Dry on top

aceaston's picture

I have a starter I use twice a week. It's doubling when I feed it and turning out tasty loaves. The only thing is it's started "drying out" between feedings. I use it twice a week as I said, and feed it both the day before I plan to use it and also the day I use it, so I'm feeding it at least 4 times a week. It sits on the counter in a glass canning jar (the kind with a glass lid, rubber gasket seal)  in the meantime. It's not particularily dry or humid where I live and heat is a comfortable room temp.  On days when I don't feed it, it gets a dry skin on top.

Should I be concerned?


363 users have voted.


maphew 2013 October 21

Dear Anne

I found your question pretty interesting, since I have encountered the same drying out on the surface in quite many instances.  

I see this happening at home with my own starters when doing home baking; however, I see this equally happening to the sourdough starters we use at the artisan bakery where I am working. 

For roughly two years, I have been on a professional road to artisan baking since I started working in an all artisan bakery as the bread bakers apprentice. Fortunately, this time of being an apprentice is over soon, and I will have chance to advance my bachelors bakers career :)

Anyways, the advice I would like to share is, based on my own experience, that this dry skin on the surface, should not have any considerable impact on using or further developing the starter. 

Covering the container certainly is an easy and sufficient way to prevent the starter from forming too thick a surface layer. What would work even more efficiently, is to directly cover the starter with a piece of fresh wrap foil. This way, there is no direct contact to oxygen, that might alter the surface.

Covering the starter with a piece of fresh wrap, I used to apply to my starters at home. They even stay fresh and untouched for some days without feeding.

However, in professional baking we simply close the bucket containing the starter with a lit. That suffices to protect the starter during the interval between one production shift to the other. The dry layer that might form on the top, will dissolve anyways, once the starter is being used in the sourdough. 

This wil happen to your starter, too, at home baking. The dry peaces of starter, will simply dissolve in the process of kneading and developing the dough. Therefore, there should not  be a reason to be worried about, in my opinion. 

I hope this might be of any help to your questions.

However, I am glad to learning more on this concern from other bakers, too.

Thank you :)


^^The dough we nurture; the bread we share ^^


Molly 2017 November 5

This was such a thorough and helpful response. I'm new to sourdough and only in the last couple of days have experienced this skin developing on the top of my starter, as the season has shifted from summer to fall - not sure if that has anything to do with it though. My intuition told me that the starter was fine - as I could see also, that the film would simply dissolve as I stirred it back into the dough beneath it - but it certainly is relieving to see others are experiencing it too, even professional bakers ;)

Thank you Maphew <3

Simer 2020 May 22


I'm new to sour dough baking. Ended up baking my first loaf last week. After that stored my starter in the fridge. 

when I was ready to bake my second loaf I fed my starter with 2.4.4. It was taking too long to revive so I consulted a friend who is also a baker. She advised me to go with 1.4.4 or 1.5.5. I did that too. My starter is taking too long to grow almost 6-7 to grow 1-2x. I can however see lots of bubbles. Also the starter dries up on top which I happen to read in your previous post.

pls suggest what I should do to revive my starter well for baking 


aceaston's picture
aceaston 2013 October 24


It seems to me that this skin was not simply drying out. The jar I kept it in was sealed and there would be moisture/condensation on the inside of the lid and yet the sour was still skinning over. It also starting happening after only 24 hours. I suspect it was actuallly a mold forming and I disposed of that starter, and started using my backup starter that I keep in the fridge. Since I tossed the first starter and thourghly washed the glass jar it was in, I have not had any issues with skinning.

Keeping my fingers crossed.


highsky's picture
highsky 2013 October 26

I had the same effect, but for me the issue was the change of the temperature.

Moisture on the lid is a sign of water evaporation from you starter, not?

Laurie Garber 2019 April 7
I proofed my SD loaf and the cover came off and a think skin formed on my loaf (dried out). What do I do?
gareth busby 2019 April 10

Hey Laurie,

One of my favourite tricks is to give it a mist with a plant sprayer filled with water. Giving it a spray every ten minutes for an hour or so usually does the business.

Alternatively score and get it in the oven now!


Staff 2019 April 7

Hi Laurie.

You could score the top of the loaf thourougly, cutting through the skin allowing the soft dough underneath to expand out during oven spring.

Or you could flip the loaf over to bake it, so that the (skinless) bottom becomes the top. You'd probably still score it a little.

If it is only a thin skin, you could possibly keep proving the loaf until it is so ripe that the skin starts to crack before it goes into the oven. This is a technique commonly used with rye bread...with the rye content of the dough helping to make those beautiful natural cracks open up. If you don't have a high proportion of rye, malt, or low falling number flour, then the cracks may not open up and you'll be left with a thickened skin on a soggy overproofed dough.

That last method is a bit tricky but makes great bread. I'm a fan of fermenting dough until it is close to falling appart. From memory I believe rye content should be greater than 30%.


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