Homemade pizza oven
We constructed a pizza oven with refractory brick and cement. After heating it up, some of the cement joints have cracked and leak. We didn't study the placement of the chimney or vent, so we have one in the back left, as seen pictured in many examples on the internet, but the oven smokes alot while building the fire. The oven does get hot - up to 800 degrees or more, but it is a hot smoky business using it. Also the leaks are there. Should we cover our beautiful brick with cement? Should we try to add another vent? How can we make this oven work better? We also have trouble with the pizza dough sticking to the bottom of the oven. Even though the oven registers at 700 degrees or more, after several pizzas the dough starts to stick. Thanks for any comments.
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Also did you follow a proven construction plan?
You could have many things going wrong at once. If you only looked at some pictures and built your oven it's possible/ probable that you could have done things better with proven methods. With that said I have seen stacks of brick with no mortar or insulation work effectively as a good pizza oven.
Questions I have.
Did you use any insulation under or over the oven?
Did you build the oven and go straight to a big fire or did you cure the oven first? (cracking issue)
How new is the oven? New ovens that arn't cured will smoke heavily when firing.
Sticking pizza could be a temp issue of the floor or a dough issue, how much if any sugar or honey in the dough. The temp issue is another sign of curing. After many pizza's the floor temp will drop so you may want to drag some coals in that spot and cook in a new location. Many people put the fire to the side and not in the back of the oven. This way you can add more wood easier and switch cooking sides of the oven as one side goes cool.
Hope that helps some.
Some people say that if we raise the chimney from 2 feet to 3 1/2 feet it will eliminate the smoke. We didn't insulate the dome, but built it out of fire brick and refractory cement. The Mayan who built it fit the bricks together very tightly and used as little cement as possible between the bricks. He made a keystone top. We fired the oven slowly over a week, but it still cracked when we built a bigger fire. I think we went big too fast, after several wimpy little fires. I think you're right about the floor of the oven cooling and that it might help to move the fire around. We haven't found the right tools to assist with moving the fire here in Maya Land, south Mexico. My husband has used a stick. We insulated the floor with sand and glass, and we are thinking of covering the brick with more refractory cement and then using facade bricks to make the exterior. Just wondering if there would be a problem with this. Thank you Faith in Virginia and Mini Oven. How long should it take to heat up the oven to cook pizzas and then how long should a well insulated oven stay hot. Our oven starts out at 100 degrees so there is that.
I feel your Pain,
As you can see from my Avatar that I have a WFO, I learned how to build from this site and members of that site are also here. www.fornobravo.com/forum/
From reading what you did, what you have is a heat sink and it will only cost you head aches and much money in fuel. Glass and sand are not thermal insulation as many believe. You should visit the site there is much to learn. Your builder brick work sounds wonderful. Can you add some photos of your oven?
Check out the fornobravo site and youtube: http://www.youtube.com/watch?v=2uNvPy9ed_U
You will see you need to insulate outside the firebrick to build more mass in the walls to retain heat. A few tiny little cracks won't end in disaster. What you need to do is find out what you want to insulate it with to hold the heat longer.
The bricks are so pretty and wonderful to look at so take pictures before you cover it up. You will also find that when it is completed and carefully dried out it will expand less when heated. The bricks will not have much room to expand outward.
Sorry to say, but from your description (although lacking in details), is sounds like you built error upon error in this oven. Where to start?
