Fireplaces, Heating Stoves, Flues and Chimneys - brick mortar

I'm installing thin brick on an interior fireplace and I want my mortar to be stickier. I'm mixing 3 parts sand to 1/2 part thin set motar plus 1/2 part portland. To get this to stick to the brick it has to be wet and will not stick to my trowel. I'm applying the brick to a vertical surface. I also have som brick to install inverted. Any suggestions?

You need to use a mortar with a plastcizer in it, such as lime. SpecMix mortar has it, or you can make your own with a mixture of two parts sand to one part plastic cement.

Also, you never mentioned why the thinset was not sticky enough by itself. It will not fill in large gaps, however, and will shrink and crack if you try to use it like regular mortar.

For placing the brick inverted, make a framework of 2x4s that are about an inch below the surface you are applying it to. After you set a brick, you can insert a wedge between the 2x4 and the brick as you go along.