Although I have been using my gas barbecue (Grill) for making pizza for a while, there was always something lacking.
The spring in the crust was not as good as it should have been and no amount of experimentation in dough recipes seemed to be giving me all the results I wanted.
I needed a oven that would produce high enough temperatures which would cook the pizza in under 5 minutes. A brick oven seemed the best way to go.
Nirvana seemed to be a wood fired brick pizza oven.
I did not want to buy or build a traditional wood fired pizza oven, as this was overkill for the amount of pizza we make and eat in a year, even with the occasional pizza party.
Thus I began my quest to construct a simple but effective way of getting a hot oven and give me the results I was looking for, all this without sending me broke, or having to keep stocks of hardwood on hand to fuel the oven.
The dome shape helps to focus the heat from the BBQ and also retains heat within the bricks as well.
The pizza cooks in multiple ways. The base cooks mainly from the heat of the bottom stone, the top cooks from the radiated heat from the dome itself, and the hot air which comes from the back of the oven and through the front and then escapes through the small gap in the BBQ hood.
Step 1: Materials You Will Need
The BBQ Pizza Dome uses a hooded 2 burner gas BBQ as the heat source. I found mine on Ebay for A$60 (minus a few non-essential parts such as the warming tray )
4 x refractory oven tiles (300 x 300 mm) used in the floors of commercial pizza ovens
1 bag of High temperature mortar mix.(they only seem come in really big bags)
4 lengths of Hollow Square Section steel. (1 Metre)
2 lengths of 12mm Solid Rod. (1 Metre)
2 lengths of 6 mm solid steel rod. (1 Metre)
Electric drill and Drill bits to match. 12mm and 6mm drill bits.
Felt tip pen (permanent)
Water spray bottle
Metal mesh (Chicken Wire)
You will need to cut 3 of the the tiles into strips so that they are square. For example my ties are 40mm thick, so I cut the tiles in to 40mm strips.
A 300mm tile will give you 7 strips of 40mm. I needed 15 strips for my dome, plus a few spares.
The remaining tile is used as a pizza stone, which will sit under the dome.
Step 2: Measuring and Cutting (1)
In order to get the best results it is important to check the BBQ you intend to use for the conversion for the following features.
A hood which offers good coverage of the cooking area.
An inner lip inside the BBQ & this is where the hotplate and grill plate usually sit.
I recommend that you scour sites like EBay and go to a few garage sales, as its likely you might pick up what you need cheaply.
Things like missing grill plates and side tables are often the reason other people choose not to buy, as most are looking for a BBQ to use in the conventional way.
You could user a number of materials to accomplish this, I just happen to have some spare HSS and some steel rod left over from another project.
The steps to construct the dome support are as follows.
Measure up the grill area.
Measure the grill area, and the inner support lip, taking into account any bolts or welded joints that may impede the placement of the steel support frame and furnace bricks
Measure and cut the steel to match the grill area.
I used Hollow Square Section and some 12 mm solid round section (both mild steel).
The square section was cut to length (less 2 mm for expansion) and then drilled to take the 12mm round section.
Note: If you have access to an electric welder, you could produce a more rigid frame using HSS and reinforcing mesh.
Step 3: Measuring and Cutting (2)
Assemble the frame.
The frame consists of 4 pieces of Hollow Square Section (HSS) and 2 lengths of 12 mm solid round section.
2 of the HSS pieces have 12 mm holes drilled completely through both the inner and outer faces and the remaining 2 pieces have holes drilled only on the inner face)
2 lengths of 12 mm solid round section were inserted through the 2 HSS with and then the HSS with the single hole was placed on the end of the rod.
When properly fitted together, the frame drops into the lip of the BBQ at roughly the same height as the original grill plate and hotplate.
Step 4: Measuring Up for the Dome and Producing the Template
Once the frame is installed you will need to confirm the maximum height the dome can be with the hood down. This will depend entirely on your BBQ and the type of hood that is fitted.
Take care to look for any bolts or fittings which may impede a tight fit against the back wall of the hood.
You also need to take into account the thickness of the refractory material you are using.
Create a dome template (Paper)
Based on your measurements in taken earlier, use a computer based drawing program to assist with the template creation and ensure that your scale is 1:1
Draw a rectangle to represent the maximum height and width of the space in the BBQ.
The rectangle should have a vertical centre line drawn through it to assist with alignment.
The straight side of the dome should be twice the thickness of the refractory material. In my case the refractory tile was 40mm thick. So the straight sides need to be 80 mm.
