We started out with a stiff mix....sand/lime/clay/sawdust/water. Was too sticky and stiff. Hard to work. Adding water helped.
Then we tried a wetter mix later that also had a higher sand ratio, plus the addition of straw...Worked much better...not as sticky and the straw smoothed right in like it was not there when worked with a float. I applied it shovel by shovel.......dropping each load with force so that it spread like a cow patty, which eliminated having to thin it to the desired level first. We are spreading it about an inch thick...give or take. The flat shovel worked really well as the first spreader...using the back of the shovel to smooth. Then my wife and older boy finished it with a wooden float and then a steel float. It is unlike cement in that it has much more body so adding it bit by bit seems to work much easier than squashing down a big load that sits too high. It acts more like a stiffer mortar than poured cement.
Monica's Note:
When coming up with a recipe with for clay plaster or for an earthen floor, the two things to consider are final product ~ does it work? and ease of application ~ is it pleasant to work with? Generally, the mix that is hard to work with will not produce a good final product.
So, we've found a mix that is easy to work with. We will have to wait and see if it cracks, etc... although in this case we aren't too worried about cracking, because it's easy enough to repair on an earthen floor. (Also, don't forget to wet down the subfloor with a garden hose before adding the earthen layer, to get a good bond between the two layers.)
Here's the recipe we are currently using. Everything is measured by 1 gallon bucket and makes a good amount for the mortar mixer we are using. Our mix is higher in lime than a standard earthen floor, because we happen to have 5 big barrels of lime putty sitting around, so we're putting them to good use.
20 sand
3 lime putty (type s)
3 water
3 chopped straw (approx 3" long, leftover from trimming the straw bales)
1 clay putty (same consistency as the lime putty)
1 sawdust
*Added Note: This mix had too little lime. It does not hold up to wear. We will add a second layer with more lime later.
