While sitting in the king's chair this morning, I was reading a 1917 book explaining to kitchen servants all about how to run an efficient kitchen in that era.  One of the things covered was coal stove management including types of coal, starting and maintaining the stove fire, and dealing with clinker.

The book had a comment that one way to deal with coal which formed a lot of clinker was to add oyster shell to the coal.  I'm not sure why this would help---since servants are well, servants, they didn't go into any science or details involved.  Oyster shells are primarily calcium carbonate so there might be some chemical action going on which at temp, causes clinker to be more like ash or something...or it might be an "old wives tale" that they are just repeating.

Anyway--I see that Tractor supply sells 50 pound bags for 10 bucks.  My coal doesn't seem to be producing much clinker so any test I did would tell little about whether it helps or not.  Just wondering if anyone had any thoughts, might have a handle on the chemistry involved assuming there is some, or just general comments.

Since a few people here have said their coal seems to make a lot of clinker, I was just tossing the idea out.  A handful of crushed oyster shell might (and that's a big "might") reduce clinker problems at a low cost.  Worst-case,  you have a bag of something good for the garden and chickens and 10 bucks less in your wallet.

Anyone ever heard of this or care to venture a guess as to why they suggest oyster shell as a solution?

 

I have heard of adding crushed oyster shells to the corn in a corn-burning furnace to affect the hardness/quality of the clinker developed in those stoves.  I believe that depending on the design, some corn stoves/furnaces have a clinker breaker and if the clinker gets too hard they have problems with that.  So I think it's probably a real thing, but I don't know any more about it than that...  -- Dave

Tractor Supply sells anthracite coal here abouts. That coal has less metallic impurity than the more common softer bituminous smithing  coal. It costs about $6.00 for a 40 pound bag, here. So they may be selling different coal near you.

Clinker composition contains a lot of metallic oxide. Perhaps the crushed oyster shell may be reacting with the metallic impurities to form metallic carbonates. (that is a surmise and may be wrong). The carbonate would probably be a lot softer and perhaps more crumbly than a metallic oxide.

SLAG.

I know in smelting iron ore you add limestone to displace iron in the slag to get better yield. But I'm not up on chemistry of stove clinker.  What book were you reading sound like a good throne read.