vermiculite or perlite?

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Railrider1920

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Dec 14, 2010
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If you are going to heat a piece of metal up and need to keep it hot to let it cool very slowly, do you put it into perlite or vermiculite? From a search I'm thinking that it's vermiculite, but probably either one could be used.

The only perlite I have found has miracle grow in it. Think it could still be used if I can't find some with out it? Is vermiculite sold in the gardening business as well? Or are they pretty much interchangeable?
Thanks

Vermiculite
From http://www.epa.gov/asbestos/pubs/verm.html
Vermiculite is a naturally occurring mineral composed of shiny flakes, resembling mica. When heated to a high temperature, flakes of vermiculite expand as much as 8-30 times their original size. The expanded vermiculite is a light-weight, fire-resistant, and odorless material and has been used in numerous products, including insulation for attics and walls.

Pearlite
From http://www.thefreedictionary.com/perlite
A natural volcanic glass similar to obsidian but having distinctive concentric cracks and a relatively high water content. In a fluffy heat-expanded form perlite is used as a lightweight aggregate, in fire-resistant insulation, and in soil for potted plants.
 
You should be able to buy vermiculite from Lowes or Home Depot or a garden supply store. Call first in case they don't or are out. I bought my last bag from a garden supply but I also bough a small bag from Lowes.
 
You may have to wait until spring for the stores to carry it again.

I think both work.?


There is some mention of Vermiculite now contributing to silicosis...
 
The last time I bought any, perlite was all that was available locally. Wal-Mart garden center carries it in big bags for cheap. Worked fine for me.
 
Thanks guys. Have to go to lowes tomorrow so I'll look around there. If not, we have a few feed and seed / gardening stores around. Maybe one of them will have either one.

I have seen it in wally world, but it has miracle grow in it too.

That silicosis sounds like some nasty stuff.
 
Look for Schultz perlite at walmart. I haven't checked recently and availability may vary by location, but that's what they used to carry. Can look for the same stuff at Lowe's etc, or a nursery in your area.
 
I bought both perlite and vermiculite at the hardware store (canadian tire) in the garden center for under $5 a bag. I have the vermiculite in a bucket for slow cooling and mixed the perlite with some stove cement for a castable refractory. Silicosis is bad but just don't stand over the bag while you are shaking it out. Or wear a filter mask.
 
A good alternative to a box of vermiculite is a roll of Kaowool. Just lay the hot blade on the wool and roll it up tight. Snap a few bungee straps around it and set it on the bench and go to bed. The blade will often still be hot to the touch tomorrow morning.
 
I've always found lime to be a much better insulator.
I now use my heat treat oven, but I used to keep an outfit like shown here. I would heat up two large pieces of steel and bury them in the lime a few inches apart to heat up the lime and add extra heat.
The longer you can keep the new blade hot the better the action you get.
Then heat up the new blade and place between them and cover with a few inches of lime.
I once went out to my barn where I used to forge about an hour after I placed a blade in and when I uncovered it, it was still glowing red in the dark!
anneal1.jpg


anneal.jpg
 
Railrider1920 said:
The only perlite I have found has miracle grow in it. Think it could still be used if I can't find some with out it?
Click to expand...

I used it once. I placed a 1 1/2" X 10" piece of heated 1080 in it in the evening. When I came back the next morning it had grown into an eight foot grader blade. So I guess I don't recommend it. ;-)

- LonePine
Alias Paul Meske, Wisconsin
 
Ha ha. I thought I might get a response like that one.

OK, what is a "grader" blade? Not a knife maker yet and certainly not a gardener. No idea what grader refers to.
 
The koawool idea sounds good, but I haven't gotten any yet. Two of the places I found to get it online aren't taking orders right now. One for inventory and another because of health reasons. I did find a place about 1.5 to 2hrs away where I can get a box of it for about $75-80. If I was to get it, could I sell the rest here in the classifieds with only having 60 some odd posts?

I did get a bag of lime today. I'll probably make a box for it and give it a try.
 
Hmmm.. lots of food for thought. I thought about making a wooden box to anneal in but but was a little worried about it being flammable.
I've had a hard time finding vermiculite in large quanity. Those small boxes get expensive quick. large bags of lime will be easier, just don't joke about hiding bodies.

Stacy, I really like the kaowool idea, one of those "why didn't I think of that" moments. When I buy for my forge and such, I'll have to get a little bit extra. For now...I'm going to need a little lime for the garden anyways.
 
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