Neill's Pompeii #1
Our planned 1000mm Pompeii oven is becoming reality after a relatively short planning period.
Thanks to Forno Bravo and this forum, the decision to build such a device will be a part of an upgrade of what is a fairly tired patio/pergola area that was built when we built the house 30 years ago.
The house is built on the high side of the road and excavated into the hillside, the double brick, reinforced concrete filled retaining wall is around 1200mm high and the oven is positioned in one of the corners. The top header course of bricks were removed and the foundations dug to give an adequate 3 reinforcing bar foundation which is also tied into the very substantial existing wall.
A sheet of Fortecon plastic damp course was placed over the clay base, 3 1/2” deformed reinforcement bars placed in the trench and tied to the starter bars which were drilled 150mm into the wall bricks and a double layer of F52 mesh placed over the rods.
I placed 2 x 1/4” copper tubes into the foundation to accommodate the thermocouples, one in the centre and the other to one side around 6” from the dome. This will allow me to establish the near surface temperature of the hearth, as the centre one will penetrate the brick to within 10 - 15mm whilst the other will measure the temperature between the fire brick and the insulation layer. This will give me a good idea of the amount of ‘soak’.
Re: Neill's Pompeii #2
Three quarters of a ton of concrete premix was collected and mixing of the conctete was done in my petrol 2.5 cubic foot mixer. Getting the concrete into the footings created a problem as I had to prepare a ramp up onto the existing barbecue benchtop which is 3” reinforced tiles concrete top. A substantial platform was placed on the top to cover the barbecue hole and the barrow pushed up the planks and then the concrete shovelled into the footings.
The next morning, I mixed the ‘exfoliated vermiculite’ to the formula that other members recommended. Started with a 6:1 mix, (vermiculite : portland cement) but when mixing, I added a little more to make it almost 5:1. This is a very unusual material to use. I mixed it in the poly tray wheel barrow with a broad bladed fork to prevent the vermiculite from breaking up as it is quite brittle. Mixing the two components dry was easy but spraying water onto the mix washed off the cement which was a little off putting until you mixed it again. Care needed to ensure that a pool of wet cement slurry was not remaining in the bottom of the barrow, but you should not have that much water in the mix. Wet enough for it to hold together but not too wet. I continued to add water until the mix held together when squeezed in a clench fist and a little liquid cement oozed through my fingers. Not too much water which would reduce the strength of the mix, but sufficient to do the job. I checked the layer out late last night (60 hours from pouring), and although it has a little compressibility on the surface, is quite firm and will harden up in the next week or two.
I collect the heavy angle iron today for the door frame and will bend the lintel and weld it to the angle support brackets for the oven doors to seal against at the oven opening.
The doors will be cast iron, complete with sliding vents to control draught which will be cast at a local foundry once I have made the patterns. Still running some ideas through my head as to methods of holding the rope seals in place.
To reduce the cost of the oven, (as the recommended fire bricks are around Aus$5 each plus around $250 delivery), I bought 200 second hand ones from an old abbertoirs hot water/stream boiler for $1.00 each. Had to sort them out from 3 palettes and got most in pretty good condition. Only trouble is that there is 5 or 6 different manufacturers and a slight size change between them. This will not cause any problems except for the hearth, as the bricks will be sawn in halves and sorted to reduce any size variation problems. I plan on bedding the best bricks on a very thin sand/fireclay bed (around 1-2mm) without cementing them in, and then dressing them to a nice flat cooking surface.
I plan on using a cement/lime/fireclay/sand mix for the mortar, without going for the latest refactory mortars. Lets face it, the ancient ovens were built without these materials and for the use and expected life of the oven, will do me and my family.
Will post more pics and running commentary as the oven progresses.
Re: Neill's Pompeii #2
Re: Neill's Pompeii #3
The brickwork has begun. Made the steel door frame and laid it out on the ground using some of the tapered fire bricks. Looks like it is going to work out. Note the two different tapers available.
I phoned to check on availability and price of fire clay from a local supplier, Aus$20 for 1.5Kg or $100 for a 20Kg bag. Way too much for this boy so I checked with the company who supplied my vermiculite and although they are not continuing to stock it, a surprising $30 per 25Kg bag was much better, so it pays to keep tabs on your suppliers. Called in and got some more cement and bricky sand on the way home, made the steel frame and then and laid out the arches. Started the brickwork yesterday and made the pattern support for the front arch this afternoon. Thought I’d get it done today and hey with a little effort, the last 5 tapered pavers from the pool surrounds some15 years ago, it is done all bar the final cleanup tomorrow.
I can now start the smoke chamber and flue, which I plan on using either heavy weight galvanized steel or stainless and then run the flue in stainless skyward. I plan on screwing it to the back of the facia arch bricks, the side and oven entrance arch bricks.
I collect the diamond saw in the morning from a mate so I will cut all of the bricks for the soldiers and also the dome bricks. Using the 9” angle grinder with a diamond blade is a little dangerous especially when you need both hands on the grinder and you hold the bricks with your feet.
I need to cut the top angle on each soldier and do a little special cutting for two adjacent the opening which will be grooved to accommodate the angle door frame. I want it to be able to slide if it expands without putting pressure on the dome. This will be achieved by putting a tag at the top of the angle to locate the height and allow the frame sides to expand down into or between the hearth bricks.
I will be using the standard mortar mix, as in Russel Jeavon’s book, but also with some fireclay in it as well rather than the lime. Will make up some samples and test them out tomorrow. Russell’s ovens are fine and are used 3 days a week without any problems for many years. I plan only to use it maybe twice a month unless something special grabs me to use more frequently.
All going to plan and hopefully get into the dome next weekend.
Will post the next episode once it happens.
Re: Neill's Pompeii #1
to follow the rest of my oven construction and see the pictures, go to the Brick oven photos forum, and see Neill's Pompeii#4.
Sorry for putting these in the wrong forum.
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