StarterRX

Last revised: 10-Feb-08

Or how to fix a broken starter...

I intend to demystify your relationship with your sourdough starter.  Unlike many other informational sourdough aficionado sites (and there are many-- some very good!), you'll find a definite lack of the huffing and puffing, and intentional, self-important, minutia laden obfuscation that you can find pervading so many of those sites.

Using sourdough is all really pretty simple and straight forward--once the veil of mystery has been pierced.  There are no mysteries on this page--just the opposite: information.  It's important that you learn how to identify a vibrant, healthy starter.  You need to know what that state looks like, so you can know when it's sick or needs refreshing.  Once the state is established, if needed, you can "fix" it.  Just follow the directions below, and you'll do just fine.  If you need a more thorough understanding and/or more technical details, you'll find them nearer the end of this page.  If your starter is okay, and you just want to save some of it, go here.

Be advised that there's a quantum difference between knowledge and wisdom.  If you're like me, you don't really want to wade through reams of tedious information looking for the few golden nuggets of knowledge while your starter is slowly going belly up.  I will impart to you all of the knowledge that I've prised from the volumes of repetitive and often contradictory tomes--so that you, gentle reader, might not suffer the same travails.  However, it will still be up to each of you to practice turning that knowledge into wisdom.

Okay?  Then let's get started.  No matter where you get it or how you care for it, at any given point in time your starter will fall into one of these three states:

  1. Healthy and Alive (normal),
  2. Barely Hanging-on (sick) or, 
  3. Looks Dead (flat).  

For anything else you don't need a doctor, you need an undertaker; or in ER parlance, it's "circling the drain!"

How to Fix:

I've streamlined and simplified the "new" and "refresh" procedure into a single, simple, consistent, sequence of events.  Something simple enough that even I can follow it!  If you have starter and it's quite new or you're not sure if it's working as it should, jump to Refresh.  If you've got some crumbs of dried starter and you are trying to get it going, continue at New.

New:

If you have purchased a starter, use the instructions included with it.  Or, since so many of those vendors get all ate up with themselves, you can follow my method instead--your call!  If you've received or have kept a dried specimen, then do this:

Mix the dried starter crumbs and 1-tablespoon of flour into a 1/2-cup of water.  Let stand for a half-hour or so.  Continue, and use in place of the "1-cup of your starter" below.

Refresh:

  1. Mix 1-cup of your starter into 1-cup of water and 1-1/2 cups of flour.
  2. Proof at [ 85F ] for 12 hours (see note about temp).
  3. Look at your starter.  Unless it was overheated and killed, it should be "flat", "sick", or "healthy."  If it's healthy, go to, Done (below).
  4. If not yet healthy: few bubbles, early hooch, gelatinous consistency, no froth on top, or any two or more of these symptoms; put the starter into the refrigerator for 12-hours.
  5. Remove from refrigerator and go back to step #1.  

Repeat the preceding sequence until your starter is healthy.  Although as many as 4 or 5 cycles may be necessary for extremely abused starters, most become healthy and active starters in 2 or at most 3 cycles.  If after 5 cycles of doing this you still get no bubbles or activity, your starter is beyond help--it's stone, cold, dead!  You'll need to start over with a new culture inoculation.

Alternatively, if, after a week of slavishly following these instructions, you finally "do" begin to see a few bubbles and it seems that you've resurrected it, it's almost certain that you've managed to capture and promulgate a purely incidental "wild" yeast.  Although fun and interesting; I don't recommend that you use it.  The chances that you'll have come upon an heretofore unknown new strain of sourdough culture is near nil.  I suggest that you toss your brew and go out and buy (or beg) a bit of starter from someone that has a working culture.

TEMPERATURE REQUIREMENTS:  The 85F temperature has been selected to ensure and promote the growth of lactobacilli--the lack of which is the most common cause of a poorly performing culture.  LB's do better warmer than cooler, so we use this value to make your starter healthy.  It is also the upper optimum temperature for a healthy yeast component.  Once your culture is vibrant and healthy, you can execute the refresh cycle using ordinary room temperature ~68-75F or so...  Click here for more details.

