#11  
Old 06-08-2008, 01:19 AM
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Default Re: Blacksmithing and WFOs

Just one thought that sprang to mind reading these posts.... isn't it better to heat the dome up more or less slowly? In theory you don't want to get it burning white too fast, because of the additional thermal stress this causes. I think...

That said, the gentle breeze blower does sound like a good idea.

Talk some more about this other coating product though. Seems to me that plywood experiment means that the wood would start burning after 20 minutes anyway... what gasses would those have been causing the paint to bubble? How durable is the product amd how much covering does it give? Is it anything like regular paint?

Sounds really interesting.... you could make your door out of whatever material you want. Or just coat a sheet of metal... how well would that insulate with the paint on?

Anyway, you'd definately want the coating on the outside of the dome, NOT the inside, otherwise the bricks wouldn't be able to absorb any heat. And you'd probably want to check for toxicity (is that a word?) even for the outside, the firebricks being quite absorbant and all.
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  #12  
Old 06-08-2008, 04:42 AM
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Thumbs up Re: Blacksmithing and WFOs

One experiences different degrees of sucess when setting and lighting fires in their WFO. I have adopted to use 2 X 3 legged steel supports that I screw up paper and put under the bar which is around 2" parallel to the floor. Over the steel link between the 3 legs, I lay the kindling and the small wood, light it and apply a gentle breeze using the pertol powered garden leaf blower BUT I stand back around 2-3 metres letting it idle and aim it at the bottom of the oven door. Within 10 to 30 seconds, the fire is absolutely roaring, needing more and larger wood.
So the extra air certainly works and especially when things are a little slower than required. I have found that the wood needs to be raised or at least propped up), and an extra draught certainly gets the fire going harder quicker.
I now plan from reading this thread, is to set up a sheet of steel (thin iron sheeting) around 2" off the floor and running through the door almost to the fire edge. This would reduce the friction between the escaping hot air from the cool entering the oven. I will make a baffle which will also deflect the air around the fire to supply the 'back of the fire' rather than just the front. No fans nor forced air, just fanned by natural convection currents.
I have a large pizza cookup tomorrow and will post some pics and report on its success or failure.

Neill
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  #13  
Old 06-08-2008, 05:38 AM
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Thumbs up Re: Blacksmithing and WFOs

I just went out into the workshop and made a prototype in 15 minutes. Got a sheet of steel, drilled 3 holes in it and screwed 3 offcits of 25 x 28mm tubing offcuts in place.
The longer ones can be rotated to direct cool air to the sides and around to the back if the fire. In doing this, the air which would go to the front of the fir is restricted because of the angle of the supports/baffles. When they are parallel to each other, more air will be directed to the front of the fire and less to the sides and/or back.
The third pic is with the plate sat in the doorway just in front of the 2 tripod stands that I use to prop up the wood encouraging more air to get the fire going easier, better and consequently hotter.
I will use it tomorrow and play with the two front baffles and take some pics for show and tell tomorrow night.
Wish me well, till then,

Neill
Attached Thumbnails
Blacksmithing and WFOs-air-back-web.jpg   Blacksmithing and WFOs-air-front-web.jpg   Blacksmithing and WFOs-plate-oven-doorway.jpg  
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  #14  
Old 06-08-2008, 10:29 AM
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Default Re: Blacksmithing and WFOs

Quote:
Originally Posted by Frances View Post
Talk some more about this other coating product though. Seems to me that plywood experiment means that the wood would start burning after 20 minutes anyway... what gasses would those have been causing the paint to bubble? How durable is the product amd how much covering does it give? Is it anything like regular paint?

Sounds really interesting.... you could make your door out of whatever material you want. Or just coat a sheet of metal... how well would that insulate with the paint on?

Anyway, you'd definately want the coating on the outside of the dome, NOT the inside, otherwise the bricks wouldn't be able to absorb any heat. And you'd probably want to check for toxicity (is that a word?) even for the outside, the firebricks being quite absorbant and all.
Frances, this sounds like a product I encountered back at an exposition of home building materials and stuff back in 1982 in when I lived in Paris. The guy in the booth had all they small samples of plywood coated with this paint on one side. He would speak his spiel as he was playing a propane torch against one side of the sample. Periodically he would set down the torch and hold his hand against the back of the sample and then offer to someone in the crowd to feel how hot it felt. The paint would puff up and blister getting thicker and thicker the longer the held the torch flame against the sample. I was very impressed. They were pushing the product for painting apartments as an undercoat to keep fire from spreading as fast in a building. If I remember correctly the amount of protection depended upon the thickness (read that number of coats) of the paint. I was redoing my girl friend's apartment and thought this was something we should do. I was over ruled as the stuff wasn't inexpensive and that was that.

I could never find the product in the US when I returned home. I wanted to paint the inside of the engine compartment of my boat (my residence for 11 years). A fire in a home is very bad news and a fire at sea....

Anybody know if this product is available in the US?

