Wednesday, December 23, 2015

Rocket Mass Heater - A Beautiful Mud Pie

I think our rocket mass heater project is nearing completion.  Thank goodness!  This project has been lots of fun, but we're ready to take a break from playing in the mud.  

I took the picture above from my pillow on a recent cold winter morning.  There was frost on the grass and mist in the air, but the early morning sun beams were lovely to wake up to.  I can't wait until I can start a fire on chilly weekend morning like this one.  

I spent a few hours one weekday evening rebuilding the clay ring that connects the barrel to the exhaust.  This is the part that we let crack by stoking the fire too hot during our first in-side fire.  This time, I made the first layer much thicker (about three inches), and made the cob quite sandy.  I still think this is the most likely spot for failure.  We've tried to prepare ourselves for someday having to chip the barrel out of the cob and re-design this junction.  Maybe a shorter heat riser and a longer barrel would be better.  We'll see. 

Brandon and I have perfected our cob making technique.  We pour a bag of sand on the tarp, then put three of four shovel fulls of soppy wet clay, and then Brandon pulls up the edge of the tarp to roll it all together.  

I, wearing my muck boots, stomp the sand and clay pile flat, then Brandon lifts the tarp and rolls it together again.  While I'm stomping, he moves to the other side of the tarp and we do the roll and stomp thing about six times before we add a little straw and mix and stomp some more.  By the time the batch is done, Brandon's arms are tired, my thighs are burning and my heart is pounding, so I need a moment to catch my breath while Brandon puts the finished product in buckets.  Making cob is a good workout.   

The chickens make sure the straw is mixed up good, and that there are no extra seeds in the mix.  Good chickens.  

On top of the first three inches of sand and clay cob, I added another four inches or more of sand, clay, and straw cob around the base of the barrel.  

More cob went in in and on the bench, along with as much rocks and rubble as we could fit in.  

I used a bunch of salvaged bricks along the floor, with more cob between them.  I think the bricks give it a tidy edge, and hopefully will make it easier to mop the floor without getting the cob wet.  With all the bits of straw sticking out, the stove looked more like a woolly mammoth than a dragon.  

Brandon and I were talking with someone who dreams about having a wood stove someday.  We briefly described our project.  "You're using a metal barrel, and mud?" he asked.  And then dismissively "If it's not beautiful, my wife wouldn't have it".  I think the implication was that our stove wouldn't be beautiful!  What's not beautiful about fire, earth, and steel?  

To give it a less woolly appearance, and to make the surface nice and smooth, we're adding a layer of wet sand and clay cob to the whole thing, and smoothing it out.  Like putting icing on a giant mud pie.  

My mom gave me a box of assorted marbles.  Marbles seem appropriate for a stove made of fire brick and clay, since they are made of glass melted in a kiln, right?  It's fun to find places between the bricks to stick them.  

Once Brandon finished smoothing the finish layer of plaster around the fire box, he added a fossil and some glass pebbles.  I thought it looked even nicer after the cat took her turn decorating with her paws.  

Once I finished adding a row of bricks along the base, Brandon used a piece of a plastic cutting board to smooth the finish layer around the base of the barrel.  We haven't decided yet how to treat the surface once it's all dry.  Some people use linseed oil, and others have used an olive oil based soap. Maybe stucco?  

1 comment:

Anonymous said...

It is looking so pretty!


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