Phil Stevens

Hi Dan -

Barrels have been used on RMHs for many years now and reports that come back from early builds aren't typically talking about barrel burnout. I think the main things that are at play here are the reducing environment inside the barrel, which keeps the steel from being eaten, and the way the top radiates heat away as quickly as it's imparted by the gases from the heat riser. There is an upper limit to how hot the barrel top and sides will get in operation, and although it varies from build to build, no one has had problems with molten steel. We're talking about 300 C or so, far short of 1500 C (although by the time carbon steel reaches 1200 it is subject to deterioration well before it flows).

In the burn tunnel and heat riser, we are trying to keep the heat in as much as possible, so we insulate and hence the temps those materials withstand will quite easily exceed 1200 C. This is the main difference: we're retaining heat in the burn zone to support complete combustion, but once it reaches the barrel or bell, we've flipped the goal and now we're trying to shed heat from the gases as efficiently as possible. Thin steel does this well, and it's cheap and readily available in an extremely useful configuration, so there you go.

When I'm doing a lime plaster as an exterior finish, I add around 2-5% by volume to the mix of lime putty and sand and I may have tested up to 10 when I first experimented with pozzolans. I don't think you'd have any problems adding more, although you'd most likely want to test different proportions as Glenn advised. The ash will make it harden much faster than an unmodified lime plaster. So will contact with the concrete subfloor...as soon as you trowel it on, that will start sucking the moisture out of the mix.

Lime putty is just hydrated lime that has been mixed with water and allowed to sit. The longer the better...if you've got a barrel that's been sitting around that's fantastic.

Don't lose hope...my mother-in-law will be visiting next month and we can see if she would take it back to Oregon in her checked bags, then ship it on from there. First I have to see if Blackwoods will take my lowball offer ;-)

There were two, and if my memory serves they were 15 cm diameter. I could ask if they'd let them go for $100 for the pair. Could even ship one to you, but getting it across the Pacific won't be cheap.

I've got a rocket oven in the planning stage and would really like to install one at the end of the burn tunnel where it transitions to the heat riser. Am I nuts for wanting to do this?

When I designed the current iteration of Chez Chook, I had just enough salvage siding to make a box that sat up off the ground. It's probably about 80 cm wide, 1 m high, and 2 m long. The bottom is a tray that slides out for easy cleaning. I load in about a 5-10 cm depth of clean planer shavings and sawdust and scoop it out when it starts to smell like ammonia.

On the ammonia issue: Last month I decided to try incorporating some biochar with the soiled litter (instead of changing it) when the smell appeared. I put on about two shovels' worth and in under two days the smell was gone. It's still not smelly and there are 30 birds in there every night. This is pretty amazing.

I haven't seen bees in my chestnuts when they're flowering, nor in the hazels or walnuts. The only nut trees at our place that get any attention from pollinators are the almond and the macadamias. The latter are full-on bee party trees when they are in flower.

What about borosilicate glass as used for wood-burning stoves? I've seen thick round industrial-grade castings that were made for observation ports in kilns...in fact, the last time I stopped in at the local Blackwoods they showed me a couple that they ordered in for someone years ago who never picked them up, and told me no reasonable offer would be refused. If funding comes through for a couple of pilot projects I've got in the works, I might just be able to justify nabbing one of them.

Wayne, is that Ash Creek in the photo? No wonder you've got such good soil. My cousins' family used to live next to the elementary school and I spent big chunks of my summers there when I was a teenager. The north edge of their property grew trees about twice as well as the front part along the highway, all because the soil got better as you got closer to the creekbed.

Hi Trish -

Ash is one of the most common pozzolanic modifiers for lime. Adding wood ash to lime mortar or plaster makes it harder and more waterproof (hydraulic) than the lime on its own would be. Other additives that do similar things include volcanic ash, fired clay or brick dust, and silica. The famed Roman cements that have withstood weathering and even marine environments for 2000 years are made of lime and volcanic ash. I've done a fair bit of bricklaying and plastering with wood ash modified lime mortars and plasters, and I like the way they stiffen quickly, take a steel trowel finish for a tough "skin," and are able to handle exposure while they're still curing.

So, mixing lime putty with wood ash will definitely give you a trowelable mixture that will harden up nicely. I don't know how much insulation value it would have, but if you incorporate sawdust or straw,to give it tiny voids or air pockets, it could do what you want. Try some test mixes with varying proportions and see how they work...I'm curious too!

Welcome to permies, Jonathan! I concur with Henry. "Red Robin" is a common popular name. We've got several here and those leaves and flower clusters look very familiar. Dense, hard wood and the leaves are a good livestock fodder.