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Sourdough Starter Tips and Troubleshooting

Having an issue with your sourdough starter? Here is a simple guide to the most common issues that arise with the activation and maintenance of a starter!  Below is a Activation Tips section to hopefully help you stay on the right track, and a Troubleshooting section for any issues that emerge.  

If you are new to sourdough baking please take a look at my page What is a Sourdough Starter? (And why you should want One!)

There is also a FAQ Page for questions about the 150 Year Old San Francisco Sourdough Starter!

Activation Tips

Good news!  Your starter is pretty chill, and does not need much to be become active and thrive!    Conveniently, for example, your starter's favourite food is the carbohydrates in flour and your starter only ever needs to drink water. While some bakers would add various other things to attempt to bolster their starters, the Kensington Sourdough starter has only even been fed flour and water, and is (I think!) the most active starter around with this simple diet! 

The most important thing to remember is that your starter is a unique living thing, and each environment is different!   Hence, when activating your starter you may have to adjust when feeding to ensure it is properly thick and stays healthy. Your starter is likely to behave differently from season to season, or even with different bags of the same type of flour!  Keep in mind the principles below, get to know your starter, and it will be fine.   Be brave and have fun!

Tip 1. Your Starter wants to be warm

70F-85F (21C to 29C) Is the ideal temp range for your Sourdough Starter to come to life.  If your kitchen is colder than this, or if you want to get it closer to the middle of this range, there are a few ways to get this done.

1. Oven with the light on!  BE CAREFUL EVERYONE!  While this is a great solution for keeping starters happy, it has also been the cause of untold carnage as spouse after spouse inadvertently pre-heats the oven and accidentally bakes the poor little starter.    Another concern is that for some ovens the light is warm enough to cause the temp to eventually reach 120F+ which could harm the starter.  If you suspect your oven light is one of these overachievers, simply turn it off after 10 - 15 min.  The oven will hold the warmth.

2. On top of the fridge.    This is a good spot for a mature starter as the fridge will give off a slight amount of warmth.  It can also work for activating your starter if your kitchen is not too cold and/or you don't want to use your oven.

3. Microwave with door slightly open.  Your microwave light will also provide some warmth, and the bonus is nobody is likely to pre-heat a microwave!

4. A Fancy bread proofing box.   If you want exact control many bakers use a proofing box like the well-reviewed Brod and Taylor one here.   A proofing box is  an investment for sure, but many bakers swear by them!

Tip 2. Your Starter needs water

Your starter wants good clean water!  You should use lukewarm water in the feeding process, and the colder your kitchen is the more lukewarm the water you can use for best results.  Here are the key points with water:

1. Avoid chlorine.  As simple google search of your location should tell you whether your tap water has chlorine or chloramine added to it!  We don't want this as both can be harmful to the little lactic acid bacteria we want to flourish!

Chlorine in a water jug will evaporate in 24 hours.  Chloramine will not evaporate and will need to be filtered out.  I use a Pur Water Filter for this purpose (it will filter out chlorine and chloramine and most other contaminants) and to just generally have better water for baking.

2. Bottled Water, Spring Water and (maybe) well water are fine!  Bottled water should be chlorine free in most parts of the world, and both spring and tap water should be great!  If however you are having issues with your starter and using one of these water sources, you should try switching this first, as there is a chance that your particular well water might have a concentration of minerals that the starter does not like.  

3. Avoid excessively hard or soft water.  You likely already know if either of these apply to your water source.  Overly hard water can have a level of mineral ions that can mess with both the health of the starter and the results of baking.  Soft water on the other hand lacks minerals, although in theory the starter should still activate fine, it may need these to thrive.  

Tip 3. Your Starter needs flour

I feed my starter all purpose flour.   This is mainly a practical decision, as I go through a lot of flour just for the maintenance of my little beast.  I also want consistency with what the starter is used to, and what my customers are likely to have at home to activate it.  Here are my flour tips:

1. Use All Purpose (AP) flour until the starter is active.   Your starter is used to eating the AP flour as food, and it is unfair to ask it to adapt to a new food source while also coming back to life.  Note: AP flour is closest to Type 550 in Europe, 0 Flour in Italy, and "Plain Flour" in the UK!   Both bleached and unbleached flour will both work fine.

2.  Consider using a fresh bag of flour.  If you are not sure how old the bag of flour is in your pantry, it's worth it to get a fresh bag of flour for stating your starter.  While white flour has a long shelf life, the older the flour is the more likely it is to have a mold spore or two kicking around.... not what we want to introduce into our starter jar while it is still getting strong enough to defend itself from all comers!   

3. Experiment with switching flours after it is active.   Sourdough Baking can be as simple and rustic, or as complex and scientific as you like!  A Rye starter, for example, can be more vigorous, while a whole wheat starter may help impart more flavours to your loaves.  You can either convert the starter you have just by gradually feeding it a new flour, or just split off some of your existing starter into a new jar to experiment.

