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Sourdough Glass Bread (Pan de Cristal)
Glass bread, known as pan de cristal in Spanish and pa de vidre in Catalan, was developed in Barcelona, Spain around 2010 by the baker Jordi Nomen of Concept Pa Bakery. This bread is a variation on the narrow, crusty bread that this region has long favored for its traditional tomato bread (more on that below). The distinction of glass bread is that the dough is quite wet and there is virtually no bready interior. The crumb should be mostly transparent (glass) webs of gluten.
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Glass bread (91% hydration) used for a sandwich
I’ve been working on a sourdough version of this bread for a while now using Breadtopia’s bread flour and various recipes I found online that range widely in hydration and use of oil and sugar. At one point, I went all the way up to 108% hydration. That dough was surprisingly manageable because of an autolyse, bassinage, and extensive gluten development. However, my results with such wet dough were no more “glassy” than a 91% hydration dough that didn’t require a bassinage, or even my 75% hydration ciabatta, which uses some whole grain flour. So, as per my modus operandi, I went with less effort and drama.
Early test bake (106% hydration) of glass bread rolls
In retrospect, I knew that extra water doesn’t necessarily mean a more open crumb. Baguette and pizza doughs are often hydrated around 67-70%, and their crumbs can be wildly open due to good gluten development, extensive fermentation, and a very hot oven. In fact, if you want to see a comparison of crust aeration on pizzas cooked at about 750F versus 500F, check out this blog post.
Final bake of long glass breads at 91% hydration
In analyzing the different recipes I tested for glass bread, I realized the ones in English pushed the hydration of the dough over 100% while the ones in Spanish hydrated the dough at around 90%. I’m not sure why this difference exists, but you can see I ended up on the Spanish side of things. Including the flour and water from the sourdough starter in the dough, my final glass bread dough is 91% hydration. Breadtopia’s bread flour is 13.5% protein, and if you have a lower protein flour, you may want to drop the water in the recipe.
The crunchy crust and webby crumb of the final recipe
The video below shows the dough consistency of this final glass bread recipe. You can see that the dough transforms from a goopy batter at mixing to a sticky-but-stretchable blob during the third (of four) coil folds. It’s fine to use a stand mixer or slapping and folding instead of Rubaud mixing if you prefer.
How glassy your final bread is may also depend on your oven rack position and heat. For this recipe, I preheated my oven and stone for 45 minutes instead of 30 minutes. I used an infrared thermometer to check the temperature of various parts of the stone, and this longer preheat seemed necessary to get the stone to 500F or more everywhere. Both a cooler preheat and having my baking stone on the middle shelf instead of one shelf lower, seemed to make for a denser bread base. Because of some almost-gummy bread bottoms, I also set up a different steam system than usual, putting a cast iron pan above the baking stone so as to not deflect heat to the stone at any point during the baking process.
Shorter preheat and higher stone seemed to result in a denser crumb in this test bake
Working with this very wet dough requires a minimalist approach during dividing and shaping. Here is a video showing how to shape long glass breads, and if you prefer to shape rolls, see the video link after the recipe. Note that when you lift and transfer the dough to the parchment paper, you may have to squeeze it and then stretch it out again like an accordion, ideally using two bench knives or a bench knife and a dough scraper.
Pan con Tomate
When I lived in Barcelona in the early 90s, I often ate Catalonian tomato bread, known as pan catalán or pan con tomate in Spanish and pa amb tomàquet in Catalan. Catalan is the language of this region of Spain. I was quite enamored with this traditional bread preparation and enjoy making it still. Pan con tomate seems to be in the family of Italian bruschetta, but with just the essence of fresh tomato and garlic, no chunks of anything.
Glass bread is ideal for pan con tomate because it’s so crusty and therefore leak proof, and it has minimal crumb and is therefore unlikely to get soggy. To make tomato bread, you cut the bread lengthwise, toast it, rub the open faces of the bread with raw garlic and tomato, drizzle on olive oil, and sprinkle with salt. That’s it but it tastes magical!
Here’s a video showing how to make it with one of my test batches of glass bread (108% hydration).
Sourdough Glass Bread (Pan de Cristal)
Glass bread or "pan de cristal" from Spain is a fun high hydration challenge for bakers and it rewards your courage with crusty, scrumptious loaves for perfect Catalonian tomato bread aka "pan con tomate," as well as bruschetta, garlic bread, and any sandwich you want to be crispy and never soggy or leaky.
Ingredients
Baker's Percentage by Ingredient
Instructions
Autolyse
Mixing, Gluten Development, and Bulk Fermentation
Shaping and Final Proof
Baking
Photo Gallery
Research Sources and Supplementary Videos
Video of the bassinage and gluten development for my batch of 108% hydration glass bread.
Video of cutting and shaping rolls of glass bread.
Joy Ride Coffee video for 106% hydration sourdough glass bread — in English.
Forner De Alella video for 85% hydration yeast glass bread — in Spanish.
Thread on the Fresh Loaf message board discussing the important of oil and sugar in the recipe.
Shopping List
Sourdough Starter (Dry)
High Protein Bread Flour
Danish Dough Whisk — Large
Dr. Oetker Dough Scraper Successor
Extra Long Bench Knife by Lamson — Walnut Handle
Flour Sack Towels — Natural & Organic
USA Pan Cookie Sheet
FibraMent Oven Baking Stones
Infrared Thermometer with Laser
Evo Oil Sprayer
ThermoPop® 2
Parchment Paper Sheets — 200 Sheets
$19.00Sourdough Glass Bread (Pan de Cristal)