Home Woodfired Ovens
Sooner or later, most keen home bakers experience someone else's home made wood fired bread. Envy kicks in. Or, they might simply visit an actual woodfired bakery. The effect of well made, sole baked bread from a woodfired oven is primal. Not to mention pizza = but that’s a whole other story.
Driving a woodfired oven is something akin to flying, only you are kind of 'surfing' heat. Baking with a wood oven, which usually has substantial thermal mass, is often referred to as baking on a 'falling' oven. That's because the oven is fired till the insulation or core is very hot - often above 500 degrees celsius - and the oven is then used to bake throughout the baking chamber's long 'fall' in temperature.
Typically, the baker would begin with pizza and flat breads like focaccia; then baguettes and rolls - things with a small mass, which cook quickly and fill the oven with steam. Then on to viennas, batards, and the tinned loaves, as the heat settles a little. Finally, fruit breads, cakes and biscuits, which need lower temperatures. The remaining heat was then used to prepare vegetables and other general tasks. Or, in a busy bakery, the oven would then be fired again for a second round.
In effect, the baker's art when using one of these is all about what to bake, when.
This 'baking on the fall' is typical in what is known as a 'black' oven - one that has no firebox - like your typical pizza oven. Black ovens are so named because they make the baking chamber (at least temporarily) black, from the carbon deposited on the walls of the oven when the timber burns.
There is another style of woodfired oven as well. It's known as a 'white' oven, because it has a firebox separate to the baking chamber. White ovens, with their separate firebox, don't go dark inside the baking chamber, as the flue gases are usually kept out.
Just to make things more complex; there is also the great Australian 'Scotch' oven. These ovens were commonplace, dotted around the Australian countryside. They were often attached to homesteads, or general village houses. These ovens were quite large; they had the same baking area as your typical double bedroom's floorspace. They baked for whole towns, sometimes; often the bread was delivered farm to farm, house to house, by horse and cart. The ovens were built by master oven smiths, generally from Scotland, who carried with them the IP to create these ovens wherever they may be. These craftsmen travelled the country with basic masonry tools, as well as transportation, in the form of horse driven carts, and later trucks. They would settle in a township or population center in a strategic fashion, and gradually find themselves a customer base for their skills - building furnaces. They would build and repair all sorts of working fireplaces in the towns, and would often lend their hand to larger jobs like bakery ovens. The scotch oven in Australia - and I can't say I've researched them overseas at all - could really be termed a 'grey' oven. Mostly, the fireboxes in these ovens are separate to the baking chambers, but are flued directly through the baking chamber. So it's both a white oven and a black oven - thus, 'grey' (More about these wonderful ovens in another article).
'MOISTURISING' YOUR WOOD FIRED OVEN
I have a funny feeling that there will be quite a few people out there who have tried unsuccessfully to bake bread in a woodfired pizza oven. There are lots of traps for the unwary, especially when operating a 'black' pizza oven for the first few times. In their enthusiasm to build a really good fire, people often take the temperature way too high, and then put things like bread in while it's really hot. Pizza can handle 400C; bread can't. Charred dough is generally the result. Another common issue is crust colour. People simply can't get a good, reddish brown crust colour. That's because many of these ovens either do not have a door, or don't have one that seals well. To bake pizza, which is what these ovens are primarily designed to do, you don't need a 'rise', so you don't need moisture in the hot air.
When baking bread, though, you have to have steam. If you want to get a decent loaf out of a pizza oven, you'll first of all need to create steam inside the oven. Get a whole lot of empty tin cans, remove the lids completely, and fill them full of water. Place them in front of the hot coals to shield the bread, while also creating masses of steam. Keep them topped up the whole time you bake, refilling them between loads. Works a treat!
HOME WOOD FIRED OVENS
Home wood fired ovens seem to come in two main types. The first is the aforementioned 'adobe' style oven, usually with a dome shape and no door; this type is very popular, and usually pretty inexpensive. You can buy them in kit form, or have them made up for you, or even off the shelf at a hardware store. Great for pizza, not great for bread, but as I mentioned earlier, with a bit of juggling you can make do with these. They don't usually come with much of a chimney, and often don't come with a door either. With a bit of ingenuity, though, something can be fabricated/altered to fit the hole. This isn't the forum for how this might be achieved - suffice to say you can make a door out of all sorts of things. Allow your ingenuity to take control.
