Tight Arse Stir Plate

[Jye]

Mine has a 500 ohm potentiometer in it, and it's still touchy as all hell. Actually, I think I put a 100 ohm resistor in parallel with it too, but still touchy. Usable though if you're careful. 500 ohm was the lowest I could find.

Check that its not a log pot which could be the cause of your sensitivity.

You may have a log pot which could explain why the control is sensitive, a linear pot should remove the sensitivity. To check look for an A (log) or B (linear) printed on the back of the pot somewhere.

 

[rwh]

Is that the normal practice or can you just dump the whole thing into the wort?

Well, it's a matter of opinion, and also the size of your stater. If you have a 3L starter brewed at 25C, is that going to add good flavours or bad flavours to your brew?

The choice seems to be pitching the whole thing at high krausen or cold pitch only the slurry after it's flocculated. I tend to do the latter because I'm too lazy to time it to high krausen, and there is very little additional lag introduced by doing it this way. See:

Cold Pitching Yeast

 

[rwh]

Check that its not a log pot which could be the cause of your sensitivity.

Nah, it's a linear 500 ohm, though adding the resistor in parallel destroys the linearity.

 

[barls]

couldnt get what i wanted so i ended up putting a couple in series and got what i wanted in the end so its now working fine

 

[domonsura]

Joined the stirplate club today (couldn't resist), made mine with a magnet ripped out of a computer HDD.

Test drive Saturday with Wyeast Bo Pils yeast that's been in the fridge for 4 months..............looking forward to much healthier lager ferments now....

 

[Sammus]

I re did mine recently with a 240VAC fan from jaycar and a ceiling fan speed controller (damn those those things are $$, not long ago I saw a pack of 5 go in ebay for the same price I paid for a single one :angry: - oh well, too late to return now).

It got a bit warm after running for 4 hours, so I drilled a few holes around the sides of the case and it doesn't have that problem anymore. The speed control is good, being a continuous adjustment one instead of a 3 point one. I only ever use it flat out at the moment, though I'm sure that'll change when I start making my starters from slants. Its much torquier fan than the computer one, definitely a good thing.

 

[Jye]

A heads up for anyone using one of these as a stir bar, I found one of mine had cracked. Im unsure if it happened while boiling it in water/wort or if it was dropped.

So just remember to check them before use.

 

[Sammus]

Hi, has anyone pitched their starter straight from the stir plate? I imagine their could be issues with oxidised wort - but I'm hoping ~1L of oxidised wort in 25L brew wont show itself too much because I just realised my yeast is on its stir plate still and I've already started my mash!

I'm thinking that the stirring drives off a lot of co2, so maybe theres like a constant upward draft of it and it doesnt get a chance to dissolve more oxygen after a while? has anyone actually pitched starter wort thats been on a stir plate to know the results?

Sam

 

[goatherder]

Do it all the time Sammus, mainly for ales though because the starters are only 1-2 litres. With lagers I tend to ferment them right out and decant off most of the liquid. I haven't noticed any oxidation problems with the beer. I assume the yeast is taking up the oxygen while it is growing.

 

[Gulf Brewery]

Hi, has anyone pitched their starter straight from the stir plate? I imagine their could be issues with oxidised wort - but I'm hoping ~1L of oxidised wort in 25L brew wont show itself

Sam

You should oxgenating your wort after pitching the yeast, they need oxygen to grow.

Cheers
Pedro

 

[Sammus]

Sam

You should oxgenating your wort after pitching the yeast, they need oxygen to grow.

Cheers
Pedro

I was thinking more of oxidation as opposed to dissolved oxygen - that is, what I understand happens if you dissolve oxygen in fermented beer.

 

[Gulf Brewery]

Sammus

The oxygen from when the wort is on the stir plate will be held within the wort - oxidation at time shouldn't be a problem.
If the wort was hotter, like mash temperatures, then the oxidation may be an issue.
Let's not start the war on HSA

Cheers
Pedro

 

[MVZOOM]

Team,

I'm about to take delivery of my stir plate. Here's what I intend to do to enact some good yeasty action:

- Mash some pale malt to obtain a few L of wort at around 1044.
- Sanitise some PET 800ml bottles and fill with aforementioned hot wort
- Freeze bottles, pending use for starters

When I need a starter, I'll then:

- pitch a VERY small amount ofyeast (say 2-3g of dried or 1/5 of a tube of liquid) to 100ml of wort
- Wack on the plate in a steralised container, with a glad wrap and a pin hole up top
- as it grows, add more wort to the existing flask, until I get full utilisation

Does this method look ok?

Cheers - Mike

 

[newguy]

You can never be too careful with a starter. If the starter gets contaminated, you're hooped. I'd recommend reboiling the wort after taking it out of the freezer, immediately before using it. I'd also recommend you put an aluminum foil cap on the top of your starter flask. Make it large, so that it overlaps the top of the flask quite a bit. Sanitise the foil and the outside of the flask near its top.

Someone else will have to chime in regarding incrementally feeding the starter.

 

[Sammus]

Also you didn't mention boiling the wort in the first place, you should probably do that if you weren't intending to. Personally I'd never store wort without pressure cooking it, but i think the debate has been done to death and bags not starting it again

edit: Also, According to studies I've read somewhere, they recommending stepping up in 5 to 10-fold steps.

I personally start from yeast stored under distilled water. I plate it, then after about a week pick a culture and drop it into 20ml of sterile wort. I'll usually give that a day or two to ferment out (probably happens in much less) then transfer to the stir plate in either 100ml (ale) or 200ml (lager) of sterile wort for a day. Then another step to 1L (ale) or 2L (lager). For wheats etc (haven't tried this yet but I plan to...) go from 20ml to 100ml to 500ml or something. That might even be too much if your looking for that stressed yeast flavour. time will tell!

FWIW, I also read that the greatest cell count in a step/starter is 12-18hrs after pitching - which i think is around high krausen, so this is a pretty good time to step up starters and pitch them also. Ensures maximum count and already active yeast.

 

[MVZOOM]

Umm, yes, sorry - I'd boil and re-boil the wort. Forgot to mention that. Why would an alu foil cap be better than glad wrap?? Also, any thoughts about incrimental wort additions?

Cheers - Mike

 

[Sammus]

Also, any thoughts about incrimental wort additions?

The pro's recommend going in steps, like my process outlined above.

 

[razz]

Umm, yes, sorry - I'd boil and re-boil the wort. Forgot to mention that. Why would an alu foil cap be better than glad wrap?? Also, any thoughts about incrimental wort additions?

Cheers - Mike

You can keep the aly cap on the flask while you're simmering the wort.

 

[MVZOOM]

The pro's recommend going in steps, like my process outlined above.

Sorry Sammus, actually missed your post! I guess there will be some trial and error with this stuff, will experiment and see.

Cheers - Mike

 

[johnno]

Anyone know anywhere in Melbourne city I can get a stir bar?

cheers
johnno