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phanhuyen12

a quick question about Process

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Do you use deflocculated slip, regular slip or magic water for joining.   ?

 

I have not tried deflocculated slip, just watched John Britt's video on You Tube on this and am considering it for a stiff slab project upcoming.  Are different processes better in different situations?

 

Some of my students get slabs too wet when using vinegar water, looking for a better way for them

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Generally I use a little wire brush made especially for this to score the surface to be joined, then regular slip made from the same clay. However if feeling lazy which is frequently, and the clay is too moist already I won't use anything, just join it together well with my fingers and wooden tools. 

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I use straight cider vinegar with a stiff brush (stiff as in tooth brush) to score and slip my hand building.  When vinegar is not available, I just use water or the nearest source of slip.  Thick is to wait until the shine disappears before joining the pieces and compressing the join.  At the "loss of shine" stage the moisture levels of the surfaces to be joined are approximately equal, and success is enhanced significantly.  

LT

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Magic water is a very mild deflocculating solution that seems to open up the surfaces to be joined by the same process of creating similar (and consequently repelling) ionic polarity of the clay particles, thus allowing the joining surfaces to intermingle better. Deflocculated slips have  two characteristics of interest - 1) obviously a deflocculant is involved, similar to magic water, and 2) the deflocculation allows a lot more clay to be incorporated into the same volume of slip, making for a stronger and drier (less shrinkage) joint. Vinegar, a mild acetic acid promotes adhesion between the surfaces of the parts to be joined. Which is better depends on who you ask. I take it a step further by using a paper clay slip made with vinegar rather than water. Plain water and the paper fibers will quickly turn to black mold if kept in the wet state, but vinegar instead of water will effectively pickle the paper fibers so you can keep a tub of it ready to immediately use as needed. And the vinegar does double duty for adhesion.

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It really does depend on the clay you're using. The porcelaneous stoneware I used to work with needed slipping and scoring. When I switched clays, I found my new red stoneware didn't like the slip at all, and cracked all to heck. It needed less moisture to work properly. I'd suggest a bit of a test to see which method works best for you. 

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it depends on what I am doing.

To me the real key is how well do you scratch the surface. Esp with sculpture. I score really well with a fork. That kinda creates the slip right there. Just water and a coil has always worked for me. 

I think students getting their slabs too wet is part of the learning process. 

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I used slip, then vinegar slip for years, then I found magic water. The ^6 stonewares that I used worked very well for me, but I noticed the biggest difference in the student pots. First they had fewer cracks in bisque happening, second they had cleaner corners and joins than with the slips, lastly these areas seemed to take glazes well, with little in the way of roughness, or discoloration that I would occasionally have with the slips. Now regular water has always worked well with me with scoring and working the water with a stiff brush, but I use magic water in my shop also. 

 

best,

Pres

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