Toby Newell
Member
- Messages
- 1,635
- Location
- Surrey
But yes, the gelling might help the bonding, or it might reduce the air spaces within the fibres. Great building material though.
Yikes I was hoping it would be quicker than that! Do you know that from first-hand experience?You probably won't know how much insulation effect there is until next winter. It will take months for the cork and hemp to fully dry...
Right I’m definitely not planning to spray it down at all like you might for standard sand + NHL mortars. Also idk if the knuckle / fingernail tests are appropriate in this situation given the natural flexibility of the densely packed bioaggregates?Ideally it's at least knuckle hard rather than needing to be nail hard before the next coat (you can't dent it easily with your knuckle, but still scratch it with your nail). The more the underlying coat has finished shrinking, the less chance of cracking in subsequent coats though...
And the final insulation gain only comes when the entire wall is fully dry, which is the slow bit once all the plastering is finished. Hemp and cork will both hold onto water longer than a sand aggregate but make the plaster partially self-tending while it carbonates.
Looking good! That stone is lovely but plastering is obviously for the best.View attachment 12262
Tonight’s progress. Second and third batches of hot mixed hemp lime and cork definitely came out better (less sloppy, much easier to work on the wall), although I think the second batch got too hot and might have actually combusted the hemp? If that’s even possible? I swear some of the clumps of hemp were coated in a grey fine ash-like dust! And it smelled a little smokey as well. I think the hemp all stuck to the bottom and got burned from the lime slaking intensely above it.
Yes it is somewhat fun but it would be more fun if it weren’t so backbreaking mixing it with a Hoe in a big metal bin…I have no idea about the real world mechanics, as I said, in hot slaked lime the hemp wood will start to decompose, I am not sure whether this would be bad, or desirable, maybe the gelled exterior of the chivs forms a better bond with the lime matrix. Someone out there should know, someone must have conducted tests. I would of thought the insulative properties might suffer, but I could be totally wrong. Must be fun to mix! Like a large chemistry set.
Yeah it’s always bitter sweet to cover it up, as it does look gorgeous when carefully flush-pointed and brushed back. But having a warmer, more energy efficient building has to take precedence for us.Looking good! That stone is lovely but plastering is obviously for the best.