000 ml flask. Working on building a new one, but I have had good turnout without a stir plate. Hope everything works out man, No experience with marketed stir plates
    yinzer likes this.
  4. jtmartino

    jtmartino Advocate (515) California Dec 11, 2010 Verified

    Slow it down.
  5. yinzer

    yinzer Savant (395) Pennsylvania Nov 24, 2006

    I start from a total stop. As soon as the fan moves on the lowest setting the bar is thrown. The more I Google it looks like the dimpled or curved bottoms just don't work well.

    I did play around some with just water and with enough pissing around I can get it to work. I'm going to wait until the yeast starts to work and not just clumped on the bottom. Maybe that will help for this batch.

    I'm going to get either the 3000 or black max.
    loony4lambic likes this.
  6. barfdiggs

    barfdiggs Savant (420) California Mar 22, 2011

    Go on Ebay and get a stir plate from a reputable scientific company. All of the homebrew stir plates are garbage compared to a good commercial one. Have no problem stirring 8 L of broth at work on 20 year old Thermo (IIRC) stir plate.
  7. jtmartino

    jtmartino Advocate (515) California Dec 11, 2010 Verified

    I've used many stir plates on many different containers (in the lab.) You're right - the problem is the shape of the bottom, and the only way to fix it is to increase the # of magnets on your fan or just get a new container.

    Or, you can try a real stir plate for $36:

  8. cracker

    cracker Savant (405) Pennsylvania May 2, 2004

    Mine gets thrown every now and then as well. I have to make sure that the stir magnet is first centered (use another magnet to do this) and start at a slow speed. My flask is not completely flat either.
  9. inchrisin

    inchrisin Savant (480) Indiana Sep 25, 2008

    Why stir broth?
  10. Patrick

    Patrick Initiate (0) Massachusetts Aug 13, 2007

    I would think an egg shaped stir bar might work better in the case of a non-flat flask.
  11. barfdiggs

    barfdiggs Savant (420) California Mar 22, 2011

    I use solid bacterial growth medium to make broth, but it requires some stirring before it goes into solution, and further stirring before it clears. If you autoclave some types of bacterial growth media (one type I use; overnight express auto-induction media that has several different carbon sources for expression of genes behind specific genetic elements) without dissolving first, it can scorch and change the chemical composition of the media, screwing up your protein expression work.
  12. thargrav

    thargrav Initiate (15) Nov 30, 2012

    This is Tom H of www.stir-plate.com. We designed & manufacture the SP-3000 and Black MAXX stir plates as well as the SP-2000 stir plates. While barfdiggs is correct - most good commercial stir plates are great products, the cheap commercial stir plates are junk. The stir plates we manufacture aren't near as good as one of the good commercial stir plates, but you don't pay $300+ for one of our products. Instead, we focus on delivering value for your money.

    This post did not start out being a plug for our products but I guess it turned out that way. If you get serious about one of our stir plates and stick with 2 liters I'd suggest the SP-3000 and not the Black MAXX. The Black MAXX is intended for up to 5 gallons and it's over-kill for a 2 liter flask. Black MAXX works great for 5 liters. Either stir plate will work with flat bottom or dome bottom flasks.
  13. yinzer

    yinzer Savant (395) Pennsylvania Nov 24, 2006

    Well until I get a real stir plate I'm going with this. Pretty high tech eh?

    I just shake and squeeze out the CO2. Actually I bet if I pumped sterile air in and just gave it a shake ever so often that I'd get great growth.

    Or maybe I could put a brick in the washing machine and hot wire it to stay on spin cycle.

    RobertColianni likes this.
  14. koopa

    koopa Champion (835) New Jersey Apr 20, 2008

    My stir plate 3000 works perfectly. I've used it for starters ranging from 1.5L to 3L so far and have nothing but positive things to say about it.
  15. VikeMan

    VikeMan Champion (855) Pennsylvania Jul 12, 2009 Verified

    I think you're better off doing what you're doing (releasing the CO2). Too much CO2 inhibits yeast activity.
  16. yinzer

    yinzer Savant (395) Pennsylvania Nov 24, 2006

    Yeah, I'll probably get one.

    I posted that kinda tongue-in-cheek, but for someone new to making starters or not wanting to shell out big bucks, I think that it's a simple solution. I've heard of people using 2-liter pop containers, so I wanted to do something like that.

