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I am trying to build a foundry. The Youtube video refers to 4:1 Perlite:Fire Cement. But the shop also offers Fire Concrete. I don't know what's the difference.

Could someone please explain the difference?

Link to the video: https://www.youtube.com/watch?v=tTPdybtO-a0

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migrated from homebrew.stackexchange.com Sep 19 '12 at 12:59

This question came from our site for dedicated home brewers and serious enthusiasts.

    
I've not used either in any of my brews. Is this a brewing question? –  mdma Sep 19 '12 at 11:29
    
It's a "casting metal" or "foundry building" question. I couldn't use the tags "foundry" "casting" because the site didn't let me. ... Oooh, wait .. "homebrewing" as in "beer brewing" and not in "homebrewing equipment" ... This is .. embarrassing :( –  Jan Krüger Sep 19 '12 at 11:55
    
Can you insert a link to the video? If you don't have the rep, paste the url as a comment, and one of us will do it for you. –  Chris Cudmore Sep 19 '12 at 13:11
    
-1 for no link to video leaving readers wondering, "huh?" –  The Evil Greebo Sep 19 '12 at 14:08

1 Answer 1

up vote 6 down vote accepted

TLDR; - Concrete is poured into a form, for structural members. Cement is spread as a glue.

Cement is a glue. Concrete is a mix of aggregates, held together with cement.

If you're building something structural (to support a load -- such as itself), you'd buy the concrete. If you're using it as a skim/finish coat, or to attach firebrick, buy the cement, and (possibly) mix it with some very fine aggregates - depending on the use.

See this answer for more detail on cement/concrete in general. What actually happens if I vary proportions of cement and sand in mortar?

EDIT: After seeing the video, I now understand. What you are making is a light, weak concrete using the cement and perlite as an aggregate. You need to buy the fire cement, not the concrete. (You could use concrete and omit the perlite, but I think it would be pretty heavy.)

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Thank you! What will be more temperature resistant as I don't want to melt aluminium but brass and bronze which has a higher melting point than aluminium. –  Jan Krüger Sep 19 '12 at 18:06
    
I think the perlite mix will be better insulated. It might keep the outside a bit cooler. –  Chris Cudmore Sep 19 '12 at 18:07
    
Thank you for the help! :-) –  Jan Krüger Sep 20 '12 at 5:12

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