An important and oft missed step is to check your starter often, so you can begin to recognize, by sight, what state it's in.  At it's height of yeast activity (in the 8-18 hour range) it should be bubbly, foamy, and look and smell active (that's the best time to use it).  You need to learn the characteristics of your starter.  So invest some time with your eyes open...

Done:

Congratulations!  You did it!  You've successfully grown a healthy, working, sourdough starter culture.  This is called your "mother culture".  Everything you make, you'll make from this starter.  Feed it a few tablespoons of flour and water, and put it into the refrigerator.  You'll find that this culture is pretty robust and tough.  It can survive a lot of abuse.  But remember, ONLY flour and water ever go into this culture!  If you want to experiment with anything else, remove some of it to another container and experiment on it there.  NEVER contaminate your mother culture with any other adulterants!

Maintenance mode:

Once healthy, keep your culture in the refrigerator, replace anything you take out to use with about an equal weight of 50:50 flour and water.  If you don't use any, then give it at least a tablespoon or so of flour and water about once-a-week or so.  If you do this often without using any, pour some off, or make pancakes with the excess batter...

Caring for Your Starter:

You should keep your starter in a covered, non-metallic container.  Keep it refrigerated between uses, remembering to feed it by replacing what you use in a 50-50 mix (by weight) of flour and water.  If you don't use it, add a tablespoon of water and one of flour at least once a week or so.  Just to reiterate, the ratio of flour to water is not carved into stone with the instant demise of your starter if you screw it up.  But in my experience, I've found that a 50:50 mix, by WEIGHT for flour and water is about right.  That will give you a 100% hydration starter culture.  In volumetric terms, that would be about 1-cup flour and 3/4-cup water.  Scale it that way up or down as needed.

Every few months or so, you might want to trot it out and go through the refresh procedure as defined above.  But, if it's working okay for you, then it's really your call.

Look, these critters are pretty easy to keep happy and alive.  I usually feed 'em once a week or so...but I've let 'em slip to the back of the fridge and didn't find 'em again for the better part of a year!  But, a couple of days in a "refresh cycle", and they were right back to their full glory.  If you keep 'em in a cellar or other non-refrigerated place, you might have to feed 'em a bit more often than once a week. 

Caring for your critters isn't all that much different then caring for a goldfish.  Just feed 'em a little on a regular basis and they'll happily hang around forever...  Just one point of caution: the warmer you keep them, the faster they eat and multiply!  This isn't bad...it's just that if you don't feed 'em they'll starve.  Fortunately they don't all die at once.

If any liquid, called "Hooch", forms on top, stir it in before you use the culture.  The liquid contains lots of stuff, all of it is a part of the culture.  Just because it's separated doesn't mean it's bad; it's a normal occurrence.

Every 3-6 months or so, I start a new culture container with 1-cup of fresh flour and water; and pour in 1/4 cup or so of well stirred critters.  Let 'em sit at room temp for a few hours, and then put 'em back into storage.  Wash the old container to have it ready for the next usage.


Healthy and Alive (normal):

When freshly fed, a normal healthy starter has a smooth, satiny pancake batter like consistency.  It is shot-through with tiny bubbles above and below the surface.  It typically has a layer of frothy foam covering most of the proofed starter.  The froth can appear as early as 8 hours into the proofing period and can last 18-20 hours or more into the proofing cycle.  There must be *NO* hooch (a grayish-yellowish liquid that forms in older starters) visible.

Stirring the starter obviously releases a lot of gas (smells good).  Examining the starter clinging to a spoon should show a starter packed full of little bubbles.  Keep in mind that a foamy starter often appears all puffed up when the proof is done.  It will reduce in volume as you stir it and release the trapped bubbles.  As a final check, healthy starter should be able to raise plain white bread dough in 2 1/2 hours or less.  It's probably not worth the time to experiment with dough raising until all of the above characteristics of being a healthy starter are met.  Congratulations!  If your starter is like this, you can pronounce it fresh, vibrant, and healthy!  It's ready for bread recipes, will be much more resilient to abuse and mishandling, and should be very reliable for months to come...

