Oil Drum Pizza Oven

This project is a remix of an Ugly Drum Smoker (UDS) and a Gym Ball Pizza Oven. I started making an UDS in 2019 but at the start of this year I decided to go vegan for January and never went back. As much as I love pulled pork and slow cooked BBQ meats I have found that there isn't much need for an UDS in the vegan cooking life style! So I decided I needed something else as a foodie focus and found that I really loved a simple Pizza Marinara so I set out to build a pizza oven.

I looked at the common vermiculite Gym Ball (like this one on Food Related) or clay cob approach and whilst it looked good I wondered if I could use the barrel I had sourced and cleaned for my UDS project to create a hard wearing and good looking Pizza Oven. I couldn't find anything else like this so I decided to adapt what was out there and see what happened.

The overall cost of the project was pretty low - about £70 excluding the optional stands - significantly less than any commercial outdoor pizza oven. The legs could be made from timber, blocks or steel but I picked commercial Builders Trestles as they were easily available and rated up to 400KG. The drum is very heavy when it is finished. The process was relatively easy and I did it over several weekends to allow each stage to dry out before moving onto the next one.

Supplies

• Oil Drum with removable lid - mine was free but available on e-bay for around £10-£30
• Vermiculite - I used just under 2 x 100L bags of Micafil granules (approx. £20 each from Selco)
• Cement - I used 1 x 25kg of Multipurpose cement (approx £5)
• Fire Brick - I used 6 fire bricks from e-bay, recycled from storage heaters (£3)
• Paint - I used 2 x 500ml cans of Very High Temp paint from Halford (approx. £10 each)
• Legs - (optional to raise the oven) I used 2 x No.1 Builders Trestle Stand (approx. £25 each from Selco)

Step 1: Prepare Your Drum...

I wasn't 100% sure what had been inside my drum so I decided to clean it as much as I could and that meant starting with a fire. I burnt a load of scrap wood and got it hot enough to loosen all the paint on the outside and the lining on the inside. Once I'd burnt it out I got in with a wire brush on the end of my drill and took it back to bare metal as much as possible. It took ages but I think it was worth it. None of the cooking takes place on the metal as it's separated from interior by several inches of insulation. Once I'd done this I painted the outside with the high temp black paint.

Step 2: Prepare the Vermiculite Mix...

The mixture of cement, vermiculite and water creates an insulating layer that keeps the heat in your oven and cooks your pizza. The better the insulation the quicker the over heats up and the longer it will hold the heat. I went for about 100mm thickness as much as possible.

Looking around I ended up with a mix of 5 parts vermiculite, 1 part cement and two parts waters. I used an old plastic tub and mixed it with a trowel. If you make a ball of the mix with your hands it should hold its shape - its a pretty firm/dry mix.

I started with the barrel vertical and created the surface that is effectively the back wall. I used a bit of wood with a hole drilled into 100mm from the bottom to mark the barrel. The barrel was filled with the mix and then the end of the wood to flatten it down. I left this to dry for a good few days before the next stage.

Step 3: Make the Cooking Surface...

At this point I transferred the barrel onto a horizontal surface and marked the level where I wanted the floor to sit - I made sure it was wide enough for a decent sized pizza. Fill it with vermiculite mix until you get to the point where you can sit in your fire brick. I used 4 at the back and then 2 rotated 90 degrees at the front to make it slightly wider. Putting the firebricks in before the mix is totally dry helps stick them into place. I filled around them with vermiculite mix and built up a couple of ledges to use as the start of dome. Again I left this to dry (about a week this time).

Step 4: Make the Curved Roof...

To make the curved roof I used a wooden form. I got lucky here and had an old bass drum skin that I cut in half. It fitted perfectly with the right amount of gap and using both halves end to end it filled the full length of the drum. I covered the wood with plastic wrap to help get it out afterwards. To get the vermiculite mix into the gap it was easier if the drum was stood up vertically again.

Before I put the second wooden form in I cut a hole for chimney which was formed around a coffee tin. I pushed it into the hole once I had filled the mix up to that point. Again I pressed the mix flat with a wooden

Step 5: Add the Legs...

I originally intended to re-use some old aluminium chair legs for the base but it turned out that the overall drum and vermiculite mix was seriously heavy. Two of us struggled to lift it onto the legs which bent in the process. To make sure the unit was safe I bought some heavy duty builders trestles (you can also find them cheap on ebay) but I was too impatient to wait! I added some wood planks to one side to make a side table which has been really useful for holding pizza's when they come out.

Step 6: Get Cooking...

I left the oven to dry for a few weeks and then started with a small fire. The first time I cooked it took me about 2 hours to build up the temperature. Once the oven was heated up I measured about 450oC on the roof and 150oC. The temperature on the outside of the drum has so far never gone about about 75oC at the top of the dome and on the back wall its as low as 30oC. As its open at the front its not as hot as dome oven but it nicely cooks a 12" pizza in about 8-9 mins. The second time I used it it warmed up in about 45 mins.

I have been cooking on pizza trays so far but I might test cooking directly on the stone once I get a paddle sorted. The results have been fantastic and very consistent.

Comments

[gavin.rolph]

Hi, just wondering how you find cleaning this? Also, anything you would do differently if you were to do it again?

[martinlupton]

Hi, I've had no problem, just wait until its cook and push all the ash to the back and get it with a small spade.

[martinlupton]

also - if i was going to do it again, i might look for a different solution for cooking surface. The salvaged fire bricks work fine bu they do make the whole thing super heavy.

