mixing clay into cob

Hello all. I'm attempting to make a cob "slip" to mortar together my bricks for a heat riser. I hear a 50 50 ratio is good. Some bricks cemented very well and some horribly. The ones that came apart had the texture of rough wet sand. I have a feeling I didn't have enough clay. I added pure balls of clay I found and it seems impossible to knead it into the mix, I can only make the clay into smaller and smaller pieces even after soaking it for a long time. In my area I seem to either have pure sand or pure clay. Should I dry the clay and pound it to dust or what should I do to incorporate it better and ultimately have a more effective mortar? Thanks!

If you let the clay dry completely (the thinner/smaller the pieces are, the faster this will be), it will easily crush to powder. Almost-dry clay will be very difficult to crush.

Alternatively, working wet clay with more water and letting it soak will also work. Again, thinner/smaller pieces will finish much faster. It somewhat depends on how wet most of your clay currently is.

Have you tried a drywall mixer? The paddle that you put into your electric drill and it spins?

I was surprised a few weeks ago when I was watching some instructional videos from American Clay on YouTube.

The guy recommended mixing the clay for like five solid minutes, and THEN letting it sit overnight. That's a whole lot more than I would have anticipated. But if anybody would know, he would.

So I'd say try that: try mixing it with power equipment, for way, way longer than it seems necessary, then let it sit 24 hours. Works for the pros.

I have used a drywall mud mixer on clay. The material that I'm processing,  has already been dug up from trenching work around houses.

 Some water rises to the top when it sits or is transported.