Neapolitan sand-salt mix under the oven floor? Pompeii Oven Construction Discuss Neapolitan sand-salt mix under the oven floor? in the Pizza Oven Design and Installation forums; I've worked out most of the details on my next oven build, which is going to be a Neapolitan type ...

[pacoast]

I've worked out most of the details on my next oven build, which is going to be a Neapolitan type oven, built as authentically as possible. This is not for a commercial venture, so it's out of my budget to hire some masons from Napoli to come build it for me & remains a DIY project.

I'm interested in the traditional "insulation" or bedding that Napoli builders use under the terra cotta cooking floor. Which is a sand-salt mixture, perhaps with ash or crushed volcanic glass as well. Yes, I know that modern insulation like CaSi boards are superior insulators. And a better way to go for most ovens.

But in the interests of doing this build the traditional, old fashioned way, does anyone here know more about the composition of this bedding or how it is traditionally mixed? Presumably the sand is not intended to be an ideal insulator, but rather to slowly absorb some heat. It might increase the oven warm up times, but still absorbs heat slowly enough to not really cool a fully heated floor. But enough that it can help moderate temperature swings in the floor and possibly even help recharge the floor temperature from the bottom when you are making a lot of pizzas. I've also heard that something similar was traditionally used in Spain (& probably a lot of other places) as well.

Any thoughts on how this might be optimized? Or has anyone here seen the floor of an authentic Neapolitan oven being laid?

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[david s]

Anything that will create lots of air spaces would work. I think that is the theory behind the broken glass idea and probably the same for the salt if you used rock salt. Sand would also create spaces between the grains. The denser the material the poorer the insulation. Sand salt and glass are all way heavier than vermiculite or perlite. I think folk just used whatever was available and cheap. We now have access to all kinds of materials that the ancients never had. It would be a pity if you found that your oven lost heat out of the floor easily because it will be impossible, or extremely difficult to replace your floor insulation once your oven has been built. Stick with vermiculite or perlite