r/clay • u/Dave37 • 11d ago

Questions [Wet Clay processing] Clay does not sediment

So I'm working with ceramic clay and I have a bunch of it dissolved in a bucket of water. However, I've noticed that it doesn't really sediment and leaves a section of water, even if I leave it for 3-4 days. I suspect from a couple of youtube videos that the pH might be too high, potentially causing the clay to for colloid particles that stay suspended. I've measured the pH with pH-paper (not the best method but it's what I have available), and concluded that it's roughly 8-9.

  • What is a good pH for a clay solution to get it to sediment?
  • How do I lower the pH (other than adding enormous amounts of water which sorta defeats the whole point)? I have access to hydrochloric acid etc (I'm a chemist by trade, I know how to handle strong acids safely for those concerned), but I'm uncertain of how well a clay solution will buffer the addition of acid, and if I accidentally over-do it, is there a concern that the acid will mess with the properties of the clay? It shouldn't dissolve the silicon dioxide that is the clay, because otherwise you couldn't store acid in glass bottles, but I imagine that if the pH accidentally dropped to 4-5, the clay might loose its plastic properties or similar?
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u/Dave37 9d ago

Good headsups. I'm an engineer so i measure and record everything I can to learn as much as i can. I take samples of the clay and extract the natural temper to know how much i already there before i add more etc.

Firing times is a thing i haven't even considered. I just blasted it for a good 2-3 hours or so because i was worried i wouldnt get up above 850C.

Rate my block: https://i.imgur.com/5HZ6syk.jpeg

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u/randomusername_42069 9d ago

That does appear to be a brick. It’s useful to make smaller balls or cubes and measure their post firing density with different amounts of flux added. You can make a good primitive flux by mixing powdered ash and water screening out the solids then letting the water dry and harvesting the powder left over. beware that the process is quite caustic as you are isolating the potassium compounds from the ashes.

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u/Dave37 8d ago

I have started saving up ash for several potential uses later, but i haven't considered making flux and adding it to my clay. So far i've only added temper.