How to make a sand dome surface hard/crusty? Tools, Tips and Techniques Discuss How to make a sand dome surface hard/crusty? in the Pizza Oven Design and Installation forums; Hi, I am building my concrete oven on a trailer and I need a solution to make the sand dome ...

[Seb's]

Hi,

I am building my concrete oven on a trailer and I need a solution to make the sand dome surface hard/ crusty enough so that I can pour the concrete on it.

Any ideas of product I could put on the dome to make it hard enough?
Thanks for your help.

Seb

[Jed]

Originally Posted by Seb's

Hi,

I am building my concrete oven on a trailer and I need a solution to make the sand dome surface hard/ crusty enough so that I can pour the concrete on it.

Hey Seb,

Just drape a bit of plastic over the sand. That will help the sand hold it's structure. Hold it in place with duct tape and rope if you want. All the stuff will come out of the middle when you pull the sand out, or burn out with your curing fires.

Are you using a refractory cement? Regular cement will break down, spall, and loose strength at regular wood fire temperatures.

JED

[dmun]

Founders use a method of making the sand form rigid. Here's one recipe:

Casting molds have to be strong enough to pull apart to take out the casting model, it may be overkill for this application.

[Johnny the oven man]

Damp sand holds up well, then cover it with plastic sheeting.

[JoeyVelderrain]

I just covered my sand dome with newspaper before I put the refractory castable on it. It worked fine.
I know there is a thread on here somewhere of a guy in Australia that used paint on his sand dome and it seemed to work great for him. If I had to do it over again I would use the paint method.

[Seb's]

Originally Posted by dmun

Founders use a method of making the sand form rigid. Here's one recipe:

Casting molds have to be strong enough to pull apart to take out the casting model, it may be overkill for this application.

Sounds interesting, thanks... and congrats for your project!

I also red something about polymeric sand. Do you know anything about it?


Seb

[Seb's]

Originally Posted by JoeyVelderrain

I just covered my sand dome with newspaper before I put the refractory castable on it. It worked fine.
I know there is a thread on here somewhere of a guy in Australia that used paint on his sand dome and it seemed to work great for him. If I had to do it over again I would use the paint method.

You mean you put some refractory concrete on it? (sorry, I am french and my dictionary doesn't know castable...

Paint??? Why not but it doesn't seem to be strong enough, but I am surely wrong. Need to find his thread.

Tks

Seb

[Seb's]

Originally Posted by Jed

Hey Seb,

Just drape a bit of plastic over the sand. That will help the sand hold it's structure. Hold it in place with duct tape and rope if you want. All the stuff will come out of the middle when you pull the sand out, or burn out with your curing fires.

Are you using a refractory cement? Regular cement will break down, spall, and loose strength at regular wood fire temperatures.

JED

Yes, Jed, I will use refractory concrete.

[mr g]

Hi Seb, I'm the guy from Australia that used paint. The sand I used was bricklayers sand which is usually more yellow or orange in colour. This particular sand was the stuff that they use under concrete slabs when making homes. This has a higher clay content and forms and compacts more easily but regular bricklayers sand should do the trick. If possible avoid the regular white washed sand.
The sand should be damp but not wet - definitely not dry.
After that you can apply three or four coats of any water based paint you have lying around. The first couple of coats will get soaked up quickly but later ones will start to sit on top of the sand and form quite a firm crust.
After that I laid normal house hold cling wrap over the mould so that the concrete didn't stick to any of the mould.
Please bear in mind that I went to this trouble because I made ten ovens from the one mould. I don't know that you need to go this far if you have the right sand in the beginning. I've attached some photos for your info. Search for a thread called Wild Willy - there is quite a bit of information which can help you.

Regards
Mr G

[Archena]

Originally Posted by Seb's

You mean you put some refractory concrete on it? (sorry, I am french and my dictionary doesn't know castable...

Paint??? Why not but it doesn't seem to be strong enough, but I am surely wrong. Need to find his thread.

Tks

Seb

Castable simply means 'can be cast' as in cast in a mold. In other words, something that can be cast via a mold. Most castable materials (wax, metal, plaster, ceramic, et al) can also be shaped without a mold. In this case, the sand forms the mold for the interior (don't know if he used any form of a mold for the exterior). Unless I completely misunderstood (wouldn't be the first time) he made the oven itself out of castable refractory concrete, just as you are intending to do.


Did I make that confusing enough?