Stir plate question

[mosto]

So, I got around to building my stir plate (quite impressed with myself actually ). I ripped the guts out of a PC power supply, kept the fan and grabbed the magnet out of an old hard drive. I then cut a hole in the top of the empty power supply housing, secured the fan inside, glued the magnet on and wired to an old mobile charger. Flask and stir bar arrived yesterday so after testing the setup with 2L of water, grabbed the 2L of wort I had set aside and tipped a pack of Wyeast 1275 that I'd smacked a couple of days earlier.

My question is how long, generally, before I should expect some sign of activity. I realise the answer is probably, how long is a piece of string, but looking for a rough guide. The pack was manufactured 13/03/13, so has a bit of age on it, hence the starter. Also, while the starter is spinning along nicely, it is only a 5V adapter, so may be under-powered, but I figure as long as the liquid is noticeably moving, it's doing it's job. My previous method was the shake as you walk past method, and would take a couple of days before you noticed much happening. I assumed the stir plate would get things cranking within a few hours, but this morning, no signs of much happening. Just 2L of wort spinning around, no bubbles, no krausen. I was hoping to pitch this arvo before going camping for the long weekend.

 

[razz]

Hey Mosto. Generally speaking you would see plenty of activity in the first 12 hours but as you said, the pack is an old one. I've no doubt it will get there eventually but you need to look for a few indicators that will tell you things are happening. It obviously stirred overnight so if it did ferment out you may see some moisture (respiration) forming inside the flask or a fine ring of sediment just above the fluid level. Also as the yeast grows the stir bar can visibly slow down from increased sediment. You could try leaving it turned off for an hour and see how much sediment settles out in the flask. You're right about the speed, as long is the starter is visibly moving then that is enough to get things going.

 

[Scooby Tha Newbie]

This is my third step up. I've built it off a London ale (1028) New packet. This is my first brew with it.

View attachment 68247

I plan to get 6 starters from the one packet. I treat these as mini ferments(beers).I will clean the "beer" once full ferment has been reached,about four days. At this stage I will split into 5 starters.

 

[wbosher]

I have read that sometimes you can't actually see any action at all. Until you turn it off after about 24 hours and there is more yeast than you started with.

No actual experience here, just something I read...

 

[Scooby Tha Newbie]

Yep true mate.



I came home today to find yeast had settled at 500 rpm. I ramped it up to 1500 rpm and it became soluble again. But you need to be carefull or you can knock out all the CO2 and get a volcano. The old girl will not like that.

 

[mosto]

Came home from camping today and it was done. A 'milky' look to it suggesting that there were lots of new yeasties ready to do their thing. Also a ring an inch or so up the flask where the krausen had been. Put my cube of English Bitter in the fermenter and dumped in the starter. Four hours later, solid krausen had formed. Never had a batch kick off so quickly.

 

[Yeastfridge]

I regularly don't see any krausen on my stir plate starters, I think the mixing stops a proper krausen from forming. You should have much more yeast in the bottom once you turn it off and let it settle as wbosher said, otherwise my airlocks are usually bubbling away like mad after within ah hour after pitching an active starter.

 

[Yob]

I pretty much always get krausen, sometimes it even climbs out the flask, 'could' be be yeast dependant I guess.. Even starting to think I need foam control.

 

[dicko]

Some lager yeasts don't form much of a krausen in the flask however as above, you will notice that a lot of yeast has settled and slowed the stir bar over the first 12 to 24 hour period from some varieties of lager yeasts.

1275 usually throws a head of krausen then settles out generally within 24 hours.