The saga of my new wood fired oven
Shock Horror! Luna the wood fired oven has been decommissioned!
A closeup of Luna’s firebox recently after having the new V baffle fitted.
After over 7 years of use, Luna was facing yet another bout of major surgery. While this could be considered fairly routine for a well used oven, those who follow this blog will know just how much work I have put in to keeping Luna functioning.
After only a year of use since refitting her with a new steel baffle, the same baffle was completely destroyed by heat. This was a 10 mm thick piece of steel which my boilermaker advisor and collaborator assured me would do the job (at least for a few years) instead of going the whole hog and putting in stainless . Cost is always a factor in these decisions, and our judgement call wasn’t the right one. I expected it to last for at least a few years, as I was only using the oven for a day or two each week. But I watched that baffle gradually burn out over the past couple of months, working around it as best as I could for that time, and found myself thinking deeply about my history with every oven me and the boilermaker have ever created this last 12 years or so.
Bertha II and her firebox repairs. Big firebox, and a bugger of a job!
Berth 1, Bertha 2, and Luna, being the names I’ve given to three woodfired ovens I have had a direct and long term association with, have all caused me lots of physical and financial pain. I have crawled inside each of them, as well as other ovens made with our template - in a couple of cases while they were fully hot - and it’s never a pleasant (or healthy) experience. While all of them, after much post production work, have functioned well in the end, they each have had massive problems. These problems usually stemmed from the fact that metal degrades and warps over time, or is simply a very unforgiving material to work with.
Thus, I decided to avoid the material as much as possible in all my future ovens. I’m totally done with the complexity and cost associated with ovens which are essentially using lots of metal to hold masonry in place. Woodfired ovens have been made for centuries successfully with just brick and mortar. Why reinvent the wheel?
I’ve been working on a full masonry design for the past 12 months, and have finally built a small prototype to see how the masonry version of a ‘white oven’ will work. The design has morphed into something quite different over that time; when I look at what I’ve created I can see the original concept, but that’s about it. The way I got to the concept twisted and turned quite a bit.
The new prototype at the firebox stage.
The materials to make the oven evolved - I started with the idea of using common bricks with oven bricks used in various strategic places, which had merit; cheaply sourced common bricks can do the job, especially if you also use high temperature bricks on the parts of the oven where there is a lot of heat. But this prototype was to be built on my trailer, and I was worried they would require a lot of bracing to hold them together. Trailers bump around a lot on the road. Also, weight (at that time) was an issue, and I wasn’t sure brick was light enough.
Then I considered cast cement and AAC (Autoclaved Aerated Concrete), both of which I could cast myself. This attracted me as I could cast exactly to size; if I could cast fairly thin sheets I could save weight. I designed some molds which enabled each piece to lock into each other. The further I went down the casting rabbit hole, though, the more complex things became. The casting process seemed like a lot of fiddling, and was fraught with traps for newbies like me, so this idea morphed into using pre cast cinder blocks and manufactured AAC (Besser bricks and Hebel, being two brands commonly available locally). Off the shelf, at least in theory, it was possible to get pretty close to the correct size for the project. I tweaked the original design a little to accommodate them - then came to a road block - my design worked on an uncommon size of besser brick, being thinner than the usual construction kind. I only needed about six of them, but they were critical to the flue design in the oven. Do you think I could find anyone who would stock or sell me 6? The smallest amount I could order was a full pallet. So I went off looking for other ways to skin this cat.
I’m wandering around various landscaping and building suppliers in my new home town of Gloucester, looking for stuff to build my oven with, when I notice an unusual brick with three large holes. Immediately I see how it could work in my oven. While I wasn’t able to buy it, the retailer put me in touch with their maker - Lincoln Brickworks, just down the road at Wingham.
A quick drive and I’m chatting to the brickmaker himself. Before long he’s showing me their kilns - which coincidentally are wood fired till they get to 700C, then oil fired to take them up to 1300C. Lincoln bricks are one of the last independent brickmakers on the eastern side of the country - and they make their bricks in small batches, catering to the niche of the trade interested in truly bespoke, rustic materials, and craftsman techniques from the past. I’m sold, and the brick maker helps me load up 40 of them to try for my ovens. When I go to pay, they wave me through, saying ‘you’ll be back - we’ll sort it out then!’
Brick sides are on and rendered.
The bricks were used in the final prototype, and they worked as intended. They are stacked directly on top of each other in the side walls of the oven, creating flue pipes for the flue gases to travel along. The flue pipes lead around the oven, transmitting heat from the flue gas directly to the baking chambers. This meant that the baking chambers would heat up quickly, and that I would be reducing a whole layer of brick from my design, making it lighter.