Rising times of fresh, healthy starter in bread recipes of 2 1/2 hours or less should be expected.  Healthy, it is very abuse resistant.  You can now get by with less accurate temperature control during proofing, water content of the starter, and less careful control of the actual proofing period (although that's not recommended).  The only real way to mess up a healthy starter is starve it (not feed it for a long time), or heat it up to an excessive temperature (greater than 100F) for too long.  Nearly everything else will be ok, and even if you seem to have killed it off somewhat, one or two well controlled refresh cycles should bring it back to life.  You can get away with feeding it only once very two weeks or so too (but feeding it weekly is better).


Barely Hanging-on (sick):

Visible bubbles exist, but there is no frothy layer of bubbles on the surface of the starter, and bubbles beneath the surface are not plentiful.  It's likely that a layer of hooch (a benign grayish or yellowish, mostly clear, layer of water and alcohol) has formed on top of or somewhere in the starter even though it was not proofed for more than 12 hours.  Stirring the starter with a spoon, then drawing the spoon out of the starter and examining the starter clinging to the back of the spoon shows only a few bubbles in the starter.  Note that one of the key symptoms of starter in this stage is the layer of hooch which mysteriously appears "early," (vibrant, fresh starter usually requires 24 to 48 hours of proofing before any hooch appears.  

Other symptoms of this stage include slow rise times ( 3-6 or more hours to raise a bread recipe to double (if it ever does double).  Second risings are quite often unsuccessful and the dough appears 'dead'.  The dough may have a dead feel to it and tend to flatten out by itself while rising, even though you kneaded in enough flour and the gluten was well formed.  The starter itself may also have a gelatinous feel to it, rather than maintaining a smoother, pancake-batter-like consistency.  Starter in this stage has not stabilized the symbiotic relationship among the microorganisms present, i.e. the ratio of yeast and the various lactobacilli has not stabilized and the starter is not ready to use (except for pancakes).


Looks Dead (flat):

No visible bubbles, but you believe you have done nothing that should have killed the yeast, i.e. the starter has not been subjected to temperatures in excess of 100 degrees Fahrenheit or so.  It's possible that you neglected to feed the starter for so long that it appears that all life has gone out of it.  Quite often, starter in this stage is quite sour.  And equally as often, starter in this stage may be very mild.  The starter may have lactobacilli growing in it (sour smell) but the yeast has not taken off yet, or nothing at all is growing in the flour/water mixture yet.


What is Sourdough?

Sourdough is a symbiotic mix of micro-flora (yeast) and micro-fauna (lactobacillus) whose life-needs complement each other.  They occur in a ratio of approximately 1:100.  A wide variety of combinations of the families of these two groups of organisms occur naturally in flour.  A relatively select group of each can successfully live in a symbiotic relationship with the other.  The yeasts digest and breakdown the complex carbohydrates in the flour, and the lactobacilli eat that and excrete a mildly acidic mixture that serves to kill other yeasts and bacteria.

Many different yeasts can live successfully with many different lactobacilli.  Some combinations may taste great--and become what we know of as "San Francisco" sourdough.  Other combinations become known by other names.  Some don't do some things well (don't rise), others do them too well (rise too much or too fast).  Some may well taste great, others may be very foul.  It's this broad spectrum of possibilities that attracts the "wild" sourdough culture hunter--but that's a subject for another missive.

