#1  
Old 07-22-2009, 02:48 PM
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Location: Austin, Texas
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Default Perlite Question

Fellow builders:
I've gotten to the point of getting ready to mix and pour the insulating layer of Perlite and Portland cement. I opened the bag of perlite for the first time and found that is sand like in consistency. Is that too fine to mix with Portland and pour? Should I junk the stuff and buy something else. Vermiculite in quantity seems to be tough to find here in Austin

Thanks
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Old 07-22-2009, 08:12 PM
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Default Re: Perlite Question

I think that that is too fine. Look for a coarser grain - something like 1/8 inch or better particles.
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Old 07-22-2009, 09:50 PM
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Default Re: Perlite Question

Sounds a bit too fine to me, as well. I used Vermiculite for the insulation slab - was labeled "medium grade" and until I reached the bottom 25% of each bag it was fine. The bottom of each bag was like brown talcum powder (a lot of settling), needless to say, I wasn't thrilled with the waste.

I switched to perlite for the dome (over 2" of blanket). The perlite was purchased from an online shipping products supplier, they sold about a half dozen different grades/sizes. Again, I chose medium. The perlite was much more consistant throughout the bags, it was about the size of Grape Nuts Cereal. As others have mentioned, it is much easier to judge whether you have mixed the portland thoroughly because of the white color.

The bottom line - I think you need it a bit courser, makes the mix more "airy" and adds to the insulation value (my opinion).

RT
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Old 07-22-2009, 09:58 PM
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Default Re: Perlite Question

Quote:
Originally Posted by RTflorida View Post
...

I switched to perlite for the dome (over 2" of blanket). The perlite was purchased from an online shipping products supplier, they sold about a half dozen different grades/sizes. Again, I chose medium. The perlite was much more consistant throughout the bags, it was about the size of Grape Nuts Cereal. As others have mentioned, it is much easier to judge whether you have mixed the portland thoroughly because of the white color.
....
RT
RT, can you tell us the website where you bought your perlite?

Thanks!
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Old 07-25-2009, 01:56 AM
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Default Re: Perlite Question

Re Perlite question:
Thanks, Neil, Florida. I am worried about this question of vermiculite grade/size. Is there an official view? It isn't mentioned in the instructions as you probably know (and sorry, I am not familiar with Grape Nuts cereal coming from Australia). Size of rice grains? A pea? Big as the end of your thumb? I bought one bag (vermiculite grade 1) and it's just a bit bigger than coarse sand, so I guess that's no good. Help!
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Old 07-25-2009, 06:02 AM
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Default Re: Perlite Question

Neither grape nor nut.
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Perlite Question-14_grapenuts.jpg  
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Old 07-25-2009, 10:15 AM
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Default Re: Perlite Question

I found my perlite at a hydroponics store, they had all grades from fine to coarse and the price was very reasonable
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Old 07-25-2009, 11:15 AM
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Default Re: Perlite Question

Only kind I've found so far was Miracle-Gro and it's not cheap.. if someone has an online source please post it!
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Old 07-25-2009, 11:22 AM
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Default Re: Perlite Question

I found perlite in bulk at a local hydroponics store, and at a good price
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Old 07-25-2009, 01:10 PM
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Default Re: Perlite Question

here's where I bought mine: the shipping is more than the product.

Krum Horticultural Perlite Garden Plant Soil Aerator A - eBay (item 250465932618 end time Aug-15-09 05:36:32 PDT)
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