Food Grade Refractories - Ovenzz Brand from Harbison Walker


Somewhere at the end of each new brick oven is an intensely passionate chef or cook who labors over every ingredient. These artisans never compromise when it comes to their food’s appearance, texture, and flavor. There’s only one oven they want to stand behind: one that performs to the highest degree.

HarbisonWalker International’s NSF / ANSI Food Grade OVENZZ™ refractory solutions are a leading choice for commercial and residential oven suppliers, designers, and builders because our refractory materials deliver exceptional durability and cooking performance.

When you have an even and thermal-efficient heating environment, foods cook better and taste better.


We provide solutions for all kinds of brick ovens and cooking applications. Our NSF / ANSI food grade refractory firebricks, and high-temperature cements and mortar have a fireclay base to assure exceptional high heat capacity. And because our brick requires no priming, there’s no need for the hearth or deck to be fired before you start baking.

From small stoves to large commercial pizza ovens, we have just the right products to help ensure safety, and cooking efficiency. Our NSF-certified food contact products include:

OVENZZ™ BRICK — ASTM C27 super-duty firebrick, available in numerous shapes and sizes. This product is high fired and requires no priming.

OVENZZ™ LW CAST — lightweight, insulating castable refractory with extraordinary strength and excellent insulating properties. Suitable for casting shapes, pouring in place, and filling large cracks and holes.

OVENZZ™ LW CAST — provides a more thermal-efficient solution than dense products. It’s made with GREENLITE® aggregate, a higher-strength insulating product.

OVENZZ™ CAST — fireclay-based, cement-bonded, dense castable refractory. Suitable for casting shapes, pouring in place, and filling large cracks and holes.

OVENZZ™ BLOCK — a pre-cast, dried form of our OVENZZ CAST product. OVENZ BLOCK is the only brand for NSF certified pre-cast solutions in baking oven applications.

OVENZZ™ MORTAR — high-alumina, air-setting refractory mortar that is ideal for troweling.



At HarbisonWalker International, food safety comes before all else. Our OVENZZ™ products have been certified by NSF International. And all OVENZZ™ products meet American National Standard / NSF International Standard 51 for use as a food equipment material and are approved for contact with food.

And of course we always have our eye on kitchen safety. Our ceramic fiber blankets and bulk fiber products help keep oven exteriors cool and improve baking environment safety.

Click here for more information about Ovenzz Food Grade Refractory Products.

I just packed in and troweled my base insulation layer and 24 hours later it’s still as soft as it was when I troweled it. It doesn’t seem to be curing at all! I used Harbison Walker insulating castable which is basically shredded wool insulation and cement. How long does this stuff take to cure? Does it cure or dry by evaporation? I had it covered overnight because we we expecting rain but if I’m trapping moisture when I shouldn’t be, I need to let it air/sun dry. Please help! Ready to lay brick but stuck here.

Hi Mike,

Well, that sounds unexpected. I don’t have an instruction sheet for that product, though I did try to get one from HWI’s site. What does the packaging say about cure times?

For comparison, it takes several days to cure the homemade mix of Vermiculite and Portland cement, and about 48 hours to cure the Perlite/Portland cement mixture.

Air is important, even if you are expecting rain; cement cures by a combination of chemical process (generating heat as the molecules bond and crystallize) and evaporation. I wouldn’t allow a tarp or cover to be in direct contact with the area you poured, but instead open two sides enough to allow an air flow under the cover.

Others who have used the product may have experience to share. I used the Perlite mix which set up hard within a few hours and was fully cured within 48 hours.

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I agree 100% -

You need some airflow… and if you added a bit too much water to the mix, it might take a day or two longer to dry.

Thanks guys. I’ll give it a day or two more. I actually tried to use just a tad less water than instructed to avoid a soupy mix. The bag only says how much water to add (11 gallons per 50 lbs), nothing else regarding curing. It’s now been almost 4 days and it has firmed up a bit, but still Play-Doh firmness. No cover as we haven’t had any rain lately. Nowhere near strong enough for firebricks and an 800 lb oven

Mystery solved guys. Harbison walker sold me the wrong material. Their insulating cement does NOT get rock hard, it always remains somewhat pliable and so is unsuitable for this application. The correct product is greenlite 45. That is specifically designed as a sub-hearth insulation material that gets concrete hard. Even the guy I spoke to at Harbison had to make a few calls to figure that out. Unfortunately, their sales guys are not necessarily knowledgeable of their entire product line.

Oh, no! I’m glad you called them but so sorry to hear what happened.

The “easy” thing is knowing you have to take that material out of your oven floor. Seeing your posts on other threads, I know that you’ve seen what happens with an insulated hearth that is still retaining moisture.

I’m sure I don’t have to tell you that HWI should “make good” on their error. You might want to reconsider, though, whether you need the commercial product. I’ll continue to stand behind the Perlite/Portland cement mix as easy, inexpensive, and effective. I know you want to start laying your hearth floor and get moving on your build, and to my mind that’s the fastest route once you get the insulating cement out of your slab.

Thanks for letting us know, Mike, and keep us posted. We’re in your corner.

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You’re absolutely right. I plan on picking up the perlite and cement today. Thanks for your consistent support Matt, makes this whole process much less stressful knowing there are people out there ready to help. You’re great!


Hope your build is continuing well, Mike.

Here’s a link from a couple of years ago that has a lot more back and forth about this whole topic.

Base insulation: Into the void!

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