Tip 4. Your Starter wants to be thick!

This is veering into personal advice, as in theory the wild yeasts and lactic acid bacteria are perfectly happy in a starter with any hydration level.  I believe that a thin and watery starter is undesirable during activation stages as the starter will be less able to fend off outside invaders.  For a mature starter a thin starter will likely produce less sour flavours.  For anyone attempting to convert to a gluten free starter, a very thick starter is a must!

My advice is to always adjust while feeding so that your starter is like a thick paste.  Much thicker than pancake batter -- closer to warm peanut butter and hard to stir is a good guide.  After feeding as the starter feasts on the flour and water your starter will gradually thin out over the next 24 hours.  This is normal!  If it ends up soupy by the time you feed again then feed it even thicker until it behaves!   You adjust by stirring in more flour, or less water, or both.    

Tip 5. Your Starter needs a home

The instructions I send call for starting the culture in a bowl, as everyone has one and it is easy to mix and stir.  As some point, however, you will likely move your starter to a Jar.  Storage Tips:

1. These Weck Jars are my favourite jars by far for a sourdough starter.  Both the Weck 745 Tulip Jar  and the Weck 743 Mold Jar are amazing, tough, and make it easy to use, feed, and stir your starter. 

Weck Jar Sourdough Starter active gold rush kit San Francisco Bakery


2. This Ziplock container works great! If you don't mind plastic, these are a really great starter container.   The flat sides and wide mouth make it easy to feed and stir, and the slight lip at the top mean you can securely fasten your parchment paper lid with a rubber band.  The plastic is tough and durable.  The one you want is the Medium Round Ziploc Twist 'n Loc 

Ziploc Twist 'n loc storage for sourdough starters sourdough starter jar and lid kit


3. Avoid narrow mouth mason jars. If you keep your starter thick like I advise, stirring is a bit of a workout!  The common quart size mason jar everyone has with the 2.5 inch mouth is just not wide enough to get your hands in and stir.  

4.  Avoid metal containers.  In decades past there were a lot of aluminum or tin lines baking vessels, and these materials would react poorly with the acidic elements of a starter, to the potential detriment of both the metal item and the starter!  Chances are you were not planning on keeping your starter in a vintage aluminum jug, but many of my customers are a good type of weird and I would not be surprised if at least a few of you were planning to do exactly that!

5.  Don't Seal the Jar!  Use a parchment paper lid instead.  Your starter will produce gasses as a result of the feeding and fermentation process.   The Weck jars are unlikely to explode even with the airtight lid clipped on, but a sealed mason jar or similar will absolutely kaboom itself.  Instead I use a large square of parchment paper and a rubber band for a lid.   Even when the starter rises more than I was expecting, the parchment will balloon up and "catch" the excess.  

Parchment paper also allows the starter to breath slightly, unlike plastic wrap which in my experience can throw off the moisture levels in the jar.   The starter won't stick to the parchment paper which is ideal!  



The below are the most common questions or issues that customers have reported to me, and how I usually advise them to proceed.  Please note that I will always happily ship you another starter if something goes wrong during activation!    Here are the common questions and issues:

Starter not activating or rising 

There are a few common reasons that a starter is not rising.  Please note that unless you baked it or it got a big dose of chlorine or cleaning residue, it is unlikely to be dead!   However we want it to double or triple after feeding -- if it is not doing that by day 7 here are some potential issues and solutions: 

1. Is it too cold?  If your environment is around 70 degrees or cooler it wont harm your starter but it will slow everything down, and your starter will be slower to become fully active.  See "Starter is thinning out between feedings" below for the opposite issue, where the environment might be too warm.  If the starter has been activating in a cold place it might take a few more discards and feeds past day 7.

2. Did you discard down to half a cup before feeding on day seven?  And each day after that?   Ok this is a bit my fault as the written instructions can be confusing in places.  I have done my best to be clear but don't feel bad if you didn't realize that you had to discard after the big dump on day 5!  You will discard before feeding on day 7, and before each time you feed after that. 

Another common mistake is discarding half of your cup instead of down to half-a-cup! A starter needs a good ration of fresh food to starter when being fed, and just chucking half of what you have wont do.  A half a cup of starter is not much!  It's only about 100 grams.   I will link to some video instructions soon that will hopefully be really helpful!

3. Could there be an issue with the water? See the tips section above for the common water issues which can absolutely slow down your starter!  Chlorine, chloramine, or overly hard or soft water can reduce activity or delay the activation timetable significantly.  If you suspect that your water might have an issue switch to a different water source for a few discards and feeds.

4.  Are you using AP flour?  I have noticed in many instances when customers are having issues with their starter not becoming active in 7 days they are using a flour other than All Purpose.   All Purpose is what the starter is used to!  Stick to AP until it is active.

