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When is ideal to apply slip to a surface?


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So I want to use a slip to make a certain texture on my vases using straw brushes (before the bisque fire, so I can paint on vases later on). It is a pretty thick layer. So the question is - on what stage of clay it will be the safest to do this? Bone dry or leather hard? I mean it does an additional moisture to the vase so it can lead to additional cracking, I am very afraid of this.

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exactly right.   if you really think about what a coating of slip is, you can see that it is just an addition of the tiniest bit of clay.  the color doesn't count, it doesn't add to the volume.  you could get the same result by rolling out an itsy bitsy bit thicker clay,

to apply to a wheel thrown piece, do it while the surface has just lost its sheen and use a big mop brush if coverning a huge amoune of the clay.   dollar tree makeup brushes are terrific mops.  turn the wheel on slowly and keep the mop wet enough so it doesn't drag.

if it starts to dry out, just use a spray bottle for adding water as it spins.

Edited by oldlady
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Posted (edited)
On 6/20/2024 at 4:57 AM, oldlady said:

exactly right.   if you really think about what a coating of slip is, you can see that it is just an addition of the tiniest bit of clay.  the color doesn't count, it doesn't add to the volume.  you could get the same result by rolling out an itsy bitsy bit thicker clay,

to apply to a wheel thrown piece, do it while the surface has just lost its sheen and use a big mop brush if coverning a huge amoune of the clay.   dollar tree makeup brushes are terrific mops.  turn the wheel on slowly and keep the mop wet enough so it doesn't drag.

if it starts to dry out, just use a spray bottle for adding water as it spins.

Thank you. I'm doing coil building so the vase is fully made after a couple days of work, between sessions the vase is covered in many plastic bags so it almost doesn't dry,  so it is not as moist as freshly made wheel thrown piece, but I don't think it's such a big problem, right?

Edited by pojkoo
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Coating with slip - even a rather thin coat - adds moisture to the ware, as the OP notes.
Adding slip to the inside (a bowl, for instance), when the ware's almost dry enough to trim, I'll slip the inside, then wait for it to dry some/again before trimming.
For the outsides, I'll add the slip right after trimming.

Slipping "too early," the ware can sag/slump a bit - too wet!
Slipping "too late" - idk, I believe I've erred to the early side only (so far). I wanted the slip and the ware to have a chance to equalize in terms of moisture, then dry together.

Still good to be cautious though!
Test on your least favorite piece that's about the same size, thickness, material, etc. as your target wares?

Edited by Hulk
- when
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I appky slip at trimming time  i spritz the pot inside and out after trimming then apply slip with a mop brush. My slip usually has a bit of sodium silicate in it, more liquid with less water content so shrinkage less .

Left too dry before applying, it can survive a bisque but bloats away fro. the pot on a glaze fire...

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