Like all communities, a sourdough culture grows in cycles.  In a new culture the yeast, tiny fungal plants able to consume plain flour, is first to begin massive multiplication.  They alone can digest the flour, and are needed to produce the lactose and other products that the lactobacilli use as food.  As long as they are moist, have access to fresh flour, and are kept relatively comfortable (68-85F) they will exponentially multiply until they exhaust their food supply or begin to suffer from the effects of their own excretions.  They consume flour, produce CO2 gas (the bubbles--which cause the "rise" in the bread), various lactose products, and some alcohol (yippee!).  The alcohol they generate will negatively impact both themselves and any bacteria that can't survive in that kind of environment.

As the yeast peaks and achieves majority, it will have eaten most of its flour food and begin to go into numeric decline; and the alcohol tolerant lactobacilli will begin to bloom.  These are the guys that make the acids (the reason you shouldn't store the culture in metallic containers) that give the sourdough its unique flavors.  The acids also kill any "foreign" organisms (yeasts and bacteria) that might find their way into your culture clan.  As the lactobacilli food (lactose, some flour components, and dead yeast cells) is consumed, they too go into decline, and the culture will reach stasis.  Although many of the organisms will have died, there are always some that survive--since it is not possible for every critter to eat every bit of food exactly gone.

When both the yeast and lactobacilli begin to be impacted by their own by-products, they go into suspension.  That's where they simply exist without reproducing.  Eventually the culture goes dormant, as the food is consumed and no more is made available.  Over time, a dormant culture, left unfed, will die.

You want to use your culture for baking when the yeast is at its peak.  This will produce the fastest rise, and will quickly permit the lactobacilli to begin the "souring" of the dough.  You want to save (dry) your culture when it's gone dormant--about 48 hours at room temperatures after last having been fed.

Once vibrant and healthy, the culture can be stored for months in the refrigerator and reconstituted as needed.  However, Darwin's laws work even in your culture container deep in the cold, dark recesses of your refrigerator.  Leave it too long, unfed, and cold; and new, altered, generations will begin to populate your culture.  The wise sourdough baker feeds his refrigerated culture at least once per week.  If the container gets more than about 1/2 or 3/4 full, discard some--or use it to make pancakes or waffles.


Purpose of sourdough:

The purpose of the sourdough culture is several-fold.  First off, the yeasts digest the raw flour granules and generate several end products.  They generate carbon dioxide gas that gets trapped within the gluten fibrils and causes the bread to rise.  In addition they convert some of the starches to sugars and some of those sugars to alcohol.  The lacto-bacteria convert some of the sugars into the acids that make give sourdough it's "sour" taste.  While they can and do more, those two functions are their primary purposes and the reason we use them.

There is also an interesting side benefit/purpose.  Many of my fellow Americans have finally come to the realization that they've been lied to by the medical/nutritional establishment for many years.  The greatest impact on our citizenry is obesity.  And for those many years, we were taught that FATS & OILS were the evil killers in our diets.  This is completely, 100%, totally WRONG!  Contrary to what so many folks think they "know", the ONLY thing that can be stored in a human 'fat cell', are molecules of glucose (under the control and direction of molecules of insulin)--NOT fat (from dietary fats & oils)!  And the ONLY external source of glucose is from dietary carbohydrates--from plants.  The worst glucose sources are: potatoes, pasta, direct sugars (honey, corn syrup, etc.), grains (rice, oats, wheat, any kind of grain), and to a lesser degree all other plants (fruits & vegetables).  There are a few exceptions, but those are minor.  The good news?  The digestive action of the sourdough critters dramatically reduces the carbohydrate count of bread!  So, sourdough bread is not only good tasting, it's a good deal healthier than "regular" bread.
[NB: A much longer, more detailed description of the dangers of a high-carbohydrate diet will be forthcoming...soon...]


Ingredients:

A true sourdough starter contains ONLY the following ingredients:  flour, water, and culture.  NOTHING ELSE!  Salt is included here only as a reference for the dough--it's NEVER used in the starter!

