Lava rock looking ash…?

[The.Devo]

View attachment 286318

I was cleaning my insert this morning and found a couple of pieces that looked like lava rock. Very light and airy. Sounded almost metal when the shovel hit them. Any idea what this is from?
Happy Thanksgiving!

 

[stoveliker]

Could be clinkers. Happens with some wood or bark. Mineral remains after burning the wood fuses together into this.

It's normal - for some types of wood. Nothing to worry about.

 

[brenndatomu]

This ^ ^ ^

 

[peakbagger]

Yup, its specific to wood species, stove or boiler configuration and how its run.

 

[NickW]

I've had more and bigger clinkers this year... like 1 1/2"×6"×8" sheets of it! Been burning some punky honey locust during the day - almost has to be from it. Was a yard tree someone gave me. I seem to get more clinkers from "yard" tree's versus "woods" tree's.

 

[Kominar]

I had lava-like clinkers right after the beginning of the cold season (November?) - was quite alarmed when I cleaned out the ashes after the first week and found this:

Alas, since then I haven't found a single one! - and I'm burning the same wood pile, in the same insert at similar settings (perhaps a bit hotter)... so where they came from remains a mystery. I haven't heard of others who start off their fire season with clinkers. All I can think of is that I may have had some lighter, fungus-digested deadwood in those early loads.

 

[SpaceBus]

If I go long periods without removing the ash in my cookstove the ashes get hard and packed tightly together. It breaks apart fairly easily. I burn spruce and fir pretty much exclusively in my cookstove, so that could be part of what's going on. I don't really mind unless it takes up part of the refractory when I remove it.

 

[bipsic]

Looks a little bit like a coprolite (google it)

 

[stoveliker]

I think clinkers appear when the mineral content of the wood is higher. Was this the top wood in the stack? Sand blew on it?

 

[Kominar]

I think clinkers appear when the mineral content of the wood is higher. Was this the top wood in the stack? Sand blew on it?

Good point... and no, it was covered inside the shed, and pretty clean. I like the mineral theory, but haven't been able to connect it to anything obvious in those loads of wood.

 

[stoveliker]

I see clinkers with certain types of wood, and if I burn very hot. So I think it's something in the contents (e.g. minerals) but it also needs to be above a threshold temperature.

In any case, it's not a problem. Scoop them out and deal with them as any other ashes.

 

[zmender]

^^ +1 on temperature correlation with those things

 

[Osage]

I think clinkers appear when the mineral content of the wood is higher. Was this the top wood in the stack? Sand blew on it?

I have been cutting in some deadfall the past couple of years that is close to the road. The wind blows the dust across the area. I have more clinkers with this wood than ever before.

 

[Draughts15]

Found some of this last night. Had a large piece stuck to the bottom of the stove and had to pry it up.. It broke into some smaller pieces. I also thought it was metal. I've been burning some of my odds and ends 24/7 and haven't cleaned the ashes out for a few days. I've been scraping the coals and ashes to a pile in the front before a relight.