[Ed9876]

Nice one. I made a very very similar oven over the summer. Oil drum. Perlite concrete pour in the bottom for the back wall. Same for the floor. Fire brick floor The only differences are I also had a fire brick back wall and some fire bricks up the side. I also tried to get a 63’ ratio of dome height to opening. I looked at tressels too but then made a plinth out of old bricks dug out of my garden. I’ll post pictures if I can.

[martinlupton]

Looks good - all the pictures seem upside down but i like the chimney, its probably a lot more effective than mine.

[Ed9876]

Humm they are mostly upside down. I used more fire bricks to add thermal mass and accumulate heat for a longer fire. I also skimmed the perlite concrete with fire cement. As for temperatures. I have an IR thermometer that reads to 750F max. The floor and bad both get well over 750 and so I have to get it to cool a bit before cooking to about 550-650 otherwise etre base is tooo cooked too fast. Combustion is good with no smoke once it is going. Wood size is important. Not too big otherwise wit takes hours to heat up. You can also feed it whilst cooking.

[Marcel Hebert]

Be extremely careful selecting your drum.
if you do not know what was stored in the drum, do not use it.
A young student died when welding a drum to make a BBQ in school shop classes.
It exploded because the chemical had seeped into the metal itself and rinsing it out was not sufficient enough to make it safe.

[charlessenf-gm]

"...the chemical had seeped into the metal itself..."
Hmmm, interesting story. What chemical, exactly? Seeps into steel? Causes steel to explode when heated? Where, when, who, what, how? Sources, references please - I am intrigued.

[PlayersZ28]

Maybe this one in Ottawa ON. Sounds like the student was cutting into a sealed drum.

https://www.cbc.ca/news/canada/ottawa/eric-leighton-inquest-new-details-to-be-revealed-in-ottawa-school-explosion-1.2583378

[a.petersons]

Good job. Although some things I've noticed as authors lack of expertise in owens.
1) regular cement won't stay long, it will crack and deteriorate soon. Debris will go into food. Concrete needs to be moistened and kept in cool. Good solution is clay either fireproof cement (although this is expensive one).
2) Vermiculite mix is a great deal for insulation. As heat accumulator it sucks and food preparation generally is slow cooking over accumulated heat, especially for pulled meat either bread and pizzas. So these things are quite opposite - heat insulation an accumulation. Former does not allow to loose "quick heat" from burning process, although insulation material density is times lower than heat accumulator requires. Latter one provides slow cooling down. It is about effective mass, as bigger as better and this is good for even temperature in owen.

[albuck99]

Did you make a door for your oven? I noticed that you said that it was a bit cooler at the front, and a pizza should cook in about 3 - 4 minutes in a good oven. I just think a door, either heavy steel or something lighter with insulation, would make your lovely oven come right up to par.
Good post - I may well give your plans a go. Thank you.

[a.petersons]

3-4 minutes is way too fast. It requires high temperatures thus burning everything. Top temperature for cooking is about 140°C getting nice crust due to Mallard process. So, at that temperature pizza needs 10-20 minutes depending on style and filling. Precooked frozen ones probably will go for 3-4 minutes.

[albuck99]

Sorry, a.petersons, but couldn't disagree more. The following is an extract from one of thousands of sites detailing pizza cooking in wood-fired ovens. Whilst I agree with your comment on the Maillard process (spelled correctly), this can be achieved very quickly in a rapid cook. Of course, you have to be alert and watch your pizza every second:

High Heat Technique


This method has the oven at its highest temperatures approx
450°C. This temperature is excellent for cooking authentic pizza's, some
types of breads, appetisers and more within minutes. At this
temperature a pizza placed directly on the oven floor can cook in under
90 seconds, the pizza is cooked from the bottom up by the oven floor and
the top down by the oven’s internal temperature, resulting in perfect
pizza. This high heat method is also useful for browning and
caramelising items, unlike conventional means.

[a.petersons]

Are you sure it is Celsius, not Fahrenheit? Over 240° cellulose starts burning ;)

[albuck99]

Definitely Celsius. That's why it cooks in 90 seconds. Fast cooking like this is the secret of an authentic pizza.

[martinlupton]

I haven't made a door - wasn't sure if it was needed as I was always sat there watching the pizza! I will make one using the same technique used for the dome and see if it makes a difference then add it to my plans. Do you think it should have an air gap to allow a flow of air? Thanks for the great advice.

[a.petersons]

If you are cooking over accumulated heat then any opening steals valuable heat. If over the flames, then airflow is a must.

[albuck99]

I think most pizza ovens are used after the fire has gone out, using the heat retention of the insulation. If you think your insulation isn't up to it, I guess you could always add a sliding panel in the door.
Happy baking! Al.

[martinlupton]

Hi, You are correct I do have a lack of expertise - this is my first oven and my first instructable. With regards to the (much lower cost) cement I used that based on research of Gym Ball Ovens made from the same vermiculite mix and several (like the food related one) seem to have been working successfully for many years. I will keep an eye on it and update the instructable as it goes. At the moment it seems to cook pizza pretty well and they taste great.

[charlessenf-gm]

Wow! quite a piece of work your pizza oven! Now, get yourself an aluminum street sign, burn it clean and make yourself a peel!
If you start the firing in the front, or in the entire length of the oven, then push back the coals just before laying the pie down, you may get closer to that 'ideal' cooking time someone mentioned. I've noticed the Dome oven people seem to do it that way. And the person who suggested a door was on (IMHO) the right track - its the heat you're after.
Nice work, tasty looking pie! Good luck