This is an effort to make and use a simple, inexpensive mortar sprayer.
I’m using it with my Harbor Freight 2 hp 125 PSI air compressor.
The sprayer is made from a 1.42 gallon Clorox bottle, a 1-1/4” PVC threaded bushing and plug, a Harbor Freight air gun, and a brass coupler. It was simple to make, easy to use, and worked well spraying a very wet mix of three parts sand to one part Portland cement.
As you can see in the photos, the bottom is cut from the bottle to make a funnel. Then the PVC bushing screws onto the Clorox bottle. It's not a perfect, tight fit. You can still turn the bottle, but the threads mesh enough for the coupler to hold on. I didn't glue the bottle to the bushing because I wasn't sure how the bottle would hold up and thought I might need to replace it quickly. It held up fine, though, for this first experimental effort.
The plug screws into the bushing just enough to wedge the threaded tip of the air gun between the bottom of the coupler and the bottom of the plug, and a hole is drilled to push the air gun through the side of the plug. I think I used a 13/32 bit. It needs to be a tight fit. Then the brass coupler is screwed onto the tip of the air gun to hold it in place. Exactly opposite this hole I drilled a slightly larger (15/32) hole. There is probably 3/4" between the end of the brass coupler and the spray hole.
And that's it.
I used the bottle to scoop mortar out a wheel barrow. Tilting the sprayer back slightly prevents the mortar from leaking out of the spray hole until you're in position. I was usually 12 to 18 inches from my target, sometimes closer. I would jiggle the sprayer a little to keep the mortar sliding down. The sprayer clogged once in the beginning because the mortar was too thick. Otherwise I was able to move pretty fast.
Spraying is much easier and faster than daubing.
I'm spraying mortar over papercrete. I sprayed several layers over a section of wall. I'll see how it cures before adding more layers.