Wiley
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  #15  
Old 06-09-2008, 02:19 AM
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Thumbs up Re: Blacksmithing and WFOs

Report as promised.
It was up at first light and breakfast before making 3 batches of pizza dough mix and one spicy fruit mix. At around 9:30am, I set and lit the oven fire whilst trying to clean up the patio after the overnight rain. As I didn't have a great deal of time to tend the fire (which I have found in the past is almost a necessity) and I had a roaring fire with the prototype air-chute/draught controller in place within a half hour. Two hours later, the oven was over 500˚C (as the infra-red thermometer max'd out). I had to let the oven cool down before I could show our guests who were new to WFO's the procedures for preparing and cooking their own special pizzas.
I noted that I could put on the largest sized wood that I normally used much earlier as the fire was much hotter and burning harder with the unit in place.
I removed it an hour before cooking, mainly to allow the oven to cool a little.
Next alteration, well I will probably wait until I have the new patio roof up and the power run to adjacent to the oven. I plan on making a new draught controller with a 12v heater fan attached and a variable speed controller to force induction the air to meet the oven's needs. No new equipment needed but a couple of hours time and then continual use when lighting the fire.
I will post a new thread once I am at this point.
Stay tuned.

Neill
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  #16  
Old 06-09-2008, 08:06 AM
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Default Re: Blacksmithing and WFOs

Just reading this thread makes me realize why most folks do not cook with WFOs anymore......smart engineer types are always trying to innovate to make things go faster and easier. Crack me up! One reason I like the WFO is that it is low-tech. Its slows me down to work at the oven's pace. Part of the fun is that it isn't fast. I am not being critical just observant. Day in and day out I am thankful to turn a knob on in my inside oven and know what temp and how long things need to cook. Keep up the innovation, but don't lose site of the joys of the slow cook!
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  #17  
Old 06-09-2008, 08:39 AM
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Default Re: Blacksmithing and WFOs

krosskraft brings up great points.

These same concepts run throughout the blacksmithing and woodworking communities as well (and probably almost all "old timey" hobbies).

The cob people look at our high tech refractories and roll their eyes. propane blacksmiths vs coal vs charcoal. Power tool woodworkers vs handtool guys.

And then we have ALL of us typing on computers to be in this community.

I'm starting to narrow it down. I think that people pick an aspect (or several) that they want to remain "as it was", and then they don't mind things progressing in other areas.

Some guys are about the process, wanting that part to remain "as it was in the olden days". Very admirable.

Other guys are about the tools, the construction.

Others, the product. Bread and pizzas just like they had it.

You can see how it begins to spawn different end results in both ovens and products and processes.

It's all fascinating to me.

I think on some level, all of us here would dislike the Jetson's "push a button and out comes the food" type of life, but as to where each of us make our "connections" with the food being created, it varies wildly.

I love your observations.
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  #18  
Old 06-09-2008, 08:47 AM
Peasant
 
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Default Re: Blacksmithing and WFOs

Neil,

Interesting results with your "fresh air intake".

One of the upsides to a pompei over a barrel is less thermal mass = less time to heat = less fuel used.

The downsides to less thermal mass include shorter window of high temperature without adding more heat, and for the bread/fireless cooks - less bread may be cooked, and for the 36hours after I cooked a whole hog people - food poisoning.

BUT, all things being basically equal, I think people wouldn't either minding the oven not taking quite as long to heat up, OR it takes the same time, but has more thermal mass to allow them higher heats or longer cooking, etc.

It's the reason we all use bricks at all instead of just a steel shell.

I like the low tech, low intrusion methods. I'm pondering the possibility of plumbing in some air chambers that would allow air be drawn in through the floor such that you could cut off the supply when the fire was moved or the air otherwise not needed.
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  #19  
Old 06-09-2008, 08:51 AM
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Default Re: Blacksmithing and WFOs

I agree as well. One of my hobbies is photography, and I'm one of the few people who still use only film. Even for snapshots of family and friends I'm using the film camera. I'll take a picture and people who don't know will say "let me see it." Not too much patience anymore for lots of stuff. I actually develop and print my photos as well. Its about the process as well as the materials for me. Shoot, I still use a few view cameras..you know the box ones where you have to get under the dark cloth to see through.
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  #20  
Old 06-09-2008, 08:51 AM
Peasant
 
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Default Re: Blacksmithing and WFOs

I assume the bricks obtain their heat through both radiant means and conduction from the hot air/other bricks.

Do we know which of these two is primary?

If the primary way the heat is added to the bricks is by conduction, I can see the ITC coating being helpful on the inside of the dome as it makes the bricks even more reflective than they were before.

If radiant is the primary, I can't see the ITC being helpful on the inside, because it would slow the heat absorbtion. At blacksmithing temps, there is more radiant transfer going on, but I don't know if that changes at these "lower" temperatures or if it's the same.

Anyone?

PS I know there are lots and lots of microthreads in this thread. Sorry about that.
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