The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

WFO "Outer Door"

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MNBäcker's picture
MNBäcker

WFO "Outer Door"

So, I did finally get around to building my "outer door".  Most of our ovens are heavily insulated on 5 of the six sides, but the front, for practical reasons, does usually appear somewhat "exposed". I use my oven once a week to bake about 140 loaves for the local Farmer's Market. My objective was to keep as much heat as possible in the oven between my weekly bakes. I had my local welding shop make me a metal plate that would be big enough to cover the exposed front of the oven. The edges are bent in for 2 inches, to support the insulation and keep the welding blanket from wearing through over a sharp edge. I filled it with 4 inches of high-heat insulation and left an "indentation" for the handle of the door (since my door is very well insulated with Foamglas, it stays in place when not baking). I covered the insulation with a welding blanket and screwed that welding blanket onto the edge (think large chair cushion). A couple of handles to lift it in and out of the chimney opening, and we're good to go. After baking, I set it in place and push it as closely as I can to the oven wall (it makes contact with the wall on the top). I don't have any good numbers yet, since I am still changing my firings with the increased demands in terms of number of loaves and the amount of heat I need in the outer layers, but I think I can tell it makes a difference. How much, remains to be seen, but once I fire my oven more consistently I can take some better readings and compare them to a week without having the outer door on.

A view from the side - roughly 4 inches thick.

 

View from the front with the two handles. The gunk in the middle is soot coming down from the chimney when we have a good downpour (that's WITH a raincap!).

 

And here the outer door is in place. I had an internal temp of 475 after I was done baking on Monday morning at 4:00am. Right now, Friday night at 7:00pm, it's at 235 degrees.

 

Stephan

www.firebrickbread.com

 

PMcCool's picture
PMcCool

Stephan,

I saw your post on the Yahoo Brick Ovens group but didn't realize (until I saw this post) that you are also MNBacker here on TFL.  

You have a nice setup with your oven and it appears that your outer door is effective.

Paul

MNBäcker's picture
MNBäcker

Yeah, Paul - sorry for the cross-post. I figured there might be some overlap...

When I take the outer door off, I can definitely feel some warmth on the outside of the front bricks. I'm pretty sure the door is doing SOMETHING - how much exactly, I hope to find out in the next few weeks.

Stephan

www.firebrickbread.com

 

PMcCool's picture
PMcCool

There are people on each forum who don't participate in the other, so you get better coverage by posting in both.

Paul

JerryC's picture
JerryC

I like what you did with your door. I have a W F O and have a sheet metal door that is mostly used to keep critters from building a home in there. I use my oven for making pizza and it works great, but I will need aninsulated door when I start making bread. I think I will follow your example and use some of theceramic fiber insulation I have leftover and cover it with welding cloth fastened with screws. I saw some carbon fibre stuffthat looks good and is not too extra agent if I can use the 18" square. I have some measuring and calculating to do yet.

MNBäcker's picture
MNBäcker

Jerry,

just to clarify: the "outer door" is in place IN ADDITION to the regular oven door (which is sheet metal filled with Foamglas) when I am not baking. I would imagine that the welding blanket would withstand the heat of the oven (they're usually rated to 1,000 degrees), but you would want to make sure to keep the door away from any flames and/or glowing embers.

Let me know how it turns out for you!

Stephan

JerryC's picture
JerryC

That won't be a problem. When there is fire in the oven the door is not used. When it's time to bake bread, the fire and ashes are removed and the deck wiped with a dampmop, then in goes the bread and on goes the door. The oven temp should be 500 to 600 degrees at that time.

MarkUK's picture
MarkUK

Just a couple of thoughts re insulating brick ovens:

Contrary to a lot of folks thoughts, clay, brick and cement are lousy insulators, there is a tendancy to belive that very thick walls in old cottages etc are there because its good insulation. True the thicker a materail is, the better it will insulate. One of the reasons why we use brick ovens (or thick walls) is that they are very good at storing heat and maintain (once heated) a more even temperature. Hence one of the advantages of inglenook type fireplaces.

It therefore makes good sense to insulate an oven if it is not being used continuaously as it takes a lot of heat to bring a cold oven up to temperature. The key thing is to make sure all the insulation is joined up with no gaps, and don't forget the base as 30-40% can be lost this way. If an insualted door does not butt up to the insulation, then a disproportionate amount of heat can be lost this way, which is a shame after all the effort. In building terms it is called "cold-bridging" and even builders don't always appreciate how critical this is. The other option if insulation cannot meet is a good overlap, but this is not so feasible with ovens.