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STNJ1000

recycling commercial casting slip

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Hi, my question is about the role deflocculants play in slip and how they do or do not effect recycling:

I am using a commercial /i.e, storebought, /i.e. premixed stoneware casting slip. I've been trimming my casts, the pour spouts that are in the molds,  as well as some dud casts that deformed when demolding. The result is that I now have a bunch of bone dry clay scraps that I would love to recycle back to casting slip. My understanding is that the bucket of slip I bought has the proper amount of deflocculant and water in it off the shelf. What happens to that deflocculant as my casts dry? If I throw my bone dry shards in a bucket of water, is the deflocculant still in there?  Do I need to add more deflocculant? And how do I know how much water to add?

I've avoided making my own slip from scratch because all the stuff I've read about deflocculants and specific gravity seems intimidatingly technical. Will it be just as technical to recycle storebought slip, or is there a simple way to go about it?

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4 hours ago, STNJ1000 said:

Will it be just as technical to recycle storebought slip, or is there a simple way to go about it?

In all likelihood you will have to adjust the slip containing recycled clay which means having a grasp of measuring both viscosity and specific gravity.  You would also need a mixer that can run for hours to recycle the dry scrap back into the slip. I don't know what kind of volumes you are making, if it's just the odd piece then it's probably not worth the effort, if you've got hundreds of pounds to recycle then I think it would be worth while reading up on slip casting. Measuring viscosity and specific gravity isn't difficult.

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16 hours ago, Mark C. said:

If you have a mixer next time do not let it dry out and mix it when its still wet/damp as the good stuff is still in it then.

Does this mean that the "good stuff" (are you talking about deflocculant?) evaporates away or is lost in the drying process? How is that so? I was under the impression that it was best to recycle clay from bone dry, rather than wet, as it absorbed water more evenly. 

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Yes that can be true but when we ran a huge slipm operation we aleays tossed the wet stuff back into mixer as it was still very wet and mixed well. The materiual is still in the clay but you will as Min said have to recalculate the slip again will dry reclaim as you now need water and that will thro off the mix. You will need to learn how to make slip and how to measure the slip (slip hydrometer and ford cup to measeure flow rate )If your opoeration is small than just buy slip and forget the rest. We had 150-200 molds and produced thousands of aroma therapy lamps for a large company (United Naturals) Its a nation wide outfit. Now its all made in China.That business was a side business for me at the time.(90s-early 2000s)

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I read somewhere that you can up to one third dried slip to new slip. 

I allow it to dry thoroughly, then bash it (dust mask) and add it to a very small amount of water, just enough to cover - tall narrow vessel rather than wide.

Then add back to the slip. 

I often make slip by drying clay and adding water and a couple of stops of sodium dispex.

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