I also built the firebox out of common brick, and lined the insides with firebrick. For a baffle above the firebox, I did some research into concrete, as my local hardware store sold 600 x 600 (2 foot x 2foot) slabs which were about 100mm thick. This was about the right size for the base of the baking chamber, and would save me a whole lot of time and expense with fabricating some sort of lintel to support a brick baffle. This was my first major error.
Then, bang! The concrete baffle exploded!
According to everything I read, concrete could withstand 600C heat. From experience, the internal temps in all my previous fireboxes reached 500C, so I figured I had a bit of wriggle room. I was very wrong. On the first trial firing, maybe half an hour in, I heard a large deep ‘boom’. I checked the baking chamber, and a hole had blown right through the concrete! So much for 600 C! It’s possible the slab I had purchased was not adequately cured - because I had taken temperatures inside the firebox some 5 minutes earlier and it had barely reached 200C at that stage. Far too low, I would have thought, to cause the concrete to react with the heat. Despite this fairly intense reaction, the oven held together.
I visited our local ‘Tip Shop’ (a most wonderful community resource where waste is sorted, displayed and sold for super cheap) and found some really heavy duty BBQ plate steel. I was able to support this underneath the slab, and thereby create a secondary level of baffle. I then used a high temp mortar mix to fill the hole in the slab, and put 30mm oven bricks on the top.
Shelves are added and bricks used in place of a firebox door.
Thankfully, this very quick and cheap repair meant that I could use the oven. I had quite a few subscribers to my bread delivery service (see previous post on my CSB) who, having not received bread during the entire period of relocation and oven building, were starting to lose their minds. I didn’t want to lose them as customers, or to have them lose their minds due to bread starvation, so I was in a hurry to get the prototype fired up and baking.
Over the next 6 bakes or so, I grew quite fond of my prototype tiny oven. It was relatively quick - 15 loaves an hour vs 20 per hour in Luna, which was 4 times the size. It was fast to heat up too - from cold to bake temperature in 2 to 3 hours. It also gave a wonderful kick to the loaves - my original spacing between the shelves was now too small, as the loaves were bigger than they were before by approx an inch! The prototype worked better than I thought it would, and really didn’t require a whole lot of modification, beyond repairing dodgy little bits of my super low budget repurposed construction materials.
But there were some problems. The primary issues were:
A baking chamber door is attached. It opens to a flat 90 degree platform.
getting the door to seal correctly. Smoke from the firebox would creep in under the baking chamber door and taint the bread. The door was a piece of fairly thin steel from a previous oven which had been used as a shelf. The seal between it and the masonry was less than perfect, so I used some ceramic rope and high temperature tape to bog up the gap. It worked, after a couple of less than satisfactory attempts.
creating steam in the baking chambers. Due to my lack of welding equipment (and the lack of welding knowledge) I struggled to fabricate a way of holding water in a piece of pipe. The pipe system has been used successfully in all my previous ovens, but they required a welder to make them. This time I was in a new town and I didn’t know anyone here. Eventually I purchased some rectangular hollow galvanized bar and filled the ends with cement to block them off. Then I cut some grooves along their length with an angle grinder, which allowed steam to escape. They worked extremely well. They held close to a litre of water, which provided enough live, gentle steam to the baking chambers for some 15 minutes at a time.
properly insulating the surrounds of the oven. I built the oven to fit into the existing space on my trailer. There had been a small oven there previously which I used for demonstration bakes and workshops. To save time, I simply beefed up the existing insulation around the wall area and re-did the roof insulation. The floor had a layer of insulation too, as well as a sheet of rubber to isolate vibration from the oven. The oven base was 100 mm hebel, which is, in itself, insulation. The outer shell was made of this also. I figured I had it all covered.
I did not. After the first couple of production bakes, I observed smoke around the top of the oven. This worried me, so I removed the entire roof and replaced it with brick and corrugated iron. So much for weight! I could no longer tow the oven, but at this point I was quite happy for the oven to be semi permanently set up at my new home base in Gloucester.
Fired up for the first time!
After another couple of bakes, I noticed smoke coming out from UNDER the oven. While the top was now fine, smoke coming from under the oven really confused me. There was so much insulation and brickwork around the firebox, it just didn’t make sense. I added another layer of brick to the base of the firebox and the problem seemed to go away. Or it became less obvious, as I now know!
Needless to say, I was inspired by my little protoype. However, I could see that my construction techniques were not up for the long haul, and that I would need to be doing a lot of spot repairs to keep the little oven alive until I could make a bigger, more robust one.
