Caribbean Wood Fired Oven

[stonecutter]

I’m all ears for some ideas for a castable mix design.

[UtahBeehiver]

DavidS is our resident casting expert. Since fire clay is not available maybe a commercially made dense casting refractory would be best since you may have to import anyway. At least importing of the floor firebricks would not be a numerous as the complete oven. I am sure David will chime in.

[david s]

If access to clay is not available you could dig for your own. There is usually a layer of clay beneath the topsoil. If there are any building sites nearby get in when they are digging for the footings. You need to dry it, break it into fist sized lumps, soak it for a few days, then dive out coarse material, dry it and pulverise it to a powder. Alternatively make a cob oven with far less processing of the material.

[stonecutter]

Funny you mentioned that David. There’s clay everywhere on the island and lots of handmade Hornos that are used by the locals. I was going to test out some soil at my house and I just may go the clay oven route just for fun. Do you have any suggestions for a mix design? I’m thinking I’d even cast floor tile as well

[david s]

In my job as an art teacher, I’ve frequently processed small amounts of clay as a demonstration about clay’s origin. It produces a surprisingly consistent and workable clay with good characteristics. If using it for a cob oven you do not need to go through the same kind of processing with fine sieves though. The mix should be 2 parts sand for every one part clay by volume. Don’t worry too much if a fair proportion of it appears looking more like topsoil, it’ll still work ok. You need to allow the clay to dry completely so it will take up the water. It should also be then broken up into lumps no bigger than a fist. An easy way to make the mix is to get a large sheet of plastic, mix the dry sand and clay together then add water slowly whilst mixing by stomping with boots or bare feet. Occasionally lift the corners of the plastic to get the mix back in the middle. Normally chopped straw is added during this mixing stage. This can be a fun activity if combined with female company and alcohol.

[stonecutter]

Hey guys, hope everyone is doing well in spite of the conditions. So here’s where I’m at right now: I had harvested probably 30-40 lbs of clay...maybe more I don’t know...intending to cast an oven. About a month ago, I stumbled across a source for locally made clay brick, made in the same manner has the ones they use in Italy. They only cost HNL 9.00 each and it takes 24.68 HNL to make a dollar. So I bought 200 so I’d have more than enough to play around with. As usual, we have tons of other project ahead of the oven but I’ll be starting it soon. I ordered a ceramic blanket and I’ll have to order double wall chimney pipe too, but that won’t hold me up.

[Chach]

That's a hell of a deal! Like $0.37 each....

[UtahBeehiver]

StoneCutter,

Good to see you are still checking out the blog. Didn't you move to a Bermuda or some place like that? Looking forward to seeing number 2 oven.

[stonecutter]

StoneCutter,

Good to see you are still checking out the blog. Didn't you move to a Bermuda or some place like that? Looking forward to seeing number 2 oven.

Hey Russ, I pop in every once in a while. We moved to the Caribbean over 4 years ago, first to ambergris caye in Belize. We didn’t like how small it was so we moved to Roatan about 2.5 years ago. This oven should get rolling soon but for now I need to keep an eye on a possible hurricane. Btw, this one is only number 2 that I’ve documented on the forum..I’ve built many others. How is your garden this year?

[stonecutter]

Well, the lack of content explains the fact this oven never got off the ground. We had several hurricanes to deal with that year and we completely remodeled the first floor apartments,so that ate up all my time. We moved back to New York March ‘21 and I’m currently gathering stone for the the next build - in between working on our current home. I got the footing in over a year ago so one benefit is the settling should be done when I get to the oven. Hope all are well!

[SableSprings]

Welcome back! Hope your 4th of July is a great...at least dealing with a heat wave in New York is probably a bit easier than hurricanes in Belize. So are you going to do a cast oven again or start stacking firebricks?

Yes, always good to have that foundation settling question/worry out of your worry list. Looking forward to your upcoming build.

[UtahBeehiver]

Plus one from Sable Springs, looking forward to seeing what you do now in NY. I was always impressed by your dry stack stone base on a previous oven.

[david s]

Hi Matt, nice to hear from you again. If you are using the clay you harvested, for a cast oven, you may need to process it a bit. Are you intending to build a cob oven? If so you will need a lot more than the 30-40 lbs you have already..
If you intend on using the clay to make a homebrew casting, I suggest you use a 3:1:1:0.5 recipe, ie sand, OPC,hydrated lime, powdered clay. Clay imparts considerable shrinkage as you know from the extended discussions we’ve had about it, This shrinkage varies from one clay to another so you could test it by working some into a plastic state, measure its length, allow it to dry then re-measure. It will be in the region of 5-10%. The shrinkage can contribute to severe cracking as the casting dries. If this is how you intend to cast you will also need to reduce the clay to powder so its addition is uniform. This requires drying the clay, pulverizing it and then sieving out organic material and larger stones with a course drive (say around 5mm) . The dry powdered matisl is then ready to use in the proportion of the recipe by volume. There are probably quite a few more well documented homebrew cast builds in the “Other Ovens” section, since your past activity here, that would be helpful to read.
All the best,
Dave

[stonecutter]

Hey guys. I’ll be building another brick oven with a stone surround. I’ve got something new planned for that though. Just to be clear, I’ve never built a cast oven. The clay I harvested was going to be used as a component for mortar. I found some pretty nice brick for the oven itself - but again, that never had a chance to get off the ground.

David - that clay was at my house in Roatan, Honduras. So no, I’ll not be using that.

[david s]

In that case save yourself some labour and time and just buy the bricklayers clay.
The recommended mortar addition is not to exceed 7% as strength then begins to be reduced and shrinkage increased.
That’s why I now suggest halving the clay proportion to 3:1:1:0.5 for both the homebrew castable and mortar.