I was satisfied with the temperature I could reach with my stock Roccbox, but I wanted to decrease the warmup time (for my oven, about one hour in its stock configuration), and experiment with bake temperatures at the upper end of what might work. I speculate that the most elegant way to modify the oven would be to replace or modify parts in the burner assembly to make it burn more fuel at the standard propane pressure of 11" W.C. (about 1/2 psi). But the Roccbox burner assembly is a custom item, and the enclosure is riveted shut. So I left the burner alone and replaced the regulator with one that would allow me to use higher than standard pressure. Details below.
I've experimented with propane pressures throughout the range 1/2 psi to 2 psi. I currently run at 2 psi, although after you see what I'm sharing here, you might reasonably believe that 2 psi is a bit higher than ideal for this oven. At 2 psi, the oven is definitely ready to bake pizza after 15 minutes of warmup, although it is not fully heat soaked and at maximum temperature until a while later. With this configuration, I can achieve a 50-second bake. These have been my best pizzas -- at about the 50 second bake time. Higher temperatures, supporting even shorter bakes, are possible, but I personally have difficulty getting good results when managing an even more compressed time frame.
The Roccbox burner design creates a long, yellow flame, indicative of incomplete combustion, and in a sense, incorrect fuel-air mixture. But this seems to be by design. I do not understand why this is the correct design, but they all work this way, and it does work. Running at pressures between 1/2 psi and 2 psi, the stock burner maintains this flame profile.
At 2 psi, the oven delivers more than a rolling flame over the floor. The flame doesn't fit inside the oven. It just pours out the front. I've included photos of that, and a time vs. temperature graph. The graph ends at the 35 minute mark because I can't measure the temperature beyond that time. At 40 minutes, the stone surface temperature was too high for my infrared thermometer to read it, and the Roccbox's built-in thermometer, reading under the stone, registered slightly over its maximum indication of 500 °C. By 60 minutes, the Roccbox's dial thermometer had wrapped around, and pointed closer to 0 than to 500.
I let it get this hot only for the fun of the photograph. In practice, I run the oven full blast until the stone top surface temperature reaches about 500 °C, measured by IR, and then I turn the Roccbox's flame control down to its lowest setting. At 2 psi, the visual appearance of the flame at the oven's lowest setting is similar to the flame at the stock Roccbox's maximum setting. To cook a pizza, I turn the flame back up to maximum and then immediately launch the pie. This seems to be the key to getting hot bakes without burning the bottom. By letting the oven idle on low, and then blasting the fire at the time I launch the pizza, I get the top cooked in time before the bottom burns. I will return to the subject of heat balance momentarily.
I want to share more about the selection of a regulator. Most regulators that are adjustable are high-pressure regulators. The lowest-range regulator that I could find that is built in the style typical of regulators for outdoor cooking equipment is 0-5 psi. I have not tried that regulator. It might work just fine. But I would guess that, in supporting such a wide range, the degree of control it would offer in the lower end of its range -- in the region just above the standard pressure of 1/2 psi -- would be unsatisfying.
I wanted a regulator that was nominally 1/2 psi, or 1 psi, or 2 psi, with a small but precise range for adjustment around the nominal setting. I found what I was looking for in the format of regulators intended for whole houses, or very large appliances. These are gross overkill in flow capability for the Roccbox, which is a low-flow device. But they provide fine resolution of adjustment in the range of interest, and they are exceptionally stable (they stay at the pressure you set). The regulator I settled on is the Emerson-Fisher R232E-BBH. I created a shopping list at Amazon (
https://www.amazon.com/hz/wishlist/ls/3R5JKLH21Z1O2), to help anyone who might want to put together the parts to build this setup. I used a quick-release fitting on the oven-side of the hose, so that I can easily move the oven about without the awkwardness of dragging a hose and regulator along.
Now let's return to the subject of heat balance. The Roccbox is supplied with a cordierite baking stone. From reading this forum, I've learned that cordierite is not the ideal baking surface at Neapolitan temperatures, owing to its high thermal conductivity. I was hoping that I could improve my heat balance by replacing the stock stone with one of lower thermal conductivity. I purchased a FibraMent stone from
www.bakingstone.com, custom cut to the size needed for the Roccbox (13 13/16" X 13 1/16" X 3/4"). To swap stones, I had to drill out the rivets that hold the front of the oven on. With the rivets gone, the front face of the oven easily pops off. The new stone easily slides in, and the front piece can be replaced. I have not used any mechanical fasteners to hold the front piece of the oven on. The friction fit seems entirely sufficient.
FibraMent is reported to have a significantly lower thermal conductivity than cordierite. I was hoping for a dramatic improvement in heat balance, in the direction of less heat entering the bottom of the pizza. In actuality, I think I can tell the difference. I think the FibraMent stone is better. But it's not a huge difference. Not like what people report going from cordierite to biscotto saputo.
