Buckley Rumford Fireplaces
Massie 36" Oven and 48" Rumford
The Building Experience

Great description of first fire and pizza

Pictures from Massie's blog*

From: "Thomas Massie"
To: "Jim Buckley"
Subject: Adding thermal mass to the 36" bread oven?
Date: Tue, 25 Dec 2007

Jim,

Here's the peel company: http://www.lillsun.com/about_us.htm

Looks like one of the few USA mom-and-pop manufacturing businesses in this country that haven't been put out of business by the Chinese machine. Perhaps you could be a distributor for them? I see you sell a nice forged steel peel. This might be a good compliment to the product line. It is priced very low, so there might not be enough margin to make it worth your while (or enough volume on your end to make it worth their while). But hey, get one for yourself if nothing else!

I ordered ours retail through http://www.globeequipment.com/Catalog/LIL!124228.html I am impressed with the lightness of it and although it is not advertised as such, I'm pretty darn sure that it is basswood (a.k.a. american linden tree). Although not explicitly stated, the overall length of this model is 42".

Perlite: Perhaps you already have this information, but if not, I think you'll find it useful. Real engineering numbers for Perlite mixed with cement. If you have other sources of similar info, I'd be interested in that as well. I'm using about 1.5 to 2" of the Delta-Crete Castable Refractory Insulation that you distribute (i.e. 6 bags for a 36" oven), with an additional layer (3.5" avg.) of Perlite and Portland outside of that. Might loose-fill some perlite above everything as well.

Here's the link:

http://www.perlite.org/perlite_info/guides/lightweight_insulating_concrete/general/perlite_concrete.pdf

Happy new year!
-Thomas

    ----- Original Message -----
    From: Jim Buckley
    To: Thomas Massie
    Sent: Sunday, December 23, 2007
    Subject: Re: adding thermal mass to the 36" bread oven?

    Thanks, Thomas. I would like the name of the peel mfg.

    Merry Christmas,
    Jim

Thanks for the quick and thorough reply... the mason that's helping me basically said the same thing (without the theory) today "doesn't matter what size it is... its the draw that matters." We laid the brick hearth and the oven segments today. I will send you some more pics soon.

Yes, I'll be able to block off all air flow through that could come thru the ash dump. If the oven works fine without it, I'll just call it an ash dump instead of air makeup!

Speaking of happy holidays, I bought my wife a basswood pizza peel for Christmas. Made in Indiana and cost less than $20. I will send you the mfg's name and address next time I send pics. Merry Christmas.

-Thomas

    ----- Original Message -----
    From: Jim Buckley
    To: Thomas Massie
    Sent: Saturday, December 22, 2007
    Subject: Re: adding thermal mass to the 36" bread oven?

    Thomas,

    Thanks for the progress report and picture. The taller the chimney the better the draft. Its a linear relationship so that a 20 foot tall chimney creates twice the pressure differential at the throat as a ten foot chimney would. And it's the height that matters - not the cross-sectional area - as long as it's big enough. The 8"x8" flue would draw only slightly better than the 4"x8" flue because the flow speed and therefore the frictional drag would be less. But you wouldn't notice it and the 4"x8" would already draw very well because it's so tall.

    A well designed oven shouldn't need make-up air although a little extra air is often a "fix" for an oven that doesn't work very well. The ash dump might be handy. I would just make sure you can close off the extra air if you don't need it. It might make the oven cool off sooner.

    Keep me posted and send more pictures.

    Happy holidays,
    Jim Buckley

Jim,

I had to put my fireplace/pizza oven project on hold last spring, but now I'm back in the thick of it (and having fun). I am documenting the build on my blog http://massiehouse.blogspot.com. Just to recap, I'm building a 48" rumford (your kit), a wood cookstove, and a 36" pizza oven (your kit) into one masonry structure.