Flour:

Any kind of flour will do, although different types of flour can yield somewhat different culture results.  Rye flour will make your culture wonderfully sour, with my only comment being that pancakes, waffles, or cinnamon rolls made with it probably won't please the majority of palettes eating it.  Cake flour will leave your culture thinner and weak (leaving it pretty well unsuited for bread baking).  Consequently I use the same flour that I generally bake with, in my culture:  plain, ordinary, unbleached, white AP (All Purpose) flour, or "bread flour" if need be.  Shoot for 10-11% or so protein content.  Even if I make rye or other breads, I always only use plain AP for my culture.  Keeps things consistent, and being relatively neutral makes it a snap to integrate into different recipes.  If you must use another flour, simply substitute your flour of choice in place of the AP (or bread flour if you're using it).  NB: The kind and protein "value" of flour is somewhat regionally varied.  In the south, where lots of biscuits are made, their flour is much lower in proteins.  So beware...

Water:

You're going to need good, clean, water.  Most tap water is okay.  But, "city water" is usually chlorinated.  This is done to kill "little things" growing/living in the water.  That means it'll kill our SD critters as well!   If you must use it, leave it out for a day or so and the chlorine will evaporate.  If you live in one of the more "advanced" metropolises, they probably use chloramines, and them suckers DON'T evaporate!  Since I don't have a well or a natural spring, I use bottled water--you can use whatever floats your boat.  If you end up killing your culture, this is a likely place to start looking.

Salt:

Although not used in the making of your sourdough culture, the definition of the appropriate salt has been included here for completeness.  Ordinary "table salt", as sold in most of the world today has Iodine, a trace nutrient, added.  The problem is that iodine is a powerful anti-microbial.  Although many use it with no problems, I recommend against it.  I use Kosher or Sea salt.  Kosher salt is completely iodine free, and the trace amounts in sea salt are not a problem.

Sourdough Culture:

Although it is possible, you can't reasonably expect to "grow" a valid, working, useful sourdough culture off of a grape, out of the air, or by fooling with yeast, yogurt, or boiled potatoes.  If somebody wants you to use yeast or some other pseudo-sourdough--run away!  

No matter what you might read or hear from legions of "experts", you CAN NOT "create" a specific, viable, defined culture by capturing wild yeasts "out of the air".  The yeasts and bacteria that comprise a valid, active culture are a team that selects itself out of a nearly infinite combination of permutations possible from the "wild".  Partly this happens because they're already there, in the flour--they're a natural component of it; and partly it's by happenstance--you know, "stuff" happens!  

You can not select or build the right combinations using milk, sugar, grapes, potatoes, grain, or any of the other hair-brained schemes often found in so many publications.  If you want to make true sourdough bread and don't know someone who will give you a bit of their culture to start the process, spend some of your "bread" and buy one!  There are literally hundreds available on the web.  Trying to hatch your own can be both a challenge and a thrill--and I'm not against such efforts, but it's not a task for a newbie sourdough baker that needs and wants palatable results.  The odds are far, far more likely that you'll get something that is tasteless at best, or foul and possibly dangerous at worst.  If nothing else, you'll spend much of your time and energy trying to make bread that doesn't rise, or if it rises, doesn't taste good; and get disgusted with the whole process.  If you're new at this hobby, go out and buy a valid, registered sourdough starter from a reputable supplier.

There are many, many different culture formulations.  Over time and experience some of those have evolved to become what we know as "San Francisco" sourdough and other specifically named (typically regionally) cultures.  Each is a slightly different mix of critters that have, over time, evolved to work together in a manner that pleases the baker.  Also, as cultures age they change--Darwin's theories at work.  So, if you happen upon a working, tasty culture; just keep doing whatever you've been doing.  You might also want to consider taking a bit of it and preserving it, by drying it--in case you inadvertently cause yours to expire...(trust me, BTDT!)

Container:

You'll need to obtain a clean non-metallic container for your long term starter storage needs.  I use an old-fashioned glass, wide-mouth, snap-lid, jar with a rubber seal-ring.  But any old non-metallic container will do; ceramic, glass, even plastic is fine (just harder to keep clean).  Be certain that the contact surfaces (the part that contacts the culture) are non-metallic.  Being wide-mouthed and easy-to-clean is a plus!

