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Plaster for wedging table


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There is several different type of tile backer board now.  Some of them aren't very absorbent,  I would do some research on them before I bought one.   Avoid the original Hardibacker board it is some kind of pressed fiber that doesn't hold up to water.  I  think they have a new one that is for the exterior that is water resistant.   I have also seen one that is some kind of treated sheetrock material.   Even the concrete backers can have added materials to them.   I bought some that was concrete but thinner, lighter and stiffer for a mural,  but I don't think it would be good for clay work.   Denice

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  • 2 weeks later...

I am so glad I didn't try and do the whole top of my supply bench! Just a 22" square by 2" high was really tough! definitely a two person job. Of course my mixer broke right as I was done "soaking" the plaster so I had to quickly plunge my arms into the two buckets and mix by hand. Nearly a compete loss. When I heaved one of the buckets up to "pour" into the mold, the plaster just stuck in the bucket because it was already setting. I had to scoop it out with my arms and flatten it in the mold as best I could. You can see in the picture where it didn't "flow" very well and there are air pockets along the sides. It will take several weeks to dry but I think it'll be ok.

OMG, what a mess, I made. Next time definitely an outside job! But, I like it. It's much bigger than the last one which I've been using for years:

 

 

IMG-2834.JPG

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I learned this from an architectural plaster master: You can over mix plaster, causing it to set too quickly. First sift the plaster into the water, stir it very gently- as little as possible- to make sure it's all wet. You may not need to stir it at all after sifting if it's not mounded up above the water. Then let it sit for 5 minutes. That will allow the water to penetrate. Then use your mixer to mix it just enough to get it smooth. It won't take much after letting it sit. The more you mix the faster it will set.

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I make my slabs out side,  I throw a plastic drop cloth over the side walk.  When I was a dental lab technician I learned to use the coldest water I could.  This gives you more working time,  I also have started making two smaller slabs.    I am getting older and it's getting harder to move the slabs around.    Denice

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I prefer 12 inch square concrete stepping stones for wedging.  one side for white clay, other for not white clay.  The concrete does not dry the clay as much as plaster which helps keeping the wedged clay moisture homogenous.  For drying I use 12 inch terra cotta flower pot saucers.  These do a good job of drying clay, stack easy, and are not as heavy as plaster - never had problems with porcelain picking up iron from the terra cotta.  Both of these tools can be hosed down for cleaning when needed, and quickly return to a workable dry stage after being hosed. 

LT 
 

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47 minutes ago, Magnolia Mud Research said:


I prefer 12 inch square concrete stepping stones for wedging.  one side for white clay, other for not white clay.  The concrete does not dry the clay as much as plaster which helps keeping the wedged clay moisture homogenous.  For drying I use 12 inch terra cotta flower pot saucers.  These do a good job of drying clay, stack easy, and are not as heavy as plaster - never had problems with porcelain picking up iron from the terra cotta.  Both of these tools can be hosed down for cleaning when needed, and quickly return to a workable dry stage after being hosed. 

LT 
 

Excellent ideas! I especially like the flower pot saucers for drying slop.

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+1 to above comments.

And

Put your long sleeved rubber gloves on before you start measuring, then when you need to plunge your hands into the bucket, you can do so without risk.  Plaster can be irritating to skin.  I don't use a mixer or stirrer, only my gloved hands, that way I can feel for lumps and know it is properly mixed.

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As I have limited space, I have recently created a 2/3  cover for my concrete/canvas wedging table. Made of painted plywood from a kitchen renov. it is easy to change from dark to white clays. In the first few days I was challenged wedging on it as the surface is so smooth. However, now I have become used to it and can wedge as well as on the other toothy surface.

I may end up coating the entire table with plywood not as it has much less dust and washes quickly with a wet sponge.

 

best,

Pres

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(use the coldest water I could.  This gives you more working time,  I also have started making two smaller slabs.    I am getting older and it's getting harder to move the slabs around.    Denice)

This is the best tip of the day as it really works

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