The second type of woodfired oven is an enclosed, 'black' oven, which is suitable for both pizza and bread. These come in a range of shapes and sizes, and have various added extras, like the ability to fill the chamber with smoke and evacuate it. They have stone tiled floors, and are built primarily from brick. They have an internal 'arch', rather than a 'dome'. They often have some sort of flue control.
Then there are a range of 'white' woodfired ovens, which are made from varying qualities and thicknesses of steel. You get what you pay for here. The hardware store variety (cheap) will do the job, in a kind of small volume, 'rough as guts' way. And they will get you started. But then they will die an early death, as they are not designed to actually last. On the other end of the scale, you can get something like an Aromatic Embers oven, which is really heavy duty, and will last forever. These ovens are not cheap, by comparison with the hardware store version, but compare favourably with the price of constructing something like the oven in the previous paragraph.
Of my initial research, many ovens are cheaply built, and have stress points which are not properly reinforced. Over time, cheap ovens display why they are cheap. Many adobe and brick ovens leak air like sieves, and are really not useful to the home baker. Many have too little thermal mass - and while you don't need a lot for the backyard roast, some are less than a centimeter thick. Insulation is also necessary with these black ovens. Without it, the oven will be very unstable and use lots of wood. A well insulated (an inch or more thick) oven will use less wood.
When researching this article, I interviewed Craig Miller, from Aromatic Embers. His hobby, and now his business, is making quality woodfired ovens. Having picked his brains thoroughly about these things, I have to say it appears as though this guy has applied some real common sense to the idea.
You can buy a woodfired oven from a hardware store these days - but a quick glance at the quality and thickness of the insulation, as well as the fittings, you can see that these ovens have been built to a price rather than a standard. I have spoken to many people who have purchased one of these, used it a dozen times, and found that stuff had already bent out of shape or just plain broke. Heat breaks things. If you are going to buy a woodfired oven, make sure it is made of very sturdy material, or it will not last long.
I have worked on quite a few wood fired ovens now, including a couple of versions of Bertha, my first co designed bakery oven. I've also used larger commercial wood fired ovens in my bakery for many years - and the quality of output and the speed I've been able to achieve with them is quite amazing.
What follows, then, is some general information about woodfired ovens and how to use them, based on the past eight years of using them to bake my bread. (note: this article has been revised now - going on for 12 years as I revise this post!)
WOODFIRED BAKING AND HOME WOODFIRED OVENS - SOME IMPORTANT POINTS
My research into these ovens tells me the following important things:
Thermal mass and thickness of insulation is important if you need to run the oven continuously for long periods. Most families just want to do their pizzas, maybe a roast, and possibly bread after that. This might only be a few hours. You need more thermal mass if you want the oven to run for longer periods efficiently, though. The advantage of greater thermal mass become evident in the quality of the bread the oven bakes, though. More thermal mass means the heat has 'momentum', and therefore bakes better and quicker.
Loss of moisture is more critical in a wood fired oven than it is in other ovens. Loss of moisture occurs through porous surfaces and air leaks. If you're purchasing, ask about this. Some adobe ovens are treated for porousness - many, including lots of home built versions are not. This means that any steam you are able to generate will mostly be absorbed by the oven itself. Some adobe ovens 'cure' over time, as the more they are baked in, the more the surfaces become sealed.
Door seals must be tight. If you have an old oven, the seals tend to wear. You can get special ceramic rope which can be glued into place using high temperature silicone. This rope is heatproof, and it compresses to form a seal. You can usually find it at specialist wood fired heater stores, which are becoming fewer these days as everybody moves to central heating, but they can still be found in most regional centres.
A thermometer which sits on the floor of the oven is very handy to gauge hotspots etc. Even better is a laser temperature gauge, available at any auto parts store for not much money. Well worth the investment, if you are serious about your woodfired baking.
Keep the oven tiles CLEAN inside the baking chamber and in the firebox too! Sweep the baking chambers out before and after baking (each load) with a coir broom, or something with coconut fibre or horse hair bristles. Nylon will simply melt. Don't even think about it. The semolina from the dough eventually will burn and create a LOT of smoke, so ya gotta sweep! Also, if there is a firebox, clean it out completely before use (when it's cold). You need to collect any ash (good for the garden) or remaining coals, and clear out any air supply grids as well. It's easy to do, and means you have a better chance of getting a nice clean burn from the getgo.
