Blacksmithing and WFOs

[Groves]

Just taking it all in, folks.

One of my other side hobbies is to bang some hot metal now and again. There are many similarities between your WFO designs and the design of a good forge.

I began to think of cross-over ideas, and wondered whether ideas that help out in the blacksmith forge world would work in this world, too.

"Oven" temperatures are much higher in blacksmithing, so they're obviously worried about the same kinds of things that you guys are. Efficiency, thermal mass, etc.

I'd like you guys to consider these ideas from the WFO side and give me your opinions. Here are two.

#1 Use a blower

Although we often think of fuel for a blacksmith being coal, the reality is that charcoal worked perfectly fine for thousands of years. Coal is relatively recent. You can use charcoal to get iron out of ore (at 2600F) or just heating up iron enough to be worked (1600F) quite easily.

Since the main part of WFO cooking is loading whatever thermal mass you have, why not use a blower to make the fire hotter sooner?

I realize that the heat will still take some time to saturate all of the firebrick, but why not have a fire that's several hundred degrees hotter doing the job?

You can shut it off anytime you want, and for pizzas, I assume most will still want a fire inside during cooking.


#2 ITC-100 coating

There are several types of forges in use today, but all of them benefit from maximizing the reflective heat inside the chamber. For the most part, blacksmiths don't care about having thermal mass, as an excess simply requires more heat/fire/fuel to bring the forge up to working temperature.

In a modern propane fueled forge, for instance, you'd really like to cut the thermal mass down to as little as possible. Think of it as a WFO without the firebrick. Mostly ceramic wool insulation inside a steel shell.

Losses through radiation are extreme at these temperatures, so they apply a coating to the wool to both protect it somewhat, and significantly increase the reflectivity of the surface. A product called ITC-100 is one of the popular thermal ceramic coatings used.

I don't know how it would react with dough, but what about coating the dome to increase reflectivity?

Just some thoughts. Loving the site.

[CajunKnight]

Re: Blacksmithing and WFOs

Hi Groves, welcome to the site. You have an interesting idea there. The use of feeding more air to get more heat is one I have been toying with myself. Once an oven is properly cured I think it would help a lot. I have heard it mentioned where some were using air to assist in getting fire going but none in building heat. Then again there is so much info on this site I could have missed it. The two ideas I am considering are as follows. A 4" squirrel cage blower ducted directly into the door close to the base of the fire with a damper to adjust airflow. This can be removed after white dome is reached. The other idea is using low pressure air from an air compressor. A regulator to adjust flow and also can be removed when white dome is reached. Again I would do it until after a proper slow cure was done on the oven. I think I would have to bring it to heat a few times before doing it also. I think its an idea worth looking into. Then again I am no expert so lets hear it from the old timers here.


ITC-100 coating

Can you give me some more info on this material?

Where can it be purchased?

How expensive is it?

[CajunKnight]

Re: Blacksmithing and WFOs

OK I couldnt wait...

One site available from
ITC-100 HT : High temperature ceramic coating for refractory brick, castable, blanket and board

MSDS
ITC-100 OSHA Material Data Safety Sheet (front) : anvilfire.com

Next question, since its a reflective surface and the idea of a WFO is to retain heat in dome brick should this be applied inside dome or would it be better suited outside dome before insulation is applied? More info to dig into lol. I love it.

[CajunKnight]

Re: Blacksmithing and WFOs

Couldnt stop there

ITC Ceramic Coatings at Axner.com

The more I read I think it would be better suited in the outside of brick before insulation. It would also make one heck of a covering for a wooden door.

quote from this site:
Even Combustible Materials Such As Wood Are Able to Withstand High Temperatures When Coated With ITC Products
Nils coated a 3/4 inch piece of plywood with ITC coating and used it to cover the main stoking port of his anagama kiln as cone 14 was bending. After 10 minutes the back of the board was still cool. After 20 minutes it was removed revealing gases had bubbled the coating and it was only then beginning to burn. WOW. How about a disposable kiln made from ITC covered plywood? NOTE: Don’t try this at home.

