Friday, August 24, 2012

A Low Rent Mortar Sprayer

(When I first posted this I used the word "coupling" to describe a 1-1/4" bushing. I apologize and hope I didn't cause anyone any grief. You need a 1-1/4" threaded bushing . So far, despite that I've had to make a few adjustments, this sprayer has worked well for me. A little electrical tape around the threads of the bottle make for a tighter, more permanant fit.Thanks.)

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.

Update 3/7/13: This sprayer has been working well. I’ve been using it to spray some experiments with burlap-crete. However, when I attempted to replace the air gun with one (I thought was) just like it, I found that the threads of the bushing inside the PVC fitting were too short to engage those on the air gun. Though both were purchased at Harbor Freight, the air guns were slightly different. Which means not every air gun will work in this system without some additional retrofitting. I had to grind away some of the thickness of the PVC with a Dremel tool, and also cut the little curled ring off the new air gun to make it work. Also, I’d used a Clorox bottle at first because I happened to have one. A gallon Concrete Bonding Agent jug is sturdier, is a tighter fit, and generally works better.



  1. "Then the brass coupler is screwed onto the tip of the air gun to hold it in place."....only part I'm confused about. What kind of brass coupler?

    1. I apologize for not answering your question. I was not getting notifications of comments. I would have answered immediately. One problem I have on this blog is not always knowing what to call things -- often go in search of "anything that might work" and don't know what to call it once I find it. Looking at the sprayer right now, I'd say the removable tip of the air gun is what is holding it in place. I had to use a dremil tool to reduce the thickness around the hole a little to make that work. Once again, sorry about the long delay in responding.

  2. hello
    my sprayer not work...
    most of the air go up in the gallon and let the cement bubbles same lava in a vulcano.

    just a litle air come out with a spray of concret. most of concret run out of the hole down to the ground.

    what i do wrong ?
    do you have a picture from inside the bushing ?

    thanks for any help
    Peter from thailand

    1. So sorry for not responding to your question. I was not getting notifications for comments and so didn't know you had a problem. The only thing I can think of related to your issue with mortar spraying out of the top is that the holes are not perfectly aligned. Or perhaps your air compressor is more powerful than mine. Mortar will run out of the hole and the sprayer needs to be tilted back between sprays. You've probably moved on to other projects. So sorry I couldn't respond sooner.