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azpizzanut 11-24-2010 06:18 PM

Perlite/Mineral Wool
Hi All,

I want to pass along some things I learned about perlite from a builders supply employee and about mineral wool from my own experience.

Perlite is manufactured in a city near Phoenix, Arizona (among other areas around the world). I learned I can't buy perlite from the local manufacturer directly but I can get it through companies that repackage it for the retail market, including Lowe's and Home Depot. Perlite is sold in three grades and possibly more depending on its intended end use. Commonly there is a commercial grade, horticultural grade and then block filler grade. Perlite also has many industrial uses but this missive isn't intended to go into those.

Some perlite is screened to produce block filler and has medium and fine particals. It is quite dusty. Perlite block filler may be coated with silicone to help it settle into block voids. It is an insulation.

Horticultural grade perlite is a little less dusty and has generally larger individual pieces. It is used to make or mix with potting soil and soil amendments. I have personal experience with block filler perlite and horticultural grade perlite since I've used both to make hearth insulation and dome insulation mixed with Portland cement.

There is a HUGE pricing variance from retailers for perlite products. Home Depot sells a 2 cu ft bag for $17 and a seemingly identical block filler product from a builders supply sells a 6 cu ft bag for $28. A supplier of horticultural perlite sells it for $8 for 3.5 cu ft.

I'll fill the enclosure around my 36" oven with horticultural grade perlite from a local supplier for roughly $32 vs $120 from Home Depot. It pays to shop around.

Mineral wool is available if you do some research. I found it at two locations in the Phoenix area. One from an insulation specialty business and another from a building supply business. The price difference for the same general amount was roughly 50%. The kind I bought is in batts about 4 inches thick. It is firmer than fiberglass home insulation and cuts easily with a hand saw to provide precision shaped/sized pieces for fitting between the studs and voids in my oven enclosure. Mineral wood provides as good as, or very slightly better "R" insulation value than perlite and vermiculite and withstands higher temperatures than home type fiberglass insulation. It depends on the density. Information about the "R" value of mineral wool is a little difficult to find but is available on the internet if you are persistent. It is as dusty as fiberglass insulation and just as "itchy". Wear gloves and a face mask.

Today is Wednesday November 24th. I will place loose perlite into the sides and roof area of my oven by Monday November 29th. Then hopefully put the roof covering in place. Curing fires will follow shortly thereafter. Then stucco the exterior, finishing touches .............and pizza by Christmas.


GianniFocaccia 11-25-2010 09:29 AM

Re: Perlite/Mineral Wool

Thanks for the analysis. Very informative. Can't wait to see your Yule pies. :)


C5dad 11-28-2010 09:40 AM

Re: Perlite/Mineral Wool

Where did you source your pearlite? I was planning on stopping by the plant in Superior and see if they would sell me some on the side, though was not sure if it would happen.



azpizzanut 11-28-2010 09:53 AM

Re: Perlite/Mineral Wool

SIMPLOT, 19th Avenue north of Loop 101.


oventhusiast 11-28-2010 10:32 AM

Re: Perlite/Mineral Wool
Has anyone looked into this stuff for dome insulation?
Rock Doesn

azpizzanut 11-28-2010 12:40 PM

Re: Perlite/Mineral Wool
Hi Rick,

I'm using mineral wool in combination with Perlcrete for insulating my oven. Mineral wool is also known as stone wool, rock wool, slag wool and other names. Roxul is one of several manufacturers of this type of insulation. Yes, others have recommended/mentioned mineral wool insulation on the FB forums. The batts I purchased have roughly the same insulating value as vermiculite, Perlite, and fiberglass wool. Technical information is generally hard to find on the internet but you can eventually locate it. In my case it was simply an option to ceramic fiber blanket and available locally. It came in a large bale of five batts, part of which I used to cover the dome, held in place by wire, and the remainder I stuffed into the corner voids of the enclosure. The remaining voids will be filled with horticultural Perlite. I hope this answers your question.

C5dad 11-28-2010 05:07 PM

Re: Perlite/Mineral Wool

Originally Posted by azpizzanut (Post 102895)

SIMPLOT, 19th Avenue north of Loop 101.


Thanks! I did not even think of Simplot!!!

Have a great evening

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