How long to get to temperature?

[man7sell]

Yesterday I fired up the pizza oven, probably on it's 10th cycle by now. It took some time to get the mass up to temperature, close to 3 hours. Even used a propane weed burner to help the fire along. The wood I'm using is cherry and I think that this is a good long burning wood but not so high in it's BTUs. Maybe I should start with a hotter burning wood and switch to cherry after.

How long does it take your oven to come to cooking temp?

[deejayoh]

Re: How long to get to temperature?

I cook with cherry wood and it takes maybe 90 minutes to get the oven up to temp. Sometimes less.

I don't always use cherry when starting the fire, usually I use fir or scrap lumber (SPF or cedar) and then throw the cherry on when I am getting ready to cook.

But I have always thought that cherry and other hardwoods are pretty high in BTU so should heat the oven pretty well?

[Les]

Re: How long to get to temperature?

I can get it to clear around 2 hours if I keep a decent fire going. I usually give it 3 hours and have a moderate fire. My oven is 42 inch.

[man7sell]

Re: How long to get to temperature?

Thanks for the replies. Maybe my cheery is not as dry as it could be. Mine is also the 42 inch so maybe 3 hours is what I can expect.

[Wiley]

Re: How long to get to temperature?

My 40 inch diameter WFO is steel domed and from match to first pizza takes between 40 and 45 minutes. I'm fairly certain the speed of heat up is due to the more rapid take up of the heat from the fire by the steel as well as quick conduction of the heat to the refractory. Using a draft door also helps with faster firing time. It's been four and one half years since first fire up and no problems so far.

Two nights ago I built a small fire with four pieces of madrone approximately three inch diameter and maybe a foot long with some kindling of alder. It was allowed to burn for one hour and then I moved what was left of the fire off to one side and moved two firebricks I had placed in the WFO before firing to form a barrier wall. With the coals on one side of the wall I slid in a pork shoulder in a S.S. roaster on the other side. Throwing some fresh green alder on the coals the pork shoulder was allowed to smoke for twenty minutes with lid off. I then raked out the coals, covered the shoulder (after pouring half a beer into the bottom of the roaster) and shut up the WFO. Yesterday morning: perfect pulled pork.

WFOs are great!

Wiley

[man7sell]

Re: How long to get to temperature?

Interesting Wiley, that a fast heatup for sure. Now a question, what's a draft door? like a door with a small opening?

Paul

[Wiley]

Re: How long to get to temperature?

Paul here's a link to a posting on my thread which has a photo of a prototype draft door.

http://www.fornobravo.com/forum/43/s...html#post41508

This was a prototype made in Hardibacker which didn't last long. I used the broken pieces as a pattern to cut one out of 1/8 inch (10 guage) steel plate. Hardibacker did not take the heat, it outgassed a malodorous smell and became brittle within a few firings. The new door had a curious characteristic in that it caused the WFO to "pant" much like a steam engine climbing a grade. The panting goes away after a few minutes with the intake becoming a constant rush of air into the WFO.
Here's a link to my WFO panting:

Panting Wood Fired Oven - YouTube

I could permanently remove the panting by increasing the size of the opening, as simply raising it about a half inch up from the entrance floor causes the panting to stop. I've left it as it is simply because I think it's cool...my oven is alive!

Draft doors are worth the trouble to build as they really increase the air flow causing the fire to catch and burn hot and fast. They do need to be made of metal as they do get very hot. I've measured a surface temp over 500F with a IF thermometer on mine.

Bests,
Wiley

[man7sell]

Re: How long to get to temperature?

Love the steam engine Wiley. So I have a plasma cutter and a hunk of steel plate that I was doing to use for the door. It's a disk so maybe I will have enough to build the smaller inner door for when you want to slow roast, and the outer door with the draft slot. Have to measure it up this weekend.

[david s]

Re: How long to get to temperature?

