Post by mintcake on Mar 28, 2014 10:51:28 GMT -8
Hi,
For what it's worth, here are my results for the different ratios of local clay, charcoal, sand and sawdust that I spread on the inside of my 8-piece octagonal ytong heat riser. Very early days so far (2 burns only), but no sign of the ytong showing any weakening or cracking... time will tell.
These are all surface coatings, so are thin. The thickest is 2-3mm, I'd guess.
All are mixed with 1 part loosely packed clay (packing it hand-hard reduces volume by about 20%) and where there's waterglass that's 3tea spoons to roughly 100ml of clay.
The charcoal was ground to a powder, the sawdust was floor-sweepings after using a circular saw.
I looked at 2 things: how well it resisted scratches with a bluntish metal instrument and how it resisted a sharp object.
"Hard" here means about as hard as "mix 1" (pure clay) got. "Very Soft" means that I could rub it away hardly pressing with a bare finger (not even a finger nail).
(Test 9 is actually my gap filler/mortar mixture, which I didn't try as an insulative coating.)
I find the waterglass + sawdust result odd. I'd expected the
waterglass to increase the strength of the clay, but with the wood involved it seems that it hasn't.
Clearly 2 parts charcoal to one part local clay is too much.
The sand doesn't seem to make the mixture any harder, but does seem to reduce surface cracking. Since it's got negative properties as far as insulation is concerned I think I'll be leaving it out of my next test series: Bricks of different ratios of perlite, clay and charcoal.
For what it's worth, here are my results for the different ratios of local clay, charcoal, sand and sawdust that I spread on the inside of my 8-piece octagonal ytong heat riser. Very early days so far (2 burns only), but no sign of the ytong showing any weakening or cracking... time will tell.
These are all surface coatings, so are thin. The thickest is 2-3mm, I'd guess.
All are mixed with 1 part loosely packed clay (packing it hand-hard reduces volume by about 20%) and where there's waterglass that's 3tea spoons to roughly 100ml of clay.
The charcoal was ground to a powder, the sawdust was floor-sweepings after using a circular saw.
I looked at 2 things: how well it resisted scratches with a bluntish metal instrument and how it resisted a sharp object.
"Hard" here means about as hard as "mix 1" (pure clay) got. "Very Soft" means that I could rub it away hardly pressing with a bare finger (not even a finger nail).
Mix | Sawdust | Charcoal | waterglass | Sand | result |
| 2 | 0 | 1 | Y | 0 | Surface cracking. Hard, not easily scratched. |
| 4 | 0 | 2 | Y | 0 | Very soft |
| 6 | 0 | 1 | N | 1 | scratch-resistant, medium hardness crumbles. |
| 7 | 0 | 1 | Y | 1 | scratch-resistant, medium hardness |
| 8 | 1 | 1 | Y | 1 | Medium hardness. Crumbles easily. Poor adhesion. |
| 3 | 1 | 0 | N | 0 | scratch-resistant, medium hardness |
| 5 | 1 | 0 | Y | 0 | Soft, texture like soft chalk |
| 9 | 0 | 0 | N | 3 | Hard, resists penetration, but brittle. |
(Test 9 is actually my gap filler/mortar mixture, which I didn't try as an insulative coating.)
I find the waterglass + sawdust result odd. I'd expected the
waterglass to increase the strength of the clay, but with the wood involved it seems that it hasn't.
Clearly 2 parts charcoal to one part local clay is too much.
The sand doesn't seem to make the mixture any harder, but does seem to reduce surface cracking. Since it's got negative properties as far as insulation is concerned I think I'll be leaving it out of my next test series: Bricks of different ratios of perlite, clay and charcoal.
