[papercreters] Re: Using papercrete to insulate the chimney in a rocket mass heater

Hello--so far I've mostly been a "wishful lurker" to this site(wanting to use papercrete extensively, only being able to dabble a bit, reading whatever time allows). Having used a rocket stove last year in the house we are in the process of building, this post caught my attention, so I thought I might reply with what little bit of experience I have.

A couple of years ago we were lucky enough to find (at a yard sale) a 3' tall (approx) metal box with a 6" stove pipe attached inside (I think it was made to be used as a double-wall to insert through a wall). When we got to the stage we were ready to build our rocket stove, we simply filled the space between the pipe and the box (about 1-2" wide) with wood ashes. We figured it was the perfect insulator--non-flammable, non-heat-conductive (is that a word?) and cheap.

To make a long explanation short, we set it up on a couple of cinderblocks, the 55 gallon barrel fit down exactly over the top of it onto the same cinderblocks with a couple-of-inches space at the top, a 6" elbow pipe fit in at the back for the smoke to go out, the burn box between the cinderblocks and out the front was made out of bricks, then we built a wooden box around the cinderblocks and filled it with plain dirt to cover all the air cracks. We didn't have to cut any holes in anything metal--which was good because we didn't have any way to do that.

On the subject of papercrete, several years ago I was doing some experimenting with papercrete (did you know, by the way, that while papercrete "bricks" are setting you can place small rocks/other articles in the top in different patterns and they turn out beautiful? Don't try putting the rocks in patterns in the bottom of the molds, however, because they fall out later). Anyway, I had made a few blocks and, as it was somewhat cold outside at the time, I had set them up next to our woodstove to dry faster. That evening I noticed one had fallen over quite close to the stove and had started to smoke a bit, so I took it outside and leaned it up against the aluminum siding on the porch, figuring it would just go out since there was only a little smoke and no actual fire. The next morning I went out to get it, and it was gone--for a moment I wondered who had taken my papercrete block, then I noticed a small pile of ashes on the porch, and a yellowed spot on the aluminum siding. Can anyone say "smoldering?"

After that experience, I myself wouldn't use papercrete anywhere near extreme heat unless some type of fireproofing (borax, maybe) had been added--maybe not even then just to be safe. We're actually in the process of getting our rocket stove ready to place cob/clay around it to turn it into a mass heater this year. We are, however, planning on using papercrete as mortar between stone/cordwood on the outside of our house and maybe on one of our interior walls for a pattern/texture when we get that far ;p

--- In papercreters@yahoogroups.com, "oystein_tandberg" <oystein_tandberg@...> wrote:
>
> Hi!
> I was wondering if anyone has any experience in using papercrete to insulate chimneys? I'm planning to make a rocket mass heater, and I see most people use perlite, but perlite is very expensive here, so I was thinking using papercrete instead – ideas anyone?
> Best regards
>




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