Invest in the right oven gear - good gauntlet mitts, a coir or heat resistant broom, quality baker's peels with nice, fine edges, an ash shovel, a banister brush and dustpan, etc. I was going to say they make life easier. But you actually can't do without any of these things.
Practice loading fully proofed bread using a peel - and remember that baking a single loaf or two will not produce enough steam for a rise, so you will need to use the technique above, plus spraying the walls of the oven with some sort of garden pump action sprayer, to get solid amounts of steam. The tin can technique is very useful.
The more you fill the floor of the oven with bakeable stuff, the more the temperature will drop; however, the flip side here is more steam will be produced as the stuff cooks which in turn creates bread with a better crust. For best results, the oven should be FULL. When I say 'stuff', I mean anything from bread to roast meats, veggies, etc. They all give off moisture as they cook. Their flavours will be a little intermingled, but it's better to have a full deck than a half full one. Results will be more consistent and predictable this way.
Learn to bake with a 'falling' oven. Get to know when to put your bread in. Don't go too early - a hot oven won't make your bread rise more, it'll just crust it quicker, achieving exactly the opposite! A 'bread oven' is between about 280C and 220C, measured in the centre and on the base of the baking chamber. In general, you will fire up your oven to be hotter than this, to take advantage of all the things you can bake 'on the fall'. Thin stuff gets baked first (pizza, flatbreads etc). Temperature ranges for best results with these foods might be between 400C and 280C, as a rough guide. Next, you might do bread rolls, baguettes and things which need a nice thin crust. Temps here might be between 280C and 250C. After that, you might start to bake breads, roast meat, vegetables etc. We are talking between 250 and 200C. If you still have heat, you might then bake sweet things, like pastries and cakes, or slow baked meats, casseroles, fruit breads and so forth. All these things do better in a slow oven. Finally, remnant heat can be used to dry stuff out. You might begin with fleshy fruits and vegetables - peaches, tomatoes and so forth. After that, you can still slow roast seeds and grains; and finally herbs and really lightweight, low density things. So you get an idea of what baking on the fall is all about. True village bakers were masters of this craft - they would wring every drop of usefulness out of their ovens, as everything was focussed on getting the most out of limited resources - including firewood and even heat itself! Your home woodfired oven would do well to get through this entire fall routine though. They just don't have enough thermal mass/insulation. And they don't really need it either. They are, I suppose, designed for what they are likely to be used for. Whish is the weekend pizza party.
An alternative to trying to utilise the oven for all this baking, is to do your baking, and then to use the waste (residual) heat to convert food waste into what is known as 'biochar'. Biochar is incredibly useful stuff. I've been using it on a commercial scale as fuel for my own oven for some four years now. (Jan 2018), and I find it virtually essential when it comes to building and maintaining a fire for many hours continuously. (There is definitely another article in this!) Biochar can also be used effectively in compost heaps too, because the worms love to wriggle through the gluten bubbles, making them into worm nests rapidly. These biochar nests provide the worms with a kind of thermal insulation so they can maintain their ideal core temperature no matter what the season. But I digress.
'White' ovens are different beasts altogether. They can be used to bake continuously, as the fire runs during the baking cycle. They can be made to run at any given temperature range for as long as you care to maintain the fire and the baking production. You can bring them up or down in temperature as required. Having said that, some white ovens have so much thermal mass and baffling inside them, winding up or down the temperature takes a bit of time to have an effect. In 'Luna', my own 3 'baking metre' oven (smallish) is a relative Ferrari - changes in firebox temperature can be felt in the chambers after only 15 minutes or so, depending on how dramatic that change needs to be, of course.
Over the coming few years, you will see all manner of new woodfired devices coming into the world. The concept of 'fire science' has taken hold, particularly in the US. 'Rocket stoves' are becoming a 'thing', as they are super efficient and capable of getting huge temperatures from a few sticks. The name 'rocket' came about because of the sound they make - the design essentially 'stretches' the flame, and causes a kind of fire vortex when proportioned correctly. My own oven, 'Luna', was designed originally as a 'rocket oven'. We ditched this idea after the first firing, as we simply couldn't get the heat to transmit properly into the baking chambers. However, people will persevere, and I'm pretty sure a home rocket woodfired oven will appear soon on the market. The potential of super efficient, super clean woodfired ovens is huge, and I expect we will see lots of action in this space!
Note: Since this article was written, I have begun designing DIY commercial and semi domestic pvens made from easily sourced materials. I have one set of plans available for download. These plans are backed up with consultation and support all the way through your build. I