    The only problem so far is that the top lid only utilizes about 120 degrees of a turn. Basically you can't it loosen it a lot and I need to have a finger holding it down when I shake it. I also wanted to squeeze it to suck in O2, but it doesn't like to reform properly. But as VikerMan says it's important for the yeast to have help releasing the CO2 and that's easily done. And it's working, I have 3 liters in it. No over foaming yet.

    Lastly I did use distilled water. I think that the DME will supply the needed nutrients/minerals, but I did add in some just to be sure. What's most important or might need to be added? Zinc and calcium?
  17. FATC1TY

    FATC1TY Moderator (895) Georgia Feb 12, 2012 Staff Member Verified

  18. jtmartino

    jtmartino Advocate (515) California Dec 11, 2010 Verified

    Yikes, my bad. Time to check eBay and craigslist! Forgot how expensive those little bastards are - around here you can get used lab equipment for pretty cheap (due to all the failed startups).

    I have access to stirrers, but I don't use one. I've never had a problem just swirling the flask.
  19. VikeMan

    VikeMan Champion (855) Pennsylvania Jul 12, 2009 Verified

    I don't doubt that a commercial stir plate would be better (longer lasting, probably), but I have used this one ($45) for a couple of years now, and it rocks for starters up to 2 liters...


    It never throws the bar, but my flasks are flat bottomed. I was kind of surprised to hear that there are erlenmyer flasks that aren't.
  20. koopa

    koopa Champion (835) New Jersey Apr 20, 2008

    I use the same unit for smaller starters and love it.
  21. FarmerTed

    FarmerTed Savant (345) Colorado May 31, 2011

    I use one of the cheapo fan-based stirrers with a 2L flask, and it works fine for me. When it starts to skip, or just make an inordinate amount of noise, I'll usually carefully reposition the flask until things are copacetic. It's not an Ikamag, but I think it's fine for the job. I personally would never purchase old lab equipment and then take it into my house or kitchen. I've worked with too many shitty chemists to even consider it.
    mountsnow1010 likes this.
  22. FATC1TY

    FATC1TY Moderator (895) Georgia Feb 12, 2012 Staff Member Verified

    Agreed.. some of the lab equipment I've used, I wouldn't dare even get it anywhere near something I'm gonna consume.
    kjyost likes this.
  23. beanboon

    beanboon Disciple (50) Florida Apr 18, 2011

    I find the sweet spot with speed and my rod stays put. My flask is a 2L with a flat bottom and I made my stir plate. If you made yours you may try using a stronger magnet.
  24. thargrav

    thargrav Initiate (15) Nov 30, 2012

    I believe you need to do this even on commercial stir plates - even the bottom of the flat flasks aren't perfectly flat.
  25. mountsnow1010

    mountsnow1010 Savant (370) Vermont Jan 23, 2009

    This is a crucial point.
  26. laikom

    laikom Aficionado (100) Illinois Mar 21, 2011

    I just want to 2nd the "add more magnets" suggestion. I had a personal problem with investing another $60+ for a flat bottom erlenmeyer flask (or even more $ for the size I wanted). I tweaked my homemade stir-plate, tried different size stir-bars, but the final thing that worked great was to add more magnets. It's so strong now that the magnet wouldn't budge off the domed part of my carboys if you tried shoving it. I can spin it fast enough to get the vortex to reach the stir bar of a 1 gallon jar. I think i used a total of 6 hard drive magnets three rows stacked 2 deep. I'm spinning my computer fan with 12 volts.
  27. pweis909

    pweis909 Champion (750) Wisconsin Aug 13, 2005 Verified

    Hey! Careful! Your giving shitty chemists a bad name!
    FarmerTed likes this.
  28. thargrav

    thargrav Initiate (15) Nov 30, 2012

    You are on the right track - I've taken a lot of home built stir plates apart and the most common mistake made is not using strong enough magnets. The next most common mistake is incorrect spacing for your stir bar. Your magnets should be spaced so that they hold the stir bar centered.

    With all three of our designs the neodynium magnets are sized right for the stir bar packed with the unit.

    Tom - www.stir-plate.com
  29. mclaughlindw4

    mclaughlindw4 Savant (250) Maine Jul 2, 2009

    For me it was the spacing, right number of magnets, and length of the stir bar. A shorter stir bar will be less likely to throw, it could be as simple as that.