Using a tool draw a curve from the top of the inside edge of the wall to the centreline of your rectangle where it intersects with the top. Once done, copy and mirror the shape and align it on the other side.
I have included a visio drawing with dimension to assist you and an enhanced metafile document for those who don't have visio.
If you have a printer which only can print half of the template, you will need to ensure that you include the centre line in both prints so that you can align them using this line.
Print 2 copies of the dome design and cut off the excess paper as neatly as possible.
Align the two prints together using the centreline as a guide. Use sticky tape to hold them together.
TIP : If the paper you are using is thick, and you cannot see the centreline on the bottom sheet through top sheet, use hairspray or oily nail polish remover to make the top sheet transparent while you align it with the bottom one.
To create a wooden former for the dome using the paper template you can use apply the template to the ply using watered down PVA glue.
Coat the surface of the plywood before applying the paper template. You will need to work quickly before the glue dries.
In order to make two identical templates, screw a second piece of ply to the first so that you can cut out both pieces in the one operation.
It is important to remember that all adjustments to the ply template must be made to both, otherwise the fit of the refractory materials will not be neat.
My dome consist of 3 main sections, the left hand side (5 pieces), the right hand side (5 pieces) and the top dome (5 pieces)
The taller ones (80mm) are the two straight pieces and are made up from two 40mm tile strips
Lay the tiles (dry fit) on the edges of the template to see if they fit correctly when laid on the template.
Mark the point where the last of the 5 left tiles ends on the temple, repeat for the 5 tiles on the right hand side.
When compled you should have something that looks like this.
Use spacers to build up each side with strips of tile until you have filled in the whole template.
Once completed, dismantle the dome and re-assemble in the BBQ and ensure that the hood can be closed. Resolve any issues with fit by trimming the template and adjusting the placement of the tiles. Once you are happy with the fit label the end of each tile so you know where it goes.
Step 5: Mortar the 3 Main Parts
Once the end tiles fit correctly, you can mortar them together.
Note: You must use a minimum of mortar on the inside edge to ensure a strong bond. The outer surface is less critical and can be filled with mortar once you have completed the initial construction steps.
Soak all the tile pieces in water for 30 minutes to ensure they are thoroughly wet. If the tiles strips are dry, it will instantly dry up the mortar as you apply it and the bond will not be strong.
I made my dome in 3 main sections, the left hand side (5 pieces), the right hand side (5 pieces) and the top dome (5 pieces)
If you construct the dome in this way you can move the pieces easily and it allows you to fine tune their placement in the BBQ.
Step 6: The Metal Dome Supports
I decided that I might need to reuse the ply templates should the whole dome collapse or I decide to build a second dome.
I made up two metal dome supports to help during the final rendering and firing processes, and it also saved me from having to move the whole dome to remove the wooden template.
I used 6 mm steel rod bent into the shape of the underside of the dome. The rod is fitted into holes drilled in each support section where the steel and the tile meet.
Step 7: Wire Up and Mesh the Dome
Tie the steel supports and tiles together to help support the 3 major sections.
If at this point you want to test the dome (like I did) you can fire up the BBQ and take it on a test drive.
Leave the BBQ on medium heat for 2 hours to heat through and remove any oil or reside which might taint the pizza.
When you are happy with the performance of the oven, you can move to the final steps.
Once the BBQ is cold. Apply the mesh to the outside of the dome using the steel rod as a tie-down.
Step 8: Render the Dome
Apply mortar to the joints of the 3 segments and apply the finish coat of mortar to the outside of the dome ensuring that no mesh is visible.
You can apply an oxide to the mortar to match the BBQ if you wish.
Keep a spray bottle with water handy to keep the mortar wet while you are applying and smoothing.
The mortar has a grey finish which is a bit boring, I decided to add a final render coat with some oxide as a colouring agent.
Step 9: Curing and Firing
Once completely dry you should fire up the BBQ and slowly heat it.
Leave the BBQ on medium heat for 1 hour and then check the dome for cracks and splits.
The one remaining refractory tile should be placed on the supports under the dome, this is used to cook the pizza on.
Step 10: Cooking Pizza
Now you are ready to cook pizza.
You may need to experiment with the stone height placement to ensure that the bottom stone is not too hot compared with the inner dome temperature.
The ideal temperature for me seems to be around 360 C which cooks a pizza between 3 and 4 minutes depending on the toppings and the dough hydration.
I always cook with the hood closed, I check every 45 seconds and turn the pizza around halfway through the cooking about 2 minutes.
Here are my first pizzas from the dome, cooling before serving.
Cooking with the dome is a definite improvement, I now have to re-learn how to cook them to get the best results.