The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

blow out

kristakoets's picture

blow out

Anybody have any insight into why my loaves recently are blowing out? Seems only to happen with a "log" type shape and almost always along the lower side...probably busting the seam. I am slashing as deep as I dare, baking with convection, steam pan for first 12 minutes, 500 then turn down to 475. Rather wet dough, 67% hydration. Thanks!


thomaschacon75's picture

The common response to this question is that you didn't knead your dough enough, resulting in underdeveloped prolamins and glutelins, causing structural weakness.

That may be the case sometimes (and probably more so for less experienced bakers), but in my experience the blowouts are caused by excessive surface tension: so much tension that the loaf surface (loaf skin) is too tight, so it blows out where the skin is least taut. It has to expand somewhere, and as a levee will fail where it is weakest, so will the structure of your loaves. In short, if you're properly developing your dough (windowpane test, etc.), then it could be that you're simply shaping it too tautly.

Why would it be more so with the bâtard (log) shape? Not sure, but it could be because the bâtard is one of the more difficult shaping techniques (I'd say the most difficult after Challah braiding), so we overdo the shaping in hoping to achieve a proper-looking bâtard.

Surface hydration can also play a part, such that areas of greater hydration will blow out because areas with lesser hydration will be stronger. (Note. That sounds right in my head, but not sure if what I'm saying here will make sense to you, if at all.) In any case, this is why it's important to avoid overexposing your loaves to the air, which will cause the skin to dry, resulting in any number of deliterious surface problems, both structural (blow outs, texture) and appearance. Reinhart, from his earliest publications, promoted the use of spray oil and plastic wrap to prevent drying. I use both myself, more so now that I live in Denver, where humidity seldom gets above 50%. 

Just Loafin's picture
Just Loafin

Hard to tell due to lack of information and/or pics of your process, but you might be under-proofing.

A properly proofed final shape will have lots of bubbles all throughout, and will allow heat to penetrate very quickly. A final shape under-proofed will be dense, and therefore the heat will slowly penetrate towards the core from the outside. This means the crust will become inflexible before the core reaches peak yeast activity. It's kind of like a pipe bomb at that point, as that core energy has to get out, and quick, causing a blowout at the weakest place.

If heat is penetrating correctly, we can control the energy release with the slashes, and bring it out the top. If you are reasonably sure that you have properly developed dough, and your shaping is reasonably sound, then I'm gonna wager on under proofing as the culprit. Since a little under-proofing is somewhat desired for most recipes, I'd also suggest that you are under proofing quite a bit, ie., it should be obvious. What do you think about that, based on your baking experience, and can we get pics of that part of the process if you continue having problems?

- Keith

kristakoets's picture

Thanks for the input, all. Isn't it frustrating to have so many variables to contend with? My loaves bulk fermented for 3 hours, then a massive 18 hour retard in the fridge (got my timing wrong and no way am I getting up at 3am to bake...did enough of that in my twenties when I was the midnight baker at Avalon International Bread in Detroit!)

I am trying out the S&F technique, so consequently am mixing ingredients lightly, autolyse for 30 minutes, hand kneading for about 3 minutes...not very long at all...certainly nowhere near passes the windowpane test (and perhaps not long enough....I am not totally sure I understand if S&F replaces most of the kneading or is in addition to it?). Did 3 S&F at 30, 60, 90 min and then 90 min additional bulk fermentation at 77 degrees F.

FYI: almost all of my loaves are between 25~75% whole wheat flour, remaining flour is KAF bread flour.

My loaves tend to get very hard, cold and dry in my fridge....especially if they have any other ingredients, such as olives, fruits or nuts...I will try placing them in bags in addition to cloth lined and covered bowls. Although, this loaf in particular that blew out (25% whole wheat with cinnamon and maple syrup added) was pretty supple when it came out of the fridge...I let it warm at room temp for about 45 min as oven came to temp. I do not think I over-shaped it.

I am leaning toward under-proofing (even after the long retard) as I think my spare fridge is way too cold for much rising to happen. Next time, I will give the loaf 2 hours to come to temp after retard.

Will post pics if I continue to have problems...for some reason it is a bit of a challenge to post pics on this site :-)

I consider myself to be an amatuer baker who used to have professional experience...but I have been out of the paid trade for 13 years and have forgotten a lot! But, I sure am having fun re-discovering it!

Thanks again,


freerk's picture

Hey Krista,

And to add one more variable to the equation....

For some time, my batards did the same, and I found the source of the problem (in my case) to be my steaming method. After adjusting the amount of steam used and moving the source away (as far as that is possible in an oven) from the dough, especially when baking on the lower trays, the problem disappeared.

I think batards are particularly prone to breaking out on the lower curve. I agree with Thomas about the surface hydration. In my case I was "overhydrating" the bottom part of the baking bread. And rising dough is like electricity: it will take the easiest way out :-)


kristakoets's picture

Thanks Freerk!

I am in process of assembling a home-steam-injector...big deep rectangle pan with hole punched in it and a hand held steamer with a long nozzle (instead of paying $200 for a similar manufactured item) that I bought on ebay for $30! Hopefully this will regulate the steaming.