BOOH IV

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Re: BOOH IV

Postby Nutcase » Sun Mar 03, 2013 10:07 pm

I've been doing some preliminary testing on materials and methods for lining a fiber blanket system, primarily using the furnace cement I got from Lowe's along with the Roxul. This is Hercules regular body high-heat furnace cement, nominally rated for 3000˚F. Here is a picture showing some results.

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The tube fragment on the right was made with about a half-half mix of the furnace cement with some gray modeling clay from my stockpile of random junk I've accumulated over the years smeared on a cardboard tube, rolled in some perlite, left to dry for a few hours and then tossed into the fireplace The resulting tube had the thickness and the fragility of a thick egg shell or a tortilla chip. There is also a pita bread effect, with raised bubbles. Messing around with it in the fire, it soon acquired a lengthwise crack, maybe due to the ends expanding and contracting differently when it was used as a chimney. It's been kicking around for weeks now and I haven't totally destroyed it.

The piece on the left I made more recently, just smearing some of the cement like peanut butter on a piece of the ceramic fiber blanket. I let this piece dry longer, but it was still somewhat pliable, like stiff leather, when I put it in the microwave. The pita bread effect was dramatic.

As this stuff dries, surfaces exposed to air develop a tough skin that slows further drying and traps water vapor, leading to big bubbles if brought above boiling.
Last edited by Nutcase on Mon Mar 04, 2013 1:05 am, edited 1 time in total.
Mark
(aka Nutcase)
Nutcase
 
Posts: 145
Joined: Fri Dec 21, 2012 10:35 pm
Location: NW Oregon

Re: BOOH IV

Postby Nutcase » Sun Mar 03, 2013 11:24 pm

So two days ago, we made this piece.

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My wife spread a layer of the cement 5"x23"x1/8" on a strip of paper, I spritzed a slightly larger piece of blanket with water and pressed it onto the cement, and then draped it along the length of an 8" diameter cardboard tube overnight. Yesterday afternoon, I baked it for several hours, starting at 170˚and working up to 230˚. Today we stuck it into the bottom of the otherwise unmodified BOOH IV burn channel and ran the system up to 900˚. This is what came out:

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On a macro level, the paper burnt off of course. The piece has sagged and the fuel inlet end has broken off, all correlating with the very uneven support and the loading from the fuel and the improvised grate. As with the earlier test piece, the bond to the blanket is good.

On closer inspection, one can see that the surface has a glazed appearance. Some of it has a greenish cast that looks like it could be the result of some sort of copper contamination, possibly a residue from the earlier run with the blue glazed pottery shard. The cement surface has an irregular, bubbled appearance. Looking at the edge of the crack, it looks like the inside still wasn't completely dry, so it has irregularly bubbled and separated, albeit on a smaller scale than before.

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The cement has actually fused onto the grate at a couple spots.

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The blanket material feels somewhat fused on the surface throughout most of the burn chamber. It's a thin crust, like a crisp cobweb, tapering off within the first foot of the heat riser.
Mark
(aka Nutcase)
Nutcase
 
Posts: 145
Joined: Fri Dec 21, 2012 10:35 pm
Location: NW Oregon

Re: BOOH IV

Postby Nutcase » Sun Mar 03, 2013 11:43 pm

I think perhaps my next step should be to put some of the cones used by ceramicists into the high heat zone and get a better handle on what is actually going on here, in terms of peak temperatures. Because only a surface layer is getting glazed, I suspect that the wood ash has something in it that is fluxing silica. It's certainly something to figure out, as it will be very easy to match and exceed the current operating temp by just using more insulation and sealing gaps you could stick a finger through. Putting a chimney on it could kick it up a notch as well.
Mark
(aka Nutcase)
Nutcase
 
Posts: 145
Joined: Fri Dec 21, 2012 10:35 pm
Location: NW Oregon

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