Tools and materials:

Every once in a while you're going to read blistering diatribes from some of the "purist" adherents to the sourdough culture and how to work it.  One of the entreaties you'll probably most often hear is, "ONLY AND ALWAYS USE WOODEN TOOLS AND GLASS, CERAMIC, OR PLASTIC BOWLS!"  Okay, as an accomplished amateur biologist I have a fine, working, laboratory quality microscope.  I am very well versed in how to use it--and do so fairly often.  I looked.  Trust me, the "critters" have no eyes!  They can't tell what you're using.  While I most often use wooden spoons and tools, I use what makes the most sense at the time.  The dough can dry-on and stick very tenaciously as you work.  A metal spoon works far better than a wooden spoon for scrapping those crumbs and flecks off the bowl.  I use a metal whisk for mixing, and have used metal bowls as well.  So don't lose any sleep over not having the exactly "right" kinds of tools or bowls.

For certain, the yeast beasties are pretty well inert and not bothersome to, or effected by, metal objects--other than extreme temperature variations could be infused (a very hot or cold utensil and damage a small contact portion of your culture).  However, it is possible--however unlikely--that given enough time, some of the acid created by some species of lactobacillus could eat into metal.  While I've not gone so far as to do a detailed titrimetric analysis, the acid generated by the lactobacillus is going to be far too weak to have any measurable effect on any metal utensils used while baking.

That having been said, it's only for the long term storage of your culture that I don't recommend metal contact.  Feel free to use metal tools and so on, even metal bowls for working the dough.  But you should avoid permitting metal contact when storing your culture for the long term.  It is possible, however unlikely, that some metal may be absorbed by your culture over long periods of time.  While almost surely not a health problem to the typical human organism, it is possible for your culture to become discolored, develop an objectionable taste, or even be killed by micro-metal poisoning.

Drying your starter:

It's probably a good step to dry samples of your starter in order to preserve it against a catastrophic calamity, or for sharing with family and friends.

One caveat on drying; the yeast component of your culture will dry well.  Yeast will form a protective covering (sporulation or encystment), and can ride out the drying cycle for centuries.  However, the lactobacilli don't fare as well.  While some can ride out a dry cycle, others can't.  This is why a dried starter sample may take several refreshing cycles.  If none survived, it's almost certain that new ones will be found in the flour--which is after all, where they live and came from in the first place.

You should capture a sample just before you decide to refresh your entire culture.  Take your starter out of the refrigerator and let it come up to room temperature for at least 24-hours or so before you take your sample for drying.  Once you've extracted your sample, refresh the culture in the normal way starting from step #1 above.

Spread out some waxed paper.  Stir your culture well, and using the stirring spoon, transfer some of the culture onto the waxed paper.  Use the back of the spoon to spread it around.  Thinner is better than thick, slow-to-dry sections.  The wet culture should be protected and kept clean.  I allow mine to dry in a cold oven.

Once dry, all you need to do is bend the paper a bit and the dry culture will pop right off.  Bag it, label it (including date), and put it in the freezer.  From time-to-time you might want to take some out and test it by refreshing it.  Just to make sure that you did indeed succeed in capturing a viable specimen.

Monitoring the Refresh Temperature:

This important issue seems to be a mysterious art with most folks.  I usually "brood" my culture in the oven, OFF, but with the "oven light" on.  In my oven, at most times of the year, this seems to work out pretty well.  But it is sometimes difficult to tell how "close" the actual temperature is.  Early in the morning, in a cool kitchen, the culture "seems" to be too warm.  Later in the day, against the backdrop of a warm kitchen, the culture "seems" to be too cool.  It is difficult to accurately determine the temperature only by touch.

