Sealing Tiny Pond with Clay (How to Tamp)

Hello all! I recently dug a small pond and am struggling to seal it. The bottom is very clay-ey with a little bit of sand.

I dug out a couple spots in the chicken area to try and control the flooding and give the chickens something fun. I was all ready to tamp it down to seal it but found a bunch of clay at the bottom. I tried tamping the stuff at the bottom and then I tried smearing some on the sides and tamping the walls, but the clay just fell right off.

I ended up just smearing the clay around all the sides and letting it dry (like pottery, right?) and it dried hard but it cracked and won't hold water. I tried repeating this process to see if another layer of clay would eventually crack in different places and seal up the cracks but it's still not holding water after three or four iterations.

I am struggling to figure out the proper amount of moisture to have in the clay to seal it and how to tamp it without the clay just falling off. Do the sides of the pond need to be extended to be shallower? That might make tamping easier. I tried filling the hole to keep it from drying out but it drained pretty quick on me. I also tried covering the hole with a large piece of cardboard to try and make the clay dry slower but it is still cracking.

Does anyone have any ideas for how I can get this to seal?

Thanks!

Here we line the pond with a mixture of bentonite and soil and then cover with a layer of soil.

Suggest looking up gleying a pond.  There are a number of permies posts on it as well as else where.

C. Letellier wrote:Here we line the pond with a mixture of bentonite and soil and then cover with a layer of soil.

Suggest looking up gleying a pond.  There are a number of permies posts on it as well as else where.

Thanks for the suggestion! I just found this thread on gleying ponds: https://permies.com/t/80/3409/Gley-technique-sealing-ponds-dams

I'm wondering if I put the poopy chicklet/duckling bedding in the pond and maybe mix it around with the clay if that wound help reduce the cracks enough to keep water in there for longer. And when the ducks are old enough to go outside I can get them to poop in the ponds and it could help seal them more over time (I dug out several small ponds and started experimenting with the smallest one to get the technique down). Another option would be to try and find someone in the area that could give me some manure, but I like the thought of using what I have. The next question would be does it matter what type of bedding - would straw be better than pine shavings for this? Could I also use leaves to create the seal in the pond?

My understanding is that the sides of a clay pond do need to be pretty shallow, but that is more to do with the clay flowing than the initial sealing - it will tend to slump down hill as livestock tramp in it.
Here's a picture of a (pretty dry) dew pond for reference of typical angles used:

dry dew pond in UK

source

Your clay has to many impurities for sealing.  If you feel up to putting in the effort you can clean the clay and then use a purer form for sealing.  Look up purifying cleaning natural clay for making pottery.

You're doing great. I think you're almost there. Did you tamp the clay down real good. Stomp on it real good.

https://permies.com/t/39241/finally-pond-sealed-clay

You mix stuff with the clay will certainly help. If you have brush and the pond is dry you can also light the pond bed on fire that will cook the clay and seal it.

You're clay seems good enough you just need some elbow grease or some cows to tamp it down real good. If you have a bag of lime laying round go head and mix that up too.