Should I Make Colored Slip Or Make Slip From Another Clay Body...

[oceancity]

Hi,

 

I want to achieve the look of Standard Ceramic Supply's Brooklyn Red Cone 6-8. It's a brick red color at cone 6. 

 

The clay body I work with is a white stoneware and it is the staple clay at the studio I go to. I love the look of the red clay. Personally, I can't feasibly buy 100s of pounds of the Brooklyn Red and so I figured I could create pieces in my white stoneware and use brooklyn red clay as slip so I get the look I want. 

 

Would it be better to do something like create a colored slip with my original white clay body that matches the look of the Brooklyn Red? Or would it be too hard to get the color I'm looking for?

 

Basically, this isn't something I'm familiar with and I've been researching for a couple hours and can't really get a good answer to my question 

 

 

Another question about slip: Should I sieve the slip even if it's just for dipping or brushing on to pots? Will sieving it affect the clay other than making it smooth?

 

 

Thanks!

[curt]

Have you tried it? I mean dipping your white stoneware in some of that slip? Shrinkage needs to be the same, otherwise you will get cracking in the slip cover, either at the drying stage or firing stage. And that is a deal breaker (unless that is the look you are going for!).

 

A far more reliable path is to use your body clay to make the slip, and then colour it with the right amount of red stain or iron oxide and/or whatever other colorants are necessary. Then you will know the slip fits your clay body right out of the box. Just tinker with the colour until you get it right. Or better yet, improve the colour!

 

Sieving (or power blunging) is recommended for good application, and for eliminating lumps. But be careful not to introduce air bubbles. However, if the slip is properly deflocculated this should not be a big issue. No other effect from sieving that I know of, as long as you don't use a sieve so fine that you start removing raw materials from the clay!

[ayjay]

It seems like a lot of hassle compared to just buying the right clay, (and checking what temperature the studio fires to).

[Magnolia Mud Research]

Using clay A as the base body and wanting the appearance of using clay B is actually easier than most posters have claimed, at least for me.

 

I often use a dark red clay body as an overcoat on a buff or white clay body.  The pots are designed to be "not fussy", or "gingerbreaded".  Stamped maybe, but when I cut them from the wheel, I am done, except for foot trimming or sponge cleanup. 

 

The pot is thrown.  I then take a bucket of slip made from the red clay body and slather it on to the pot with either my hand or a soft wide brush.  Thin coat to begin with.  When the sheen is gone, I compress the coating with a soft flexible rib.  A second coat of slip is then added and any organic markings are made. Evaluate when the sheen is gone for the need of a compression pass and additional slip. I generally apply only to the outside of the pot, but it works when the inside is to be treated with red. After all this is completed, the pot is dried further and the foot ring trimmed as needed.  If the foot ring requires a coat of the red clay it is applied now using the same concept:  Thin coating followed by compression. Additional Coats and compression are added  until the final appearance is achieved. 

 

By applying the slip at the time of throwing followed by compression, the interface between the two clays becomes bonded just like the two layers of marbled clay are bonded.  Unless the two clay bodies are significantly different there will not be enough intergranular stress to initiate cracking between the layers.  If you wait until leather hard or bone dry, the shrinking differences are maximized as are the probabilities of cracking, spalling, and delamination.

 

When handbuilding, I use the same process.  Produce slabs, coat the slabs with the coating and compress with a hand roller and/or rib.  Both sides are treated if necessary.  After assembly, areas are examined and treated with the coating using the same thin application and compression sequence until the appearance is acceptable.  

 

The slip is thick, but spreadable with a brush. 

 

N.B.  If you try to compress before the sheen is gone, you will just move the slip around and compression against the substrate will not occur.   On thrown pots, you may need to support the form to compress the slip layer,  just as you would for compressing while throwing.

 

 

LT

[oceancity]

Thanks for your responses! 

 

I haven't tried anything yet because I wanted to see if it was possible first. And I didn't want to buy the red clay if I couldn't use it.

 

It's more work, but for me it makes more sense.

 

Magnolia Mud: Thanks for your response!! This makes me feel more confident that the red clay will work for me. I just need to check that the shrinkage is close enough. 

 

If you don't mind answering another question...I was wondering if you deflocculate the slip you use?

 

Thanks!

[oldlady]

adl, why would you imagine that the slip needs defloculation?  where are you getting your information?

 

magnolia mud has laid out a wonderful way for you to achieve your goal.  the explanation is spot on.  if it needed anything else, someone who gives such good, detailed info would tell you.  try the suggestion and be pleasantly surprised.

[Magnolia Mud Research]

 

 

 

 

Magnolia Mud:

If you don't mind answering another question...I was wondering if you deflocculate the slip you use?

 

Thanks!

 

 

Nope!

 

I just add water and stir with a stick, or sometimes with a hand blender.   Since most of my coatings are applied to thrown ware, I am aiming for a slip that is about the same as, or thicker, than the slip that is scraped off the surface following a pull.  I generally get a thicker, because I get bored with stirring.   I keep a bucket of slip covered.  Usually it has a big wet shrinkage crack across the bucket surface, but the wet stuff is smears easily, so that is what I use. 

 

LT

[oceancity]

 

 

 

 

 

Magnolia Mud:

If you don't mind answering another question...I was wondering if you deflocculate the slip you use?

 

Thanks!

 

 

Nope!

 

I just add water and stir with a stick, or sometimes with a hand blender.   Since most of my coatings are applied to thrown ware, I am aiming for a slip that is about the same as, or thicker, than the slip that is scraped off the surface following a pull.  I generally get a thicker, because I get bored with stirring.   I keep a bucket of slip covered.  Usually it has a big wet shrinkage crack across the bucket surface, but the wet stuff is smears easily, so that is what I use. 

 

LT

 

 

 

Thank you! I really appreciate your detailed responses! 

[Callie Beller Diesel]

I've been doing a lot of white slip over red clay lately. I've not had any flaking issues, and I haven't been compressing. If you're reclaiming a lot of your pieces with slip on them, I'd actually warn against deflocculating your slip. Too much deflocculant in the reclaim will really mess with you when you try throwing it again.

[oceancity]

I've been doing a lot of white slip over red clay lately. I've not had any flaking issues, and I haven't been compressing. If you're reclaiming a lot of your pieces with slip on them, I'd actually warn against deflocculating your slip. Too much deflocculant in the reclaim will really mess with you when you try throwing it again.

 

 

I hadn't thought of that. Good point! Thank you!