Slip Decoration

[Columbine]

I have seen some really cool decoration using slip so that it looks like it's run on the clay. I think that what has been used is kind of a suction tool to run the slip on the pot. I was wondering how dry the pot should be when doing this? Can you put Porcelain slip on other types of clay? Another question somewhat related is, can you mix different types of porcelain say glacia and coleman?

[MatthewV]

Slip trailer (or rubber bulbs) work well for applying glaze or slips in a somewhat controlled manner.

 

Applying slips that stay on the body and don't crackle like mud flats: anywhere from freshly thrown to soft leather hard.

 

There can be minor differences with mixing different clay bodies. I have never seen huge problems from this but in the long run it is best to use one mixture. The same is true with having one body and a different slip. Most of the time they work just fine. There is some forgiveness, especially if the wall thickness isn't very thin (less than ~1/4").

 

Would I try a nice clay piece with an experimental porcelain slip? Sure. I wouldn't fill a kiln without seeing the results though. 

[Callie Beller Diesel]

As always, test for yourself. But I'm going to play devil's advocate and say that I put porcelain slip on stoneware all the time. They have to have compatible shrinkage rates, and as long as I keep the slip application to >1/4" I don't have issues. I'm not using your porcelains so I can't speak about those, but it's totally doable under the right circumstances. How moist or dry the pot should be depends not only on the clay type, but also on how the pot is made. If it's thrown thinly and the clay sucks in a lot of water, you're better off waiting until it's a lot stiffer to add any more slip. If it's not going to collapse with the slip, adding it while freshly thrown is the most efficient. It's that whole, annoying "it depends" answer. Test it and find out.

[Callie Beller Diesel]

Oh, and a drugstore ear syringe (or kids snot sucker) works pretty well for nice, goopy slip application, and is heaps cheaper than the fancy slip trailing bulb from the clay supply store. The fancy one is fantastic for fine lines, though.

[Celia UK]

As always, test for yourself. But I'm going to play devil's advocate and say that I put porcelain slip on stoneware all the time. They have to have compatible shrinkage rates, and as long as I keep the slip application to >1/4" I don't have issues. I'm not using your porcelains so I can't speak about those, but it's totally doable under the right circumstances. How moist or dry the pot should be depends not only on the clay type, but also on how the pot is made. If it's thrown thinly and the clay sucks in a lot of water, you're better off waiting until it's a lot stiffer to add any more slip. If it's not going to collapse with the slip, adding it while freshly thrown is the most efficient. It's that whole, annoying "it depends" answer. Test it and find out.

Diesel - re slip thickness did you mean >1/4" (more than 1/4") or <1/4" - less than 1/4"? Am assuming from the context of the sentence you meant less than - slip of the finger?

[Callie Beller Diesel]

Yes. Keep it under a quarter inch.

[Chris Campbell]

I often mix porcelain bodies when I have little amounts in unmarked bags (yes, I know I should mark them but ....) You have to default to the lowest firing temperature but mostly it works OK ... Not great but no disasters.

I often use my expensive porcelain as a slip over cheaper porcelain to get the bright white color. As diesel clay says, you have to keep it under 1/4 inch thick and the clay below should be no more than leather hard.

[dangerouspottery]

i have a large bucket of seived porcelain (same clay that i throw with). if i want to add some mason stain to some of this slip to make a decorating slip, is there a rule of thumb for slip/stain ratio?  (i've seen ratios for dry clay....but is there any guidance on adding stain to already-processed slip?)

 

thanks,

dp

[oldlady]

sorry to tell you that this is a "it depends" question.  which stain?  if you only want color for something you plan to paint on one pot, put some slip in a container and add some stain.   the finished color will be somewhat darker than what you see as you mix it.  if it is too pale