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Post by cassius on Jul 24, 2019 0:50:38 GMT -8
Here's my first rocket stove. It's a mixture of 80% perlite, 20% Portland cement. You can see bands where the cement has settled to the bottom a little, or the composition of different batches was slightly different (all added when wet so should be ok). It's a few days old and needs more time to cure before I burn out the cardboard tubes. Right now, the outside seems a little crumbly, and doesn't look very good. So: Has anyone tried coating a stove like this with a layer of fireproof cement, like this stuff? www.screwfix.com/p/flomasta-fire-cement-2kg/9588VI think it could give the stove a better appearance and greater durability. The real question is, when should I do this? If it's coated before the concrete is truly dry, I imagine it will lock in moisture and make it more susceptible to cracking.  |
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Post by wiscojames on Jul 24, 2019 17:47:33 GMT -8
I'd coat it now rather than later. It will be more crumbly later. The moisture will find its way out through cracks regardless. I think coating it will strengthen it enough to use it for some time, as long as you're not rough with it, cooking or moving it.
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Post by cassius on Jul 24, 2019 21:53:21 GMT -8
I'd coat it now rather than later. It will be more crumbly later. The moisture will find its way out through cracks regardless. I think coating it will strengthen it enough to use it for some time, as long as you're not rough with it, cooking or moving it. Thanks, sounds good. It's not exactly falling apart but I'm aware that the Perlite mixture isn't as robust as it could be. Plus it looks kind of messy. Any advice on how long I should leave it before giving it a short test burn to burn out the cardboard chimney former? |
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Post by wiscojames on Jul 25, 2019 9:14:26 GMT -8
Wait until you can't wait no more.
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Post by cassius on Jul 25, 2019 9:41:25 GMT -8
Wait until you can't wait no more. Fair enough. Saturday then probably  As it happens, fireproof cement can withstand heat of 1250C but is a bit rubbish in the rain. The external stuff is several times more expensive. It doesn't need to be fire cement, could be heat resistant paint, plaster, PVA, whatever. Just something to keep the outside from degrading and neaten it up a bit. Anyone had the same issue and got a good solution? |
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Post by gadget on Jul 27, 2019 15:41:51 GMT -8
Hey Cassius,
I don't know if this would work for your application but I found a perlite mix that works good for some applications. It does not use portland cement. Its basically this;
1 part clay powder(high alumina), 3 parts perlite. I mix really well dry then slowly add just enough water till all the perlite is coated with clay. You want minimal amount of water. Compact it into desired shape. Then after it is dried completely, fire it with and acetylene torch till it forms a ceramic coating. This happens fairly fast. Basically you get the dried perlite/clay core with a thin ceramic shell that handles fairly high temperature and is pretty strong - depending on the composition of the clay.
I don't know how strong it would be for a large monolithic structure but it is looking like a good insulting layer for a heater I am building that should handle wood abrasion . Best part it is very cheap.
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Post by cassius on Jul 28, 2019 0:08:09 GMT -8
Hey Cassius, I don't know if this would work for your application but I found a perlite mix that works good for some applications. It does not use portland cement. Its basically this; 1 part clay powder(high alumina), 3 parts perlite. I mix really well dry then slowly add just enough water till all the perlite is coated with clay. You want minimal amount of water. Compact it into desired shape. Then after it is dried completely, fire it with and acetylene torch till it forms a ceramic coating. This happens fairly fast. Basically you get the dried perlite/clay core with a thin ceramic shell that handles fairly high temperature and is pretty strong - depending on the composition of the clay. I don't know how strong it would be for a large monolithic structure but it is looking like a good insulting layer for a heater I am building that should handle wood abrasion . Best part it is very cheap. Thanks Gadget, that sounds like the kind of thing I need. What I just did yesterday is mix pure Portland cement as a paste and cover a patch of the outside that was looking ropey. No idea how it will hold up. Subsequent research suggests that probably wasn't smart, but live and learn. |
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