Question about thermal conductivity

[Forrest Roche]

I will be starting an oven soon and want to know if someone can help translate this information sent to me by a manufacturer here in Spain. I want a thermal conductivity of ~0.6 W/Mk for the floor and this what the manufacturer sent me:

0,60 λ10, SECO W/Mk (P=90%)

(Seco means dry but I'm unsure what λ10 means, or the P=90%)

Any help is appreciated. I want to build a low dome for Napolitan pizza but want to avoid paying for a biscotti floor from Italy if possible.

Thanks in advance!

[RandyJ]

Just remember you get what you paid for. Sometimes there is no replacement for the real thing. The full cost of a oven won't differ to much to include the floor you want. Once the oven is built you can't go back and change the floor easily.


If I include the pavilion over my oven it probably cost me about $10k to build everything on this oven. My last one 9 years ago was close to $7k so just keep that in mind.


Randy

[rsandler]

I can't make sense of the lambda 10 either; from searching around, lambda is used as a synonym for w/Mk or K value, so attaching that to a number separate from the 0.6 doesn't compute.

That said, are you sure you're looking for the right thing? 0.6 W/Mk is only a little more than most insulating firebrick I could find. You want dense refractory for an oven floor, usually a medium-duty dense firebrick. See e.g. this datasheet for medium-duty firebricks with conductivity above 1 W/Mk: https://www.sandkuhl.com/index_htm_f..._UNBRANDED.pdf

[Forrest Roche]

Just remember you get what you paid for. Sometimes there is no replacement for the real thing. The full cost of a oven won't differ to much to include the floor you want. Once the oven is built you can't go back and change the floor easily.

Thanks Randy

My floor will be laid over dry sand and clay over 15cm vermicrete and built inside the soldiers so that if I want to remove it it won't be impossible.

That said, and though I would prefer not to have to swap floors in the future, the company is one of the largest manufacturers of refractories in Spain and I trust their quality, I just want to make sure that I understand the specification. If I don't resolve all doubt, I will buy Bicotto di Sorrento. The shipping isn't outrageous to Spain.

In any event I'm on a much smaller budget; the oven will be small (80cm), will be built in a pre-existing enclosure, and all my materials won't surpass 1,000€ even if I buy the Sorrento. Which I suspect in the end I probably will.

Forrest

[Forrest Roche]

I can't make sense of the lambda 10 either; from searching around, lambda is used as a synonym for w/Mk or K value, so attaching that to a number separate from the 0.6 doesn't compute.

That said, are you sure you're looking for the right thing? 0.6 W/Mk is only a little more than most insulating firebrick I could find. You want dense refractory for an oven floor, usually a medium-duty dense firebrick. See e.g. this datasheet for medium-duty firebricks with conductivity above 1 W/Mk: https://www.sandkuhl.com/index_htm_f..._UNBRANDED.pdf

The oven will be a low dome/Napolitan so according to all my research the firebrick generally available to me here in Spain has too high thermal conductivity, the Bicotto used in the Napolitan ovens has around 0.6 or less, according to my reading on pizzamaking forum where there is more information about the construction of these ovens in Napoles.

I'll probably give them a call tomorrow because I also had formed the impression that the lambda was synonymous so I'm thinking maybe they're saying that the range of the conductivity could be from 0.6 up to 10 which I'm not sure that makes sense either, what do you think? Can refractory conductivity go that high? Or is that more like conductivity of copper?

In any event I'll just call them tomorrow and ask to speak to somebody who can actually answer the question because until now I've just got hold of a receptionist who sent me the spec sheets.

[Forrest Roche]

Okay copper w/mk is 385 so maybe it is 0.6 to 10.

[Forrest Roche]

TXCraig replied to me on Pizzamaking forum, the lambda is definitely10, so Biscotto di Sorrento it is

[david s]

Thermal conductivity is only one characteristic of the most suitable material for an oven floor. If seeking a high thermal conductivity as the only desirable quality, you'd choose steel which we know is a poor solution because the high conductivity leads to burning the bases and a rapid drop in temperature. Other considerations are thermal mass, resistance to thermal shock and spalling resistance.
There are so many different units used to measure thermal conductivity and its reciprocal, insulation value, that their conversion and comparison becomes extremely difficult if not impossible. Best solution is to stick to the materials that have proved themselves in practice, but balancing availability, performance, longevity and cost. From users reports, high duty dense firebrick is a bit too conductive, a better performer is medium duty dense firebrick. The Italian biscotti has been developed over centuries of continued use, so probably has the most extensive testing of performance and suitability.

[Forrest Roche]

Best solution is to stick to the materials that have proved themselves in practice, but balancing availability, performance, longevity and cost.

Thanks David.

I'm always willing to experiment if mistakes can be corrected, but in this case the conductivity is a disqualifier so I'll place an order to Italy.

Forrest