Overbuild yeast starter questions

[Bullhog]

At risk of being told to not worry so much, I do have a few of questions after trying an overbuild yeast starter yesterday.

If I’m making a 2L starter should I use a 5L flask? I didn’t use fermcap and there was a large mess to clean while on the stir plate.

If making a 1.8L starter, do I want to end up with 1.8L after boiling or do I want a smaller amount to account for the volume of liquid in the yeast packet, so final volume with yeast added is 1.8L?

I could just boil in the flask, but boil over seems inevitable, what do y’all do? Separate pot then add to the flask? I boiled in a seperate pot, but using a 5L flask and boiling in that seems more efficient.

Does fermcap keep the krausen down as well as prevent boil over?

Do you boil your stir plate bar with the wort?

For those interested here was my experience, you don’t have to read this. I was making a 1.8L starter with 100b overbuild. I measured out 1.8L water but at the last minute decided to add a bit more for boil off. I spilled a bit getting it into my flask after boiling, ended up with 1.5L of wort so I added a little more boiled water to make it 1.8L. I ended up with 2L after adding the yeast. This was all done in a 2L flash so the krausen went out of the flask. Now I have 1.5L. I’m just going to pitch that and forget about the 100b overbuild. I’m not worried about this round, but I’d like to have a better experience next time with more confidence in the process.

 

[wepeeler]

At risk of being told to not worry so much, I do have a few of questions after trying an overbuild yeast starter yesterday.

If I’m making a 2L starter should I use a 5L flask? I didn’t use fermcap and there was a large mess to clean while on the stir plate.

If making a 1.8L starter, do I want to end up with 1.8L after boiling or do I want a smaller amount to account for the volume of liquid in the yeast packet, so final volume with yeast added is 1.8L?

I could just boil in the flask, but boil over seems inevitable, what do y’all do? Separate pot then add to the flask? I boiled in a seperate pot, but using a 5L flask and boiling in that seems more efficient.

Does fermcap keep the krausen down as well as prevent boil over?

Do you boil your stir plate bar with the wort?

For those interested here was my experience, you don’t have to read this. I was making a 1.8L starter with 100b overbuild. I measured out 1.8L water but at the last minute decided to add a bit more for boil off. I spilled a bit getting it into my flask after boiling, ended up with 1.5L of wort so I added a little more boiled water to make it 1.8L. I ended up with 2L after adding the yeast. This was all done in a 2L flash so the krausen went out of the flask. Now I have 1.5L. I’m just going to pitch that and forget about the 100b overbuild. I’m not worried about this round, but I’d like to have a better experience next time with more confidence in the process.

First off, it's difficult to overbuild in a 2L flask. Just not enough starting volume. Typically you have to do step starters, which is a pain in the butt. If you use a yeast calculator like this https://www.brewunited.com/yeast_calculator.php it tells you starting volume based on your batch size, OG, overbuild and yeast age. Be aware it's a guesstimate, but without actually counting yeast cells it's the best you can do. It's worked for me for the last 7 years!

The good thing is you are actually making a starter. Although yeast count is very important it's more important to start with healthy, viable yeast vs more not-so-healthy yeast.

Fermcap helps with boiling on the stove and krausen formation (blowing out of flask). I used to use it when doing starters on the stove, but have since switched to bottled water and no boil. Boiling glass directly on the stove is a hazard if the glass cracks. Yet another fun thing to worry about when brewing!

Look into a 5L flask if you're planning on overbuilding/harvesting yeast. I emailed Omega directly and they told me 100ml can build up a 1L starter with no issues. So figure 200ml for 2L and so on. A 5L flask just means you can make larger starters for high gravity beer and/or harvest more.

I think you'd be fine using fermcap in a 2L flask with no more than 1800ml total volume, harvesting 300ml for future starters and pitching 1500ml directing into your beer. Of course, for OGs under 1.055-1.060 and yeast that isn't over 2-3 months old.

 

[Bullhog]

Well as luck would have it, my stirplate has died after the krausen overflowed.... time for a new fan...

 

[Deadalus]

At risk of being told to not worry so much, I do have a few of questions after trying an overbuild yeast starter yesterday.

If I’m making a 2L starter should I use a 5L flask? I didn’t use fermcap and there was a large mess to clean while on the stir plate.

If making a 1.8L starter, do I want to end up with 1.8L after boiling or do I want a smaller amount to account for the volume of liquid in the yeast packet, so final volume with yeast added is 1.8L?

I could just boil in the flask, but boil over seems inevitable, what do y’all do? Separate pot then add to the flask? I boiled in a seperate pot, but using a 5L flask and boiling in that seems more efficient.

Does fermcap keep the krausen down as well as prevent boil over?

Do you boil your stir plate bar with the wort?

For those interested here was my experience, you don’t have to read this. I was making a 1.8L starter with 100b overbuild. I measured out 1.8L water but at the last minute decided to add a bit more for boil off. I spilled a bit getting it into my flask after boiling, ended up with 1.5L of wort so I added a little more boiled water to make it 1.8L. I ended up with 2L after adding the yeast. This was all done in a 2L flash so the krausen went out of the flask. Now I have 1.5L. I’m just going to pitch that and forget about the 100b overbuild. I’m not worried about this round, but I’d like to have a better experience next time with more confidence in the process.

The yeast are going to eat the sugar. There's no need to vigorously boil the starter. In fact, a very low simmer is desirable from the perpsective of boilover. Not much of a big deal if you lose a little water to evaporation. If it bothers you, add 50 mls.

I use a pot. The flask is $20-$30 and will make a mess if it breaks. Plus that small area at top does little to prevent boilover. If you scorch the wort, that is harder to clean too. I would never consider boiling in a 5 liter flask, they are like $50! They do make 3 liters flasks, which are the perfect size for overbuilds but slightly more expensive and slightly harder to find.

Yes fermcap does both.

In the past, I usually did what wepeeler is suggests (but not boiling in the flask) as 1.8 l is a good volume to avoid krausen overflow most of the time. Fermcap, which I have but never considered, would be helpful. Then I would draw off about 300ml for storage. An alternative would be to make the 1.8 liter, pitch most of it, and save a small amount to build storage yeasts afterwards. This could be in the 500-1000 ml range. I've been doing that recently but I recently screwed up and forgot to save the small bit to do this on one yeast. Like I mentioned though, 3000 ml is a great size flask for overbuilding. On the other hand, I have done yeast calculations and often 2000 ml is overly conservative for low and medium gravity beers so taking some out is not a problem either using a stir plate at least.

I will note too that the initial starting numbers in my opinion are highly variable to begin with as far as the first yeast pack. You really have little idea how the yeast was handled prior to purchasing and then once you overbuild, that variability is again magnified. As one example, I think the calculation is that viability percentage reduces linearly and that is not at all a typical situation for organisms. Growth and mortality are very often exponential functions as a starting point which then get population bounds in closed environments. I have many times used yeast that should be dead by the linear reduction concept yet no problems with fermentations after the starter build.

 

[DuncB]

I weigh the flask with stir bar in, add about 100ml water and yeast nutrient. Then boil this on stove, reweigh at end to calculate boil off.
Malt extract is weighed into pan and then weight of water. Boil gently and then cool, reweigh and add to flask.
Checking my maths and accounting for volume of the yeast added as well.
I've had some yeast escape with 2000ml fill in a 3000ml flask. It is yeast dependent, never used ferm cap so no input there.