The bad news: A WFO chimney should NOT vent from the dome (sounds like yours does), but should be installed directly above the door opening, outside the dome. If you install a chimney inside the dome, you'll have the devil's own time trying to get the oven up to temp since the flue will pull all the heat out of the oven before it gets a chance to heat the walls. (A friend of mine who should know better tried this -- it just doesn't work.) Many masons try to use what they know about fireplaces to build ovens and that is a huge mistake. They are two different beasts. A taller chimney may improve your draft, but if it vents from the dome, that'll just make matters worse since more draft will mean an even colder oven. Also, even with a properly situated chimney, there are size limitations on the door opening: too big and the oven stays cold; too small and the fire doesn't get enough air to burn well. While it sounds like your mason did a great job fiting the brick, a single layer of brick probably won't cut it -- unless they are about 10" thick. There is just too much rapid heating/cooling for a single layer of brick to avoid cracking. Your dough is likely sticking because your floor is cold -- that could be due to low/poor insulation under the floor and/or not enough heat from the fire.
The good news: If it makes you feel any better, I doubt your curing method had anything at all to do with your problems. So long as they don't present any fire hazards cracks in the dome are not fatal, provided you can get the oven up to temp and the dome is constructed properly to maintain its integrity despite the cracks. If the dome is as well-fitted as you make it sound, this may not be a big deal. The smoking you are experiencing sounds normal. WFOs smoke a fair bit until the fire really gets going and is burning hot enough to burn up most of the combustion byproducts. (Does the soot burn off your dome after the fire gets going? If not, you need a bigger fire, different fuel, more insulation or a combination of these.) If you want to be able to see nice bricks on the outside of your dome, the best way to achieve that is to cover your existing dome with several inches of reinforced concrete to act as a seal and thermal mass, and cover that with another layer of brick "for show". Even better, add some insulation between the concrete and exterior brick veneer -- the more the better. You can mix a bit of portland cement with vermiculite to make a moldable insulation layer or you can buy a similar product already mixed as "Chim Mix".
If it was me, I'd invest in an infrared thermometer and do some experimenting with times & temps. Your floor should be around 600° for baking classic pizza and your dome should be around 900° with the fire burning brightly off to the side. You really shouldn't be able to feel heat coming off the oven other than a bit right in front of the door. Depending on the mass of your oven, you may be able to improve your results by simply burning a bigger fire longer to pre-heat the oven and keep stoking to keep it hot. My small-ish oven takes well over an hour at high burn to get up to temp for pizza. Once there, you can keep it there indefinately provided you keep an appropriately-sized fire going.
As for tools, a nice stick makes a perfect fire tool! I use one myself that I made out of an ipe board to sweep the fire and coals off to the side after preheating the oven. I use a garden hoe to rake out the coals and fireplace log tongs to move things around.
Finally, a set of pics would be a big help in trouble-shooting these issues.
Opps I don't know how to attach the pictures.
I am not clear on your exact problem(s) but a couple thoughs / suggestions.
1. If you think the problem is the chimney, try temporarily blocking the chimney by laying a brick or thick clay tile on the top of the chimney after you have started the fire. Obviously the chimney will be blocked and the smoke will escape via the front of the oven, but it can make things much more efficient in my experience. If the oven heats better / faster / hotter with the chimney blocked, I would consider removing it and patching the hole or placing some sort of permanent "plug" in the hole. You will have to deal with black soot on the front of your oven, but I prefer the ugly soot to undercooked or badly cooked breads and pizza.
2. You need a massive heat sink below the bottom of the oven floor so that heat will be retained for a loooooong time after you reach your target temp. If you didn't put one in when you built your oven, you may have a fatal flaw, but if your oven ceiling height is sufficient and you can fit them closely side-to-side and end-to-end (with some cutting obviously), try adding a layer of fire brick on top of your existing oven floor. Not a perfect solution at all, but better than nothing and if it works you will have spent twenty or thirty dollars.
3. Burn hardwood to heat the oven and if you have room at the back, to keep a small fire going during cooking. Again if you have a chimney in the center of the oven ceiling there is zero chance you can maintain temperatures, but if you block the chimney and get it hot enough, it should work.
4. In my experience the sticking problem is due to cool temperatures. At 900 degrees F nothing is going to stick to the oven floor except maybe your skin if you accidently touch it. If you can borrow an infrared thermometer and check temps it can be very helpful.