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Slip and plaster mixing in general

Clay Slip

For the slip, you want a nice thick creamy clay and water mix. We found if you simply added water to sifted clay and stirred it up/ used a paint mixing attachment, it was still very lumpy and lots of the clay hadn’t soaked in. So, soaking the clay in a paste for a few hours/ overnight then diluting a bit more gives a better result. Given the wet summer we had, we noticed on our second clay harvest that there was some pretty slip-like goo sitting in the fields already, having had horses trampling on it in untold amounts of rain. We were able to slice off the top soil and use the sludge directly as slip – perfect.

Mixing plaster

We honestly tried shovels and all sorts to mix it up, but using the feet, either barefoot or with something like wet-suit booties is by far the easiest, most effective way, combined with flipping and turning the mix using the tarpaulin, to combine the ingredients. Get a few people in the pit with some decent tunes and soon everyone will be enjoying squelching around in the mud. It’s easiest to see and hear for yourselves rather than describe in words! So we made some videos, which are on this blog post: https://www.floweringelbow.org/2012/workshop/plastering-the-straw/

The clay needs a while to soak in the water and fully plastisise. We started out by mixing just the clay and water together then leaving it to soak for 4 hours or overnight and then mixing in the fibres later on. We streamlined the process later so we mixed it all together and then let it sit before putting it on the wall.

Adding all the dry ingredients first (earth, chopped straw, sand) and mixing, then adding a good amount of water to get the mix going, then adding a little as needed is how we approached it. It’s easier to add a bit more water if the mix is too dry than try and rectify a sloppy mix.

Only mix as much plaster as your pit (and stompers) can handle and that you can apply in the day/ next day – though the clay element of the plaster can be revived, the fibres can make it a bit smelly and start harbouring moulds etc if you leave it more than a couple of days. We found our little pit was just about right for batches of five 12-litre-buckets of earth with the accompanying 5 buckets of chopped straw and water.

The aim with the mixing is to get the fibres and clay combined well and evenly in a sticky consistency that keeps together. We declared the mix ready when it all held together in a big ‘sausage’ in the tarp’ and it appeared to be evenly mixed. It’s worth experimenting with how wet you like the mix for getting onto the straw.