I have one important question for you... from the top of the pizza oven to the point of exit (top of chimney), my pizza oven flue will be 29 feet tall. I am pondering whether these 4x8 flue liners are really big enough, given the length of the flue. I'm not sure whether the extra height will improve or restrict draft, such that a different flue liner might be advised. For instance, my wood cookstove (the old fashioned kind) has a 6" round flue that goes into an 8x8 clay flue liner while the Rumford as you know has a 16x20 flue liner. If it is relevant, I should also mention that I have made provisions for fresh-air-make-up/ash-dump in the back of the pizza oven. If it were true that bigger is always better, I would upsize the flue to 8x8, but I am worried that too large of a flue could cause unforeseen issues. Thoughts?

Thanks for any insight you might have,

Thomas Massie

    ----- Original Message -----
    From: Jim Buckley
    To: Thomas Massie
    Sent: Wednesday, April 04, 2007
    Subject: Re: adding thermal mass to the 36" bread oven?

    Thomas,

    Glad to hear that so far you've had a good experience with our dealers. I look forward to seeing pictures of your project.

    Interesting that you mention your experience with formed concrete. I think that's a fine way to build fireplace and chimney enclosures. See http://www.rumford.com/concrete.html

    As for the thermal mass around the oven, I think your plan will result in too much mass. With our two to three inch thick linings, surrounded by the insulating refractory concrete (which has both mass and insulation) plus more insulation all inside some finished enclosure you will have an oven that should heat up in about two hours and stay hot that long or longer depending on how much extra insulation you have around the insulating refractory concrete. The extra layer or brick around the oven and the thicker firebrick hearth will make the oven heat up and cool down slower. Either way the more insulation around the outside the better.

    We have had few complaints but some of our customers report that it takes hours and hours for the oven to heat up - usually because they didn't have any or enough insulation around the oven or between the oven and the surrounding masonry mass of a big fireplace and chimney.

    Thanks for the link to your blog.

    Best,
    Jim Buckley

Dear Mr. Buckley,

I have purchased both the 48" rumford kit and the 36" bread oven kit (and associated flue liners) from Superior Clay, through a distributor called "Standard Supply" in Maysville, KY. It has been a pleasure dealing with them -- the materials have arrived promptly and in perfect condition. I have also found your website to be a wealth of information. I have read the website extensively, and recently purchased the book "The Bread Builders".

I will soon be ready to begin work on my fireplace and bread oven. Within a single masonry structure, I will have a Rumford fireplace, a bread oven, and an alcove for a wood cookstove. Eventually the structure will be faced with 4 to 6" of siltstone. I readily admit that I am no mason, but I do have some formed concrete experience (we poured our own 2200 sq. ft. basement, as well as a 38 ft long bridge and abutments). Part of the mass of the chimney will inevitably be directly above the back of the pizza oven, the throat of the rumford, and the alcove for the woodstove. Therefore, I think I will form, place rebar, and pour the first 8 feet of the masonry structure, and begin blockwork for the chimney from there.

It is likely that I will have a few more questions, but today I am writing you for your current thinking on what is the ideal thermal mass for the bread oven. Specifically, I am considering adding some firebrick directly to the outside surface of the white refractory dome, and turning the hearth firebricks on edge in order to effectively double the thermal mass of the the oven. I may also add a proportional amount of extra "insulating castable" or perhaps some other insulation. Do you have any feedback, annecdotal or otherwise, from users of your 36" ovens that have and have not added extra thermal mass? Firing times and/or cooking times? For our residential application, it would be nice to keep the firing times below 1hr30mins, and to have at least two bake cycles for bread (w/o fire) after doing pizzas (w/fire). Is this possible with the kit as-is, or do you think I might benefit from adding a little more mass?

Thank you in advance.
Sincerely,
Thomas Massie

ps. I plan to document the construction of both the bread oven and rumford fireplace on my timber frame house blog. I have included a link to that site below.

http://massiehouse.blogspot.com

Superior Clay Bake Ovens
Buckley Rumford Fireplaces
Copyright 1996 - 2009 Jim Buckley
All rights reserved.
webmaster