making pompeii oven (with crack problem) waterproof

[fluxia]

hello,

I have a question about how to make the oven waterproof.
I built my Pompeii oven a couple of years ago but I have not used it a lot for various reasons.
Recently I decided to fix it ( I had to add insulation under the oven floor as it was loosing heat) and I have now have to decide how to make it waterproof.
My oven is insulated with vermicrete (I would say probably about 10 cm thick). When I cured it I got a big crack on the top. I supposed I used too much water in the vermicrete but I also made a fire a bit too big at the last stages of curing.
I then used the oven a few times and I was able to cook really good pizzas, but a lot of steam still was coming out of the crack.

Yesterday I re-used the oven again; a lot of steam still comes out of the crack when the oven is hot.
Now, I understand that the crack is not a big deal in itself, the oven seems to be structurally ok and all that water inside has to come out somehow, therefore is good that it can come out from the crack. However, until I have steam coming out of it I cannot seal the oven properly. I would like to paint it with some waterproof heat resistant paint. So at the moment I am protecting the oven with a tarpaulin.

Can anyone advise what is the best way forward please; should I use the oven until no more steam comes out and then close the crack and paint it (and anyone has an idea of how long this may take?) or is there anything else I can do?

Thanks in advance

[david s]

Re: making pompeii oven (with crack problem) waterproof

Just keep firing it and the water will eventually come out. Part of the trouble with doing this is that water will recondense on the inside of the outer shell. You could help it by drilling some holes in the outer shell so the water will have additional pathways out of the insulation layer. You can plug them whe you're satisfied it's dry.Making a permanent vent is also a good idea.

[fluxia]

Re: making pompeii oven (with crack problem) waterproof

Thank you David. Your advice is really helpful. I did not think about a permanent vent and I agree it's a good idea. Could it be a good way to possibly prevent further cracks in future? I presume I'd better do it on top of the dome where the main crack is.