Colorado oven

[ThisOldGarageNJ]

Re: Colorado oven

Great Idea,
I am a seat of the pants kinda guy, and what your saying makes a lot of sense to me. Once you reach equilibrium, you should be golden..

BTW I cured by the 7 day fire schedule after 28 days of air curing, (heat stop 50) to date I dont have a crack that I have seen inside or out,

There are so many variables in oven builds, mortar mixes, bricks and materials etc,, I think wheather or not your oven cracks couldnt possibly be answered definitvely.. We all do the best we can and hope for the best and hopefully learn from the misteaks others have posted and shared with us,, I am far from an expert and think I just got lucky with the right combination of things, and Voila no cracks (theres still time)
Mark

[drseward]

Re: Colorado oven

I think you are exactly right. If my oven doesn't crack, there are too many variables to attribute it to my curing technique. Perhaps if it does crack, that will be more telling.

Mark

[brokencookie]

Re: Colorado oven

I appreciate all the comments.


I see two potential problems. First, the formation of steam could damage the structure. Second is the temperature differential that would exist in an oven mass heated above the boiling point of water with water still present. For instance, dry areas of the oven could heat up to many hundred degrees F while areas with retained moisture could not exceed the boiling point of water. That could create significant thermal stresses to the structure.

I think you are exactly right. I run the laboratory for an oil refinery. Without getting too technical, fractional distillation is the backbone of refining. Simply put, liquids turn into vapor at a specific tempertuare.
When we distill a crude oil that contains water, we have to hold the temp at about 98.5 C ( 195 F) until all of the water has turned to vapor. Only then can we raise the temperture.
When water turns to steam it expands to about 300 times it's liquid volume. When we do this too rapidly in a distillation column it fountains crude oil out the top. This is also why you do not put out a kitchen grease fire with water. You will end up cleaning it off the ceiling.
By maintaining that low temp until the outer temp reaches the boiling point of water you should be able to slowing release the trapped water without a sudden surge in pressure as the water expands.
As another thought, the mortar may look dry but is is really not. The dryer it becomes the harder it is. Some of the cracks that appear may be from the mortar being slightly wet and therefore weaker when the initial expansion and contraction stresses occur.

Just my 5 cents ( adjusted for inflation)

Bruce

[testadom]

Re: Colorado oven

All I can say is, WOW!

[Ryan]

Re: Colorado oven

That dome looks perfect! Great work!

[DrakeRemoray]

Re: Colorado oven

I don't think we have done a "best of the month" in a while, but I sure nominate this oven!

[MumsOven]

Re: Colorado oven

Nice brickwork Mark, Love the attention to detail

I cured my oven using just wood fires however I just kept the fire quite small - tried to maintain low temperatures for long period of time (days) then increased the fire size (more days) & so on. After about 3-4 weekends when I felt all the moisture had gone, I used the oven for cooking casseroles, roast's etc 160 - 200C for several days then fired to around 500C - to date no cracking in the dome, 1 hairline crack in arch.

[michaewa]

Re: Colorado oven

Mark - How far from the true center of the dome was the base of the arm? I like the resulting dimensions of your dome a lot, and am getting ready to cobble together a similar guide.

[drseward]

Re: Colorado oven

I don't recall how far off center the arm hinge was. I just determined the placement on site while building the oven.

I made the lenth of the arm so that the top of the dome was the height I wanted (the finished dome height minus the thickness of the lazy susan, plywood based, etc.).

I then set the soldier course and fastened the arm hinge on the turntable so a brick held in the clamp was positioned properly on the soldier course. You could certainly draw it out and determine the position, but I found it easier to determine the placement in place.

Does that make sense?

Mark

[michaewa]

Re: Colorado oven

Mark - it does, thanks very much. I'm in a bit of analysis paralysis at the moment, I think I just need to start going.

One other question regarding the tool - how did you attach the rod to the hinge? Was that a weld or some combination of off the shelf parts. I can't quite tell from the pics.

Your oven looks fantastic, and I really like your curing logic as well. The firing schedule seemed a bit haphazard to me as well.

Cheers,

Andy

[drseward]

Re: Colorado oven

Andy,

I just drilled two holes through the end of the threaded rod and attached it to one plate of the hinge with small bolts (I ground the rod threads a bit flat where they met the hinge plate). That was easiest for me.

I'll be anxious to see how your build goes.

Mark

[fxpose]

Re: Colorado oven

I think you can roughly determine how far off center to place the hinge by taking:

(radius of oven) minus (dome height or arm length, less thickness of base mount) = distance off center

[michaewa]

Re: Colorado oven

Mark -

Your suggestion on the indispensible tool was great. My dome doesn't look nearly as nice as yours but it has the correct dimensions, 42" with a 19" high flat(ish) plug in the top.

I'm going to do the vent transition soon, and was hoping I could impose on you to take a picture underneath your vent? I would like to see how you transitioned from the brick to the castable.

Thanks!

Andy

[drseward]

Re: Colorado oven

Hi Andy,

I don't have the photo you asked for. Now it's a black hole up there and would be impossible to see much in a photo. Here is a side photo that may provide some additional information to help out. The inside of the poured transition mirrors the external profile, so the slanted part of the transition is of even thickness. Does that make sense?

You may also be able to see that I made the outer arches completely detached from the inner arch and dome. From the inside, the entry is butt up against the inner arch. However, from the outside you can see there is about 0.75 in. gap between the entry and the inner arch. I packed this with insulation and it created a good heat brake between the oven proper and the entry. That worked out very well.

Let me know if I can do a better job of explaining anything.

Mark

[michaewa]

Re: Colorado oven

Mark - fantastic! Thank you very much! I may be past the point of leaving the gap between the outer arch and the dome, but I love that idea. Thanks again for the fast response - I hope to be cooking pizza within the next few weeks...