How do I split and save a yeast starter?

The Short Version....
How do I split a stepped up yeast starter use half and save the other half? Besides counting with a microscope, how do I measure the amount of yeast in the halves? If I step up the stored half and split again, how many of these splits before I need a fresh vial/smack pack?

The long version...
I'm new to home brewing with a couple all grain batches finished. I'm moving from dry yeast to liquid. For the next year, I'll just be using the common popular California Ale yeast, so I can learn the different flavors of grains and hops. So multi-strain or long term storage isn't needed and I don't mind buying a new vial/smack pack every quarter. I'd like learn more about the yeast handling aspect of beer making, I don't have a LHBS, and saving some money per batch would be nice.

I'll be making a 4 or 7 gallon batch once or twice a month. So my thinking was I'd make a starter with 1L DME and the initial vial/smack. I'd let it sit on the stir plate for 24 hours, then in the fridge overnight. I'd decant it and step-up with ~1.5L DME and another 24 hrs on the stir plate and another night in the fridge. Which is what I did.

So, here I am now, I got my flask in one hand and sanitized canning jar in the other and I think, well I'll decant 80%, swish good, and poor half in canning jar. Then I'll do another 1L DME in the flask and stir plate again for 24hr. Then pitch that into this weekend's batch.

But..hmmm... how much yeast is in the flask now? How much in the flask after I split and stir up another 1L DME? The canning jar will go in the fridge to store... do I top off the yeast with sterile de-oxygenated distilled water or do I use sterile DME? For storage, how large or small of a jar/vial do I need?

My plan would be to repeat the process for my next batch in 2-4 weeks. If I do that, how long before the yeast is mutated enough to not be California Ale Yeast anymore? Can I do this for 6 months (6-12 cycles)?

*Edit*
Short story, make a big starter, cold crash, set aside half and use the other half for you beer (stepped up once more). The part you set aside, you can either split up into smaller amounts, or repeat the same process; make a big starter, use half for your beer and the other half for your fridge.

I'm a high gravity brewer, I like big beers, so I don't get a lot of "uses" out of my yeast.

At most, I brew three beers with one package of yeast; one low gravity beer (up to 1.060 with a starter) just to breed a lot of yeast, and two more >1.110 beers. I'll take the yeast slurry from the low gravity beer and use half on each subsequent high gravity beer.

Normally, I get one use out of my yeast; big starter pitched into a <1.110 beer. I could split my starter up after it's done, refrigerating one half (and also splitting that up) and then stepping up the other half, but I normally don't brew the same style of beer frequently enough to keep the same breed of liquid yeast on me at all times. I don't worry too much about dry yeast since it's cheap.

I dont have any scientific answers, but I do what you are talking about. I just go half and half. I make a starter, step it up, save half in a mason jar and pitch the other half on a beer. For the next brew, I make a starter and save half, and pitch half. And so on.

I plan on trying to learn a little more about cell counts and pitching rates but so far this has worked. There are exceptions of course, when I brew a Lager I make a HUGE starter and save only a little. The half and half thing is for normal gravity ales.

I don't worry about measurements either. I use 8 oz mason jars, and the day before brewing I fill them about halfway with water and put them in the microwave for a couple minutes til they boil. Carefully (with oven mits) put the caps on and tip upside down to sanitize. Then let them cool. When I go to pitch my starter I decant most of the liquid then dump in enough of what remains to fill the mason jar and the rest goes into my wort.

If you're going to be splitting on the same day you brew, I heard a tip on one of Jamil Z's radio shows the other day that would probably help you.

He was talking to a guy who was having trouble splitting a large start of a highly flocculant British yeast. He recommended decanting as well as you can, then adding a bit of cooled wort to your starter vessel, swirling and dividing the liquid equally. He said cooled unfermented wort almost immediately causes the yeast to go back into solution.

If you're using something with measuring marks on it, like a flask, add enough wort to get your volume to a number that can easily be divided in half. Swirl your yeast into solution and pour half of your flask into your beer. Put the flask back on your stir plate for 24 hrs so your yeast can finish out the new wort. Then chill, decant and store in your sanitized mason jar.

I routinely do what Dave and Craig do. IF the yeast is a little older (3 to 4 months) i'll step up twice before dividing. I usually don't cold crash the starter unless i'm stepping up again. I ALWAYS have the wort fermenting within 6 to 10 hours using this technique which tells me i'm pitching sufficient quantities of yeast. Don't fret about numbers. look at what your yeast is doing in the starter and gauge the "health" of the yeast from there. It should be at peak krausen in the starter in 12 to 18 hours. Often in the second step up you'll see krausen in 8 hours or less!
No matter what, any starter is yielding more yeast than a single smack pack or dry packet alone, and i'm sure you've made many wonderful beers using just a single packet of yeast, i know i have.

Thanks for the information.

Wyest has a picture on one of their pages where they estimate the amount of yeast cells in a plastic vial based upon it's depth. I've read estimates of the amount of yeast cells based on milliliter volume. Woodland Brewing talks about using a microscope, which is a bit too much cost and effort at the moment. I think I should get some smaller graduated containers or jars.

davekippen and craigT say Mason jars and I know I can get those easy and inexpensive at Walmart. I'll check if their marks are precise enough.

I think I'll probably want some graduated lab glassware, but it looks like it's mostly sold by case. For example, Wheaton Glass Volumetric Graduated Bottle with Phenolic Rubber Lined Screw Cap. Maybe a 50ml skirted centrifuge tube like on the Wyeast site. They seem cheap too like this Karter Scientific 208J2 Centrifuge Tubes, 50ml, 30x115mm, Blue Cap, Skirted, No-Leak (Pack of 50) . I read another thread where someone mentioned media bottles, but those are kind of pricey at about $15-$20 for a Pyrex single on Amazon.

Do you store the split portion in the fridge with water or wort?

Boiled and cooled water.

What are your thoughts on the method discussed in this HBT article discussing yeast harvesting from starter? Similar technique as being discussed above, but still somewhat different:

Yeast Harvesting: A Novel Approach?

Yes that article is what got me started wanting to do this, but it doesn't mention yeast cells count approximation. At the end though he's using a tape measure. With some premeasuring of my jar, I could probably do the same and know how many mL of yeast settled out and get an approximation of yeast cells. Do you think so?

This is an old post but wanted to see if my theory is correct.
I stepped up my starter using brewers friend.
I made a 6 liter starter which gave me 886 billion cells
This was made on a stir plate. When finished with everything still stirred up I
Poured 1 liter into a sanitized mason jar. This should be 1/6 of the total slurry
which should give me 148 billion cells.
This leaves 738 billion cells left, more than enough to pitch into my imperial stout.

I will only need halp of my WLP002 yeast for the oatmeal stout I am brewing and obviously want to save the other half. I just got a stir plate for Christmas and have never used liquid yeast before.

Is there any issue with pouring half of the yeast pack into the 1L starter and the other half into a glass vial I boil for 10-15mins and then soak in StarSan to store for a couple of months in the fridge?

I would do what SailorTodd recommended from this article: Yeast Harvesting: A Novel Approach? Put the whole thing in the starter. And you don't need to boil and star-san your glassware, just one or the other.

Today I'm starting a 2L starter, and I plan to cold crash it at high krausen, pour off most of the liquid, pour about 7mL yeast into a couple 15mL vials to freeze under glycerine. When the beer is done I'll probably wash the yeast and reuse it within a month, but if I don't get to it for a while I'll still have the little vials in the freezer that I can build up.
I read about it on the forums and pieced things together.
https://www.homebrewtalk.com/showthread.php?t=35891&highlight=glycerine