I guess there's no sure way of eliminating ash altogeather, I do wait for it to cool down but if it's night time and it's still got some hot coals I bite the bullet and empty it out regardless.
The worst wood I have ever burnt for ash was Jacaranda, seriously I'd say half of it was non combustible. I was emptying the ash out every 2nd day.
Iron bark I'd say you can burn a ton to get a bucket of ash. I'm assuming it's all to do with the carbon content of the wood.
Hey Jeff,
You're right, you have to deal with it one way or another but as you note, the type of wood you burn makes a massive difference.
Ash is the stuff in wood that doesn't burn (obviously) and is the mineral elements in the wood - sodium, potassium etc - that the tree was using as part of its metabolism. So when
@woodchip rookie is honking his ash, he's getting his daily salt requirements among other things. Sapwood which is where much of the movement of stuff in the tree is occurring has higher mineral content and therefore ash, compared to heartwood which is structural and the channels for movement of stuff are blocked. Bark is higher again in ash content.
E. rubida (Candlebark) is a touch less dense than peppermint but has a stark difference in ash content between heartwood and sapwood. Peppermint sapwood is not much worse than heartwood in ash content, even the bark is not too bad. I'll burn the candlebark heartwood (which is orange) and has very little ash but small branches with bark on them - forget about it, the ash content once partially burnt smothers the remaining combustible bits which then can't burn properly so you end up with a firebox full of ash and unburnt charcoal in a few days. You can mix in a little of that with a low ash wood like peppermint or red gum and it'll burn down better eventually but I'd rather not have to burn any of that at all. I take that down to my brother in Melbourne, it's all the same to him. So the lower the ash content, the cleaner and more complete your combustion is going to be.
This pic was candlebark from last winter in the fire and you can see the clear delineation of heartwood and sapwood by the ash production.
The carbon content is the mass for a given volume (density) and the more of that you have for a lower mineral content the better. That's why the ironbark you get up there is so popular - very very dense without the high mineral/ash content. If I had ironbark, I wouldn't bother with peppermint or candlebark - you get an extra 300kgs per cubic metre or 1100kgs extra per cord over peppermint and 2480kgs extra per cord over black spruce!
@dancan would go into conniptions.
