In the P.A.W., it would be nice to be able to make a nice loaf of bread or even just cook something without using a campfire and risking burning your food all the time. This isn’t as far-fetched of an idea as you may think. In fact, you could build an oven to use while you’re travelling if you have the time.
The basic premise of cooking in a conventional oven is cooking by convection. When you bake a loaf of bread in a modern conventional oven, the heating elements in the oven heat the air closest to the flames, causing it to rise, moving the colder air near the flames and repeating the process until the air inside the oven is a relatively uniform temperature. You then place the bread dough in the heated air of the oven. The heated air transfers its heat into the dough, causing the temperature of the dough to rise to roughly the same temperature as the air around it. At this temperature, the ingredients in the dough cook and eventually you have bread.
The easiest and quickest oven you can build is an earth oven. You don’t need anything too special or permanent to build it – just some mud and a fire. The basic concept of an earth oven is that you are creating an enclosed space that holds the heated air required to oven cook anything.
Because dirt/mud is exceptional at holding, we’ll use mud to build the shell of our oven. We use mud because it is malleable until it drys, at which time it will hold its shape. The first thing we need to do though, is find a way to make our oven space hollow. The easiest way to do this is to use wet sand. We can shape the wet sand into whatever form we want and the mud won’t destroy that shape, and dry sand is just as easy to remove from our oven as wet sand would be. So we first make a mold for our hollow space, then we coat the mold with several inches of mud. The thicker the mud walls, the more heat it will retain for longer. Let the mud dry into a hardened mound, then cut an opening into one side of the mound all the way to the sand/molding material. Dig out all of the sand/molding material and you now have an oven! Build a fire inside the oven to heat the walls of the oven. Once your oven is to temperature and the outside of the oven is hot to the touch, put out your fire and remove all of the fire material from the inside of the oven. Place your food inside the oven and cover the hole up to avoid letting any heat escape. Eventually, your food will be cooked.
The Pompeii oven is a precursor to the modern brick oven, commonly used in pizzerias. The Pompeii oven works on the same principles as an earth oven, and is actually the evolutionary successor to the earth oven, but it is more permanent and used with the fire still inside the oven while cooking.
For convenience, a Pompeii oven is built at around waist height or higher (because who really wants to crouch all the time while they are cooking?). This is best acheived by building a dais out of brick or stone or some other material that is fire proof and resistant to age and the elements.
Then you want to build a slab that the oven will be built onto. You might be fancy/lucky enough to have concrete and rebar to make this slab from, otherwise go for a material that is fire proof and resistant to age and the elements.
When considering bricks or brick material for building your oven, there are two factors to consider:
- Can the material withstand high temperatures? (refraction)
- How well can it reflect heat? (conductivity)
Ideally, you want a high refraction, low conductivity material because it won’t be destroyed by the heat of the oven and it will reflect heat given off by the fire efficiently. Firebricks (bricks made of a type of clay composed of high levels of alumina and silica) are the ideal material, but ceramic and clay will work just as well.
Lay out a pattern of bricks on your slab for the floor of your oven. Most people use an offset pattern for the floor because it prevents a seam in the floor which can cause your food to snag when putting it in or taking it out of your oven. Ultimately, it doesn’t matter how you lay them out as long as they are tightly lined up with each other to prevent heat leakage.
To form the dome of the oven, you can either build it free standing, or over a wet sand mold as with the earth oven. Building the dome free standing, you will lay the bricks one layer at a time and let the mortar dry before moving on, occassionally adding a wedge between rows of bricks to account for curvature. Don’t forget to leave space for an opening!
If you don’t have access to modern mortar, you can use clay, mud, pitch (tar), or you can make your own. Essentially, you just need something that will bind to your bricks to make a solid structure.
When building the door and door frame for the oven, you want to ensure that your door is at least slightly bigger than the opening in the oven. This will ensure that the door doesn’t swing into the oven and, when closed, forms a seal to heat and moisture leakage from inside the oven. Don’t make it an airtight seal. An airtight seal will cause what is known as backdraft: The flame will go down as it burns through the existing oxygen, then when you open the door the onslaught of fresh oxygen causes the fire to roar back up, potentially exploding out the opening of the oven and burning you. The door itself can be made from whatever you can manage: a hunk of scrap metal, dried mud, a rock, an old oven door, etc.
It is also a good idea to build a chimney into the door frame so that smoke and hot air have an escape path that isn’t your face. _Don’t put a chimney into the oven itself!_ This fundamentally defeats the functionality of the oven.
After your oven is built, you need to purge it of any excess moisture. This curing process ensures that your oven doesn’t crack when in regular use. To do this, build a small fire for 6 hours each day for 5 days. Start at 300F and increase by 50F each day. If you can’t accurately guage temperature, just build a small fire and increase the size each day for 5 days.
Once you’re ready to actually start cooking with your oven, start you’re fire near the front of the oven and once it gets going, push it off to one side or the back and let the oven heat until the outside is hot to the touch. Then cook to your hearts content!