Last week, after finishing the bake in record time, I felt I had mastered the oven, and made all the necessary tweaks for performance I would need to do for a while. I went to bed early and was keen to get the bread delivered the following day. A good bake is a wonderful thing for the psyche.
An early test run alerted me to the need to rebuild the chimney!
I woke to a loud ‘boom’ at about 2.30 am. I could see flickering light through the curtains, and stepped out to find the trailer and a couch in the undercover garden area fully blazing. As I ran to grab the hose, a second couch exploded into flame - I had put them perhaps 8 feet away from the other side of the trailer just two days earlier.
The fire from the trailer had engulfed them and caused the explosions. Luckily the local fire brigade came in 20 minutes or so, but those 20 minutes were I think the longest in my life, as I pointed an ineffectual hose in the general direction of the blaze. The fireys brought it under control in about half an hour. I wandered around on the footpath outside with loaves of freshly baked bread at 3 am for them as some form of thanks.
First bake!
(photo, on B+W film, courtesy of Maira Wilkie)
I lost the trailer, as well as a fair proportion of my power tools. I also lost some printing equipment, and a good deal of pride. I thought I had insulated the section around the oven well, and indeed I did. The problem was under it. I built the oven on AAC (hebel), with fire bricks on top. There was a layer of wool insulation batt under the oven, with a thick rubber matt under that, and foam under that, and finally the timber frame built on the trailer years earlier. The weight of the oven had slowly flattened the insulation, making it less effective. The heat from the firebox had found its way through all the insulation, and had created a smouldering heat issue which had slowly, over quite a few weeks, degraded the timber framework underneath. This simply gave way, the oven tilted backwards, and hot coal spilt out of the firebox, setting the whole trailer alight.
Disaster! Half a dozen bakes later, the fireproofing under the oven fails, and the oven tips over, catching the trailer on fire and destroying it completely.
Apart from feeling stupid at my errors of construction, I felt defeated. It’s taken me 30 years to be at a comfortable place with my craft. I get to bake commercially just once a week, with civilised hours. I have many happy subscribers to my bread delivery service, which has continued each week now for two years or so. I try to impart good info to anyone who wants to know. I’m deeply immersed in my craft, as anyone who has spoken to me will be quick to agree. Many 300 series students have gone on to start their own successful micro bakeries, as a result of my inspiration and guidance.
Over the years, thousands of home bakers have come to learn at my 101 workshops held each month, and many stay in touch, attending numerous workshops to keep their bread making processes improving and growing . I’m deeply happy to be part of the bread making renaissance in Australia. When I began, bakeries were heading away from natural bread; there was not an interest in using organically grown grain or in artisan milling or fermented bread at all. Now there are hundreds of successful bakeries turning out great bread all around Australia, and when I speak to them they are rightfully proud of their product. There are a number of mills creating superb, sustainably grown flour from quality grain. Of all this, I can say I was one of many who worked to make it happen.
The bakery business has been tough on me, and my body. I’ve earned a living though, and I’ve largely been my own boss for a long, long time. I’m rich in what I know, and I’ve been further enriched by the responses people have to my bread, my teaching and my professional guidance over many years. I’m not materially rich, though - I discovered some time ago that I have little interest in material gain beyond what I need to keep going. This I know is both a problem, and a solution to bigger problems.
Thus I find myself questioning whether I should go on; to rebuild, or to find another way of earning a living. I feel like I have been a professional crash test dummy for too long. It’s my own doing, I know. And I do question my sanity from time to time.
In Western Australia teaching Bush Baking a couple of years back, with the trailer on its second incarnation.
So I’m asking you, dear reader, to really help. I have decided to seek contributions to a crowd funding initiative, to help me build a new oven and to rebuild the site, so that I can get the School of Sourdough properly established here in Gloucester. I need to buy materials to build the oven, as well as some new tools and some professional assistance so that the new setup won’t have any issues down the track. If you think I should continue doing what I do, then follow the link below and make a contribution. If I can raise $20K I’ll be over the moon. If I can raise half that, I will still be able to get things up and running again. Any amount will encourage me to continue. Even nice words and a bit of virality by sharing this post will go a long way.
People who can contribute will be rewarded in any way I can - small contributions will get free bread to equal value when the oven is finished - provided you are somewhere in the Hunter Valley region. Bigger ones can receive one on one tuition/consultation to the value of their contribution down the track, here at the bakery or over the phone, if necessary. Really big ones will receive eternal gratitude and whatever else I can give to say thank you. And everyone will be supporting a community enterprise as well as a journeyman baker who needs to know if he’s mad or not. Please chip in and help me get this project finished!