Our target temperature is: 85F.  Most oven thermometers don't go that low, most refrigerator-freezer thermometers don't go that high.  What's a sourdough aficionado to do?  Simple:  Purchase an inexpensive 4-6 inch round-dial thermometer designed for outdoor use--about $5 bux.  Ditch the mounting hardware, and simply stand or lay it in place.  The large easy-to-read black numbers against the white dial and the big red pointer are visible from across the kitchen.  Makes keeping casual track of my culture temperature, a snap!

I set it against my digital home thermometer system to see how close it was.  Turns out it was spot-on.  If it's off, say it shows 72F when it's actually 70F; if it has an adjustment, make it.  Otherwise simply add or subtract the error from the readings.  Absolute digital accuracy isn't necessary--within a several degrees is just fine.

One final word on temperature; according to the most recent studies, 86F is the ideal "average" between the best temperature for yeast and the lactobacillus.  I promote and use 85F because it's an easier number to remember, and it gives just a bit of bias towards the yeast.


Technical Details:

If you're a techno-geek or glutton for punishment, here's some more data.

The growth of Lactobacillus sanfranciscensis and Candida milleri (the two main components of your "typical" San Francisco sourdough culture), can be summarized as follows:

If refreshments are constantly above 32C (90F), the yeasts will eventually drop out. 
If refreshments are constantly below 13C (55F) the lactobacillus will eventually drop out.
Translation: if you keep it between 65 - 80 (pretty well room temp in most of the world) you'll be just fine.  All of the pundits and their titanium devices with digital accuracy be damned!

Time:

The generation time (time for the culture to double) of L. sanfranciscensis in rye dough at 28C (about 82F) is just under an hour.  This figure will vary with both temperature, and different strains of flour--although the differences from flour appear to be minimal.  If the inoculant size is reduced from 20% to 2.5%, itll take about three hours longer until the dough is "ripe".  

Absent a better definition of ripe, I use; a cup = 16 tablespoons.  Therefore, in one hour, at 82F, a tablespoon of starter doubles to 2; in 2-hours, to 4; in 3-hours to 8; and in 4-hours to 16 tablespoons--converting the entire cup.

PH:

The optimum pH for lactobacilli is 5.0 - 5.5 (which is the initial pH of a sourdough with 5 - 20% inoculum), the minimum pH for growth is 3.8 (they usually produce acid until pH 3.6 is reached).


The temp/working chart from Darryl Greenwood's fine sourdough website.

Color legend, best:  YEAST temp, LB temp, COMBINED REFRESH temp.

Temp F

LB. sf I

LB. sf II

Yeast-C. milleri

Avg.

36 0.019 0.016 0.004 0.01
39 0.026 0.022 0.008 0.02
43 0.035 0.031 0.013 0.03
46 0.047 0.043 0.021 0.04
50 0.063 0.06 0.033 0.05
54 0.084 0.08 0.052 0.07
57 0.11 0.11 0.078 0.10
61 0.14 0.15 0.11 0.13
64 0.19 0.2 0.16 0.18
68 0.24 0.26 0.23 0.24
72 0.3 0.29 0.3 0.30
75 0.37 0.37 0.37 0.37
79 0.45 0.46 0.42 0.44
82 0.49 0.55 0.42 0.49
86 0.61 0.64 0.35 0.53
90 0.66 0.7 0.2 0.52
93 0.66 0.7 0.05 0.47
97 0.58 0.54 0 0.37
100 0.39 0.31 0 0.23
104 0.1 0.055 0 0.05
106 0 0 0 0.00
NB:  0.7/hr ~ doubles in about an hour at ~82F
4 Tbsp = 1/4 cup; 16 = 1 cup

Hrs: 

1 2 3 4 5 [ 85F ]

1 Tbsp: 

2 4 8 16 32

Best yeast temp: 

81 F        

Best LB temp:

91 F        
Best combined temp: 86 F        

Credits:

As with most things, this page is an amalgamation and summary of the works of many others before me.  Among them; Darryl Greenwood.  Thank you, Darryl!