OK correct me if I am wrong. Seems that if I pour hearth slab and apply perlcrete then coat with ITC 100, this should reduce heat at insulation layer and reflect heat back into the cooking floor. Just reading about the wood amazed me a bit.

Now another question. What is cone 14 in degrees?

Hey lookie I am using edit again. I didnt find what cone 14 was but cone 13 is around 2500 degrees F. This could be new life for a wooden door.

[Groves]

Re: Blacksmithing and WFOs

Just to clarify, I'm talking about adding air to a wood fire, not turning a WFO into a PFO.

A squirrel cage is just too much air, usually. It's common for people to think squirrel cage and vacuum cleaner when they think of blacksmith blowers, but it's much much less air that we're after. Even with a damper it's best to find either a really small squirrel cage or a blower from a copier or similar machine.

The perfect solution is a small child and a simple hand crank blower, not that I need or desire any more competition for the decreasing supply of old blowers, either.

[Groves]

Re: Blacksmithing and WFOs

Here's a chart of different ITC products

ITC Problem Solving and Application Chart: ITC-100 HT, ITC-148,ITC-200, ITC-213, ITC-296A sold by Dempsey's Forge - anvilfire.com

We tend to use Kaowool as an insulating blanket, but I wonder how it compares to the ceramic blankets you guys use.

Maybe the only difference is the temperatures it can operate at, but there could be some R-value and/or price differences, too.

[asudavew]

Re: Blacksmithing and WFOs

I've tried a compressor, a fan, a venturi burner... etc. etc.

I've even used two venturi burners.

So much mass to heat... it would take days... I always ended up building a fire


I don't mess with any of that stuff anymore. Wood is the way to go.

My 2 cents.

Dave

[Wiley]

Re: Blacksmithing and WFOs

Welcome Groves,
Kaowool is most likely the same product by a different name. I am familiar with kaowool thru glass working where a common name for it is Frax. From descriptions and photos here of looking like cotton batting and the color of flour I think it's the same. It is also available as a thinner product that is compressed and used for slumping glass over, it looks like felt (Frax paper).

As for introducing more air for better starting and combustion, I sort of wish I hadn't taken down my test fire setup for my steel dome oven. To me, dmun's photo yesterday of the fireplace cover with adjustable air slot is to me the best idea going. I first encountered restricting airflow to a fireplace by means of a sheet of newspaper many years ago and if my test fire setup was still assembled I would like to try it. Simply start your kindling and spread a sheet of newspaper (open) across the entrance. Grasp the center bottom of the sheet and slightly lift so as to cause a small opening. The effect is like someone continously blowing on the fire and one can control the speed by either increasing or decreasing the size of the opening. There might be some problem with the fact that the fire on a WFO is so far back and the chimney opening is closer to the lifted edge than the fire is. But I am most anxious to see if it works. Anyone having a WFO and starting a fire this weekend willing to give it a try and report back?

Wiley

[Groves]

Re: Blacksmithing and WFOs

I see all sorts of pictures of guys "augmenting" their fires with propane torches/weed burners, so I'm sure there's interest in a faster/hotter flame.

I'm not talking about propane, though, just air to a wood fire.

It would be a tradeoff using more fuel (probably) for a quicker heat.

You can stick steel in a wood fire all day*long and not get it beyond dull cherry red, but add some more oxygen (i.e. air) to that same fire and you can be at a white hot heat in no time.

A gentle breeze will do wonders, and a hard blast of air will be horrible.

I'm not sure that plumbing an air source is the best method. If you plumb it, then your staring fire must always be in the same spot.

If you stick something through the front opening instead, then it's less convenient.

All trade offs.

[CajunKnight]

Re: Blacksmithing and WFOs

I should have been a bit clearer lol, the squirrel cage I have is actually a computer server cooling fan. It delivers a gentle breeze without a lot of force. It was from an older system before they started using the fans we see in computers now.

[Frances]

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.

[nissanneill]

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

[nissanneill]

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

[Wiley]

Re: Blacksmithing and WFOs

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

[nissanneill]

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