5. Did it secretly get baked in the oven?  It's not unknown that someone will send me a photo of a clearly scorched starter asking what the issue might be, and I get to imagine a David Sedaris level family mystery as to who pre-heated the oven and attempted a cover up!  In any event an orange and dried out starter has likely seen some significant heat and is likely toast.  I have a special discount code for burnt starter replacement!! Just email to ask at!

Starter is thinning out between feedings

On occasion you will go to feed your starter and it will be a complete soup -- Not at all how you left it when you fed it nice and thick the day before!   This means the starter is moving too fast, and it is being a bad pet! A warmer kitchen can be the culprit here, but sometimes it just seems like the starter will do this for no particular reason!  To stabilize it I will feed it even thicker.... hydrated, but close to a dough.  Repeat feeding it thicker and thicker until it behaves again.  

Starter has a clear or black liquid on top

This is called the "hooch" and is normal!  It is also a sign that your starter is moving quickly through it's cycle and is hungry.   When this liquid is present your starter will smell quite acetone, which is also normal and nothing to worry about!  The "hooch" is called as such as it is an alcohol byproduct of the fermentation process in your jar!  Note that it can also occur at the bottom or middle of your jar.  You can stir it in before discarding and feeding, although if it is older (ie the hooch formed after the starter was left alone for a few days on the counter or for a few weeks in the fridge) then dump it off before feeding.  

Starter has a crust on top

Good!  This is just dried starter that formed when your starter rose quickly and then subsided slightly, allowing enough air to dry out the top layer.  I use parchment as a lid and always have a crust.  I stir the crust in when feeding.  My pet theory is that crust is frozen in time from the exact moment the starter was at it's peak!  So nothing to be concerned about...perhaps quite the opposite! 

Starter smells weird

I love it when my starter has a strong acetone or nail polish remover smell, but this can be unnerving to first time starter owners!  A starter can also smell slightly like bread -- it all depends on the yeast bacteria balance that day and where the starter is in its fermentation process.  

A normal starter may also smell a bit musty, like yoghurt, ripe cheese, or even sulphur!  If your starter smells overwhelmingly bad, however, like rotting food or garbage, then its time to check for mold.

Starter doesn't pass the float test

I don't use the float test!  The "float test" is meant to determine the activity level of a starter by seeing if enough gas has been produced to allow a chunk of starter to float.  Based on many emails with customers I have not found this to be reliable.  A starter can be perfectly healthy and not "pass" the float test.

My typical email inquiry is something like "Hi, my starter is doubling in size vigorously after feeding, is full of bubbles, smells amazing, and is making the best bread I have ever had!  but it doesn't pass the float test... is something wrong?"  Usually I reply that it doesn't seem like anything is wrong, and note that I don't use the float test!  Instead, I want customers to get make sure the starter looks and smells healthy, has bubbles, and is doubling in size after feeding.  

I forgot to feed my sourdough starter

The starter will be fine if you miss a few to several feedings on the counter.  In the fridge, a neglected starter will usually be fine for months!  When you discard and feed a few times it should come right back to normal in either case. 

If it has been longer than that, it would be smart to give it a visual check for mold, and make sure it smells normal (it will likely smell quite sour after a long period without feeding, but that is not cause for alarm).  If you see mold or it smells a LOT like a dumpster, then it's best to start again.

If your starter is sluggish after some time off, you can kick-start it by feeding it twice a day!    Pantry Mama has a good protocol here!

Mold in the Starter

Mold is rare but can happen.  Usually the culprit is either an external source such as from a nearby food items or spores in the flour used to feed.  Another way mold can form is if chlorine or cleaning residue (such as from a dishwasher) on the starter jar has weakened the culture to the point where mold can find a home.   A neglected starter in the fridge will eventually be vulnerable to mold, although my customers have had starters sit for 3-4 months which have been perfectly fine.  

Mold is very rare for a healthy and active starter being fed regularily, as your starter will be the toughest micro-culture on the block, and a stray mold spore has zero chance of getting a foothold.  

If there is visible mold on your starter and in the jar, then it is most prudent to chuck it.   In the past many people would scrape away surface mold, transfer to a new jar, and carry on.... but the question of course is how they can judge that the mold is indeed surface only.  Please just email me .... if there is mold present during activation I will happily send you a new one!  


Thanks for reading this guide!  If you have any questions that aren't addressed above please email me at!  


Finally, for some of the recommendations above I have used Amazon affiliate links.  I have a product recommendation page here: Sourdough Tools and Gifts to (Maybe) Buy.   I thought I should disclose this, as if you purchase after clicking here I may stands to benefit with a small profit on the purchases made.  Please be assured I would never let a tiny expected income motive interfere with my only real priority, which is getting you all baking and enjoying sourdough bread!