Paul here's a link to a posting on my thread which has a photo of a prototype draft door.

http://www.fornobravo.com/forum/43/s...html#post41508

This was a prototype made in Hardibacker which didn't last long. I used the broken pieces as a pattern to cut one out of 1/8 inch (10 guage) steel plate. Hardibacker did not take the heat, it outgassed a malodorous smell and became brittle within a few firings. The new door had a curious characteristic in that it caused the WFO to "pant" much like a steam engine climbing a grade. The panting goes away after a few minutes with the intake becoming a constant rush of air into the WFO.
Here's a link to my WFO panting:

Panting Wood Fired Oven - YouTube

I could permanently remove the panting by increasing the size of the opening, as simply raising it about a half inch up from the entrance floor causes the panting to stop. I've left it as it is simply because I think it's cool...my oven is alive!

Draft doors are worth the trouble to build as they really increase the air flow causing the fire to catch and burn hot and fast. They do need to be made of metal as they do get very hot. I've measured a surface temp over 500F with a IF thermometer on mine.

Bests,
Wiley

There is a downside to using a draft door in that it causes such a rapid rate of temp increase that you then risk damaging your refractory. It creates the same problem as using forced air induction which also shoots the temp up very quickly. Temp differential between the crown of the dome and the sides at the base will be considerable as refractory is not particularly thermally conductive (unless you have a steel dome). I think it is preferable to allow the thing to rise in temp slowly and safely. 400 C / Hr is way too fast and asking for trouble IMO. Most potters try not to exceed 100 C/hr.

[Wiley]

Re: How long to get to temperature?

Hey David S and Votavidone, I should probably post this under the Travel heading but thought that you were both following this thread I might take this off topic for a moment or two. Since you both live in Australia you might give better insight than most.

My wife and I are flying to Australia in late March and be in country thru early April. We are flying into Sydney and spending a day or so and then boarding the Indian Pacific to Perth and again spending a day of so and flying onto Darwin. There we will spend another day and board the Ghan to Adelaide. We will be traveling light and wondered what we should be expecting in regard to temperatures...don't want to take more clothes than needed. That late in the season should we be looking at shorts and tees or trousers and long sleeves? Sun screen or rain gear? Shoes or sandals? Any suggestions welcomed.

Thanks,
Wiley

[david s]

Re: How long to get to temperature?

Sydney should be beautiful then, expect maybe a bit cooler in Adelaide and Perth. At that time of year you could get anything. Darwin is always hot, definitely shorts and tshirts all year round there. Try to travel light and buy any extra clothes needed along the way as mementos.

[Bravo]

Re: How long to get to temperature?

I have a 28 inch by 20 inch cooking surface and it takes about 40 minutes or so to clear if my wood is dry and up to an hour if not.

I have been drying the next firing wood with any leftover heat from the current firing. So, that's helps with the time.

I haven't noticed any damage to the oven other then a crack down the middle which has knocked off a piece of the door frame.

[man7sell]

Re: How long to get to temperature?

I have a 28 inch by 20 inch cooking surface and it takes about 40 minutes or so to clear if my wood is dry and up to an hour if not.

I have been drying the next firing wood with any leftover heat from the current firing. So, that's helps with the time.

I haven't noticed any damage to the oven other then a crack down the middle which has knocked off a piece of the door frame.

Now drying the next wood in the residual oven heat, what a great idea. Kiln dried
Thanks
Paul

[Wiley]

Re: How long to get to temperature?

Thank you David and wotavidone!

Back to the topic. While I agree that it would be reasonable to assume that extreme thermoshock would/might have a detrimental effect upon the WFO built with a firebrick interior it would easily be possible to build a draft door with moveable slides or slots with which to control the amount of draft. A possible scenario of after an hour's firing one could increase the draft from a gentle breath of extra air flow to something more vigorous that would significantly shorten the clearing time might be considered. It would be an interesting experiment with a WFO having thermocouples built in to see how much the heat transfer would be increased (and thus time to clear shortened) using such a draft door.

The idea of firing for three hours to first pizza would be a put off for me with an WFO I built for pizza as a primary use. While a three hour firing of a WFO designed for principle use of baking several loadings of bread however, would not be unacceptable.

Thanks ,
Wiley

[Bravo]

Re: How long to get to temperature?

As for drying the wood, 500 degrees will be too hot and you will find ash in the morning. All i do is check temps and put wood in there. The subsequent fire is hot and fast.