Sideways

Joining bricks horizontally is difficult. Well, actually, cleanly joining bricks horizontally is difficult. Is it a tool problem? Is it a material problem? Is it simply a silly thing to attempt?

I know from experience that mortar falls off the brick when it is turned sideways. Unless the mortar is really wet, and then it gets sloppy. So, I thought of using a two-step process: first, join the bricks with something really sticky, like resin. Then, pack mortar in from the top, using the resin as a base. The trial I made, though, is still very messy on the bottom.

The underside of the test piece. The resin is uneven and the mortar is showing through in some places.

Here you can see the resin on the bottom and the mortar on top.

I decided to try using plaster as the adhesive.
I thought I could trowel it on accurately, but it was still really messy.

Then I thought that if I had a surface against which I could wipe the trowel, it might produce a sharper edge. I modelled the overlap of the bricks (which is a strange wave shape) and put together a trial tool with cardboard cut on the laser cutter.

A very rough test tool.

PVA glue is supposed to make mortar stickier, so I tried the tool using regular mortar with added PVA. The clean edge worked, but it wasn't sticky enough- the mortar still fell off when I tried to press it to the other brick. So I tried plaster again, with the tool, but the plaster stuck to the tool as well. And it stuck to the trowel, so even if the tool was made of metal that wouldn't help.

I think what I might have to do is go back to the previous system, but instead of putting the resin right at the bottom of the joint, I will put it closer to the middle. This means I will have to pack in mortar from both sides (from the bottom as well- that will be another challenge) but it means I will have more control over the finish of the joint. And what I can do is build a tool that allows me to apply the adhesive from a tube without wobbling. For the first test I was just using a caulking gun. I needed two hands to operate it and it still was shaky. If I build something like the extruder I was working on last fall, I can perhaps extrude the adhesive with one hand and move the brick with the other.