Your Kiln Questions, Answered

Size & Capacity

  • FlameWise makes two models:

    Campfire Size — 3 feet wide × 2 feet tall. Great for individuals, small properties, and first-time kiln owners.

    Burn Pile Size — 4 feet wide × 30 inches tall. Ideal for larger properties, conservation districts, farms, and community burns.

    Both models ship flat in 3 boxes (containing two interior and two exterior panels each).

  • At a full fill, the Campfire size can produce around half a cubic yard and the Burn Pile size about one cubic yard - however, most people don't fill the kiln completely.

    In a typical session the Campfire size produces around a quarter to a third of a cubic yard, and the Burn Pile size produces around a half to two-thirds of a cubic yard.

  • Flame cap kilns process feedstock at roughly 5 to 10 times the volume of the kiln.

    So for a Burn Pile size kiln producing close to one cubic yard of biochar, budget somewhere between 5 and 10 cubic yards of feedstock, depending on how dense or "fluffy" the material is.

    For a Campfire size kiln producing close to ½ a cubic yard of biochar, budget between 3 and 5 cubic yards of feedstock.

  • Yes - our customers have done exactly that - whether it’s a slight extension by adding a couple extra panels, or connecting panels from two kilns to form a big ring.

    We've seen this extension approach used with tractor-loaded material as well. Hand-loading tends to produce less smoke (because you add material gradually and maintain the flame cap), but machines can be used to move material right up to the kiln to make loading easier.

Feedstock & what to burn

  • Safety note
    Use clean, unpainted, untreated wood — branches, prunings, forest slash, orchard waste, and similar dry woody material all work well. Eucalyptus and other agricultural woody waste are fine too.

    Do not use painted, stained, or pressure-treated wood, as burning those releases toxic compounds.

  • These materials create insulating air pockets and do not process well in flame cap kilns. Sawdust is better handled with a briquette maker or added to compost. Leaves and dry needles have the same limitation — the kiln is best suited for solid woody material.

Durability & lifespan

  • We have not found an upper limit. The founder has done many dozens of burns in her own kilns without issue.

    Comparable flame cap kiln designs (like Kelpie Wilson's Ring of Fire) have been used for 100+ burns and keep working. Treat them well and they should last for years!

  • Yes, mild surface rust will develop over time — but this does not affect performance.

    We recommend storing the kiln vertically, so that any water can drain away. The kiln can be left outside under a tarp through winter without issue. It's a great option for community or communal-use programs that need a simple storage plan.

Water use & safety

  • When you’re starting out, budget about 100 gallons per cubic yard of biochar produced.

    With practice and technique, many people get this down to 50 gallons per cubic yard or less.

    For a typical Burn Pile size session (½ to ⅔ cubic yard of char), plan on 50–70 gallons as a practical starting estimate.

  • Personal protective equipment: leather work gloves, leather boots, long sleeves and pants in cotton or wool (no synthetics — they can melt), hat with brim, eye protection, hair tied back. Wear a breathing mask (N95) during quenching to avoid inhaling micronized carbon.

    Useful tools:
    • Thermal camera (large screen) — to find hot spots in char
    • Infrared temperature gun — to check kiln temperature
    • McLeod hoe — for raking out
    • Silicone-coated fiberglass welder's blanket — to cover the kiln and reduce water needed at quench

    Always have adequate water supply before igniting. Supervise the site for 30–60 minutes after the burn is complete.

Weight, storage & portability

  • Both kiln sizes consist of 12 panels (6 interior, 6 exterior) are flat and stack compactly — they fit in the back of a standard car. This makes the kiln easy to transport and store in a shed, garage, or under a tarp outdoors.

    The Burn Pile size kiln has a weight of about 95 lbs, and the Campfire size is about 50 lbs.

Ordering & lead times

  • To place an order, use the contact form. Let us know the size(s) and quantity you want and your full shipping address, and we'll send an invoice you can pay online through Clover, our payment system.

    We fabricate each kiln to order (we don't keep stock on hand). Fabrication takes approximately 3 weeks, and shipping adds about 1 week, so plan for roughly one month of total lead time from payment to delivery.

  • Yes. If you're in or passing through the Seattle area, pickup is available and sidesteps shipping costs entirely. We also occasionally coordinate handoff meetups along routes we're already traveling — just ask and we'll see what we can work out.

  • Yes — FlameWise ships to customers across the US. We've shipped to Colorado, Idaho, North Dakota, Texas, California, Minnesota, and beyond. Contact us with your zip code and we can give you a shipping estimate.

  • Yes. We work with conservation districts, universities, nonprofits, and grant-funded programs regularly. We can provide itemized pricing documentation for grant applications. Some grant programs require that orders not be placed until the grant is contracted — we can hold a quote and initiate fabrication once payment is received. Reach out and we'll work with your process.

Burn time & operation

  • Burn time varies based on feedstock type, moisture, and kiln size - budget at least 3 hours and up to 6.

    The smaller Campfire kiln will generally complete a burn faster than the Burn Pile size under the same conditions. You must remain on-site and attentive during the entire burn, and should plan to supervise for 30–60 minutes after quenching to ensure full extinguishment before leaving the site.

    We recommend patrolling to the site a few hours later to be extra safe.

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