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Groves 06-07-2008 06:15 AM

Blacksmithing and WFOs
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 06-07-2008 06:40 AM

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. :D

ITC-100 coating

Can you give me some more info on this material?

Where can it be purchased?

How expensive is it?

CajunKnight 06-07-2008 06:49 AM

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

ITC-100 OSHA Material Data Safety Sheet (front) :

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 06-07-2008 07:07 AM

Re: Blacksmithing and WFOs
Couldnt stop there

ITC Ceramic Coatings at

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 06-07-2008 07:49 AM

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 06-07-2008 08:01 AM

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 -

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 06-07-2008 08:49 AM

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.


Wiley 06-07-2008 09:17 AM

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?


Groves 06-07-2008 09:25 AM

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 06-07-2008 01:47 PM

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.

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