How to

Safety First:  Personal Protective Equipment

1. Eyes:  Use dark safety glasses when aiming the focal spot onto the kiln.  It's very bright.  The sunglasses will protect your eyes and make it easier to see.  We use welding goggles, shade 5 safety glasses.
2. DO NOT TOUCH!  It gets VERY hot during charring.  Internal temperatures reach nearly 600° C (about 1100° F).  The outside of the lid can exceed 200° C (almost 400° F).  And the focal point on the bottom is rated at 700-1000° C (1300-1800° F).  After cooling check the exterior temperature with a infrared thermometer to ensure it's at a safe temperature before touching.
3. Avoid even transiently passing any part of your body, limb, or hands through the focal spot.  It'll burn instantly!  
4. You'll be in the sun so protect your skin from UV.  Hats, sunglasses and sunblock are recommended.

Qt1 kiln (1 quart kiln)

1. Load the kiln with the plant biomass to be charred (grass, leaves, twigs, coffee grounds).  Then cover with the lid ensuring there are no gaps for air to sneak in through.
2. Set the solar cooker into full sunlight.  Turn it away from the sun so you can safely set the kiln onto the stove ring.  Then turn it facing the sun.
3. Using your PPE adjust the azimuth and altitude to get the focal spot on the bottom of the kiln.  Position the focal spot on one side of the kiln so that it will move across the entire bottom as the Earth spins.
4. Check the focal spot's location on the kiln.  When it is about to move off of the kiln, readjust azimuth and altitude to place it on the opposite side.  Repositioning is required about every 10 minutes or so.
5. Typically within a half hour the kiln will begin emitting smoke.  It may take longer if you began with wet plant biomass.  
6. Continue charring until the smoke ceases, then continue for another hour to ensure completion.  This typically takes 3-4 hours total depending on the mass you started with.  It may take longer if you started with wet materials.
7. When finished let the sun gradually move off of the kiln so it'll cool slowly.  DO NOT turn it away from the sun or otherwise rapidly cool it.  If you do the kiln will warp and cast iron that warps, breaks!
8. Once cooled measure the charcoal's mass using a kitchen scales if you want to keep a record of how much carbon you've permanently trapped.  Divide this mass by 2 to see how much carbon you permanently removed from the air.  To calculate how much carbon dioxide you've permanently removed from the air, divide the charcoal's mass by 2, then multiply by 3.8.  
9. Send the charcoal to the landfill where it'll be buried and stable for millennia.  Let's turn those landfills into coal seams!