Dome shaped oven

[Joe S]

New to the forum and like many others found this forum late after watching many YouTube videos. I started to accumulate most of the materials from watching those vids and even did demo to my yard in preparation of the build only to now find this forum. I’m sorry in advance if this has already been answered but I’ve been reading up for about a day and didn’t exactly find the answer to my question. I know many if not all on here have condemned the exercise ball method with vermiculite/cement but is that because of the materials or all together will not work. Will the ball work if used with the proper materials to construct a strong and insulated dome? Would vermiculite mixed with refractory cement be the correct approach with a layer of insulation on top followed by another coat? I understand the base constructed with 4 inch vermiculite/refractory cement with firebrick on top seems to be enough to hold heat. I appreciate any advice that would be helpful.

Joe

[UtahBeehiver]

As you know there are not many fans of the vcrete or pcrete over a gym ball for the primary dome, here on this site. There are a lot of YouTube vids out there and some are really not in the best interest of the builder but rather after "subscriber: hits some are just plain bad, they are one offs. On this site you have the collective knowledge of hundred of builders. There have been a number of successful cast ovens built by forum members using a homemade or commercial "dense" refractory over a sand mold. Then using a mi of p or v crete for under floor and over dome insulation. Don't fall for these quick and easy vids, the work is the same using a dense refractory over p or v crete for the dome. Either case you need a firebrick floor , insulated underneath. PS, P or vcrete alone in not a sufficient structural base for the oven, you need a min. 4" rebar and mesh concrete base then the insulated layer then the firebrick. Search the "other type oven section" there were some posted links by David S on documented cast ovens

[Joe S]

Thank you for your response. I understand now that these videos are useless. When you say dense refractory, is that refractory cement? Refractory mortar? I apologize if these are elementary questions, I have no prior knowledge of masonry work or pizza oven builds and appreciate all the info I can gather.

[david s]

Refractory cement = calcium aluminate cement which is the active ingredient of mortars and castables
Refractory mortar = refractory cement + fine aggregate (usually sand)
Dense Castable refractory = refractory cement +high temperature aggregates, clay, burnout fibres and other secret goodies
Insulating castable refractory = similar to dense castable refractory but also containing a high proportion of insulating aggregate (typically perlite)
Home-brew castable = 3:1:1:1 sand, hydrated lime, clay, portland cement

[Joe S]

Thank you David! Not sure if you can recommend a certain brand that has proven best to work if I decide not to use the home brew method.

[david s]

There are lots of refractory suppliers with a variety of different castable. Call or email them for advice relative to your application, but do ask for dense castable. Most are designed to withstand at least double the temperature an oven will see and they contain high temperature aggregates that are really a massive overkill. The price will shock you and the short working time can make placement difficult. The upside is that calcium aluminate castables do not require extended damp curing and the resulting casting should be of a higher quality than the homebrew castable. If I were building a one off casting for myself I’d be using the homebrew because of its price and ease of working, but it is important to hold in the moisture for at least a week.

[Joe S]

Giving the cost, I think homebrew is the only choice. I have been on this forum for a few days looking for information on the castable dome. I have read many threads but I haven’t read anything from someone’s build that gives a breakdown on the amount of material needed for homebrew to cast the dome, let’s say with a interior diameter of 30”. Some product I would need to be delivered and the way things are now, delivery times aren’t as fast as they once were. It would be greatly appreciated if you can point me to a post that had mentioned this. Reading posts all day on an iPhone can make you dizzy!

[david s]

Try this
#22

[Joe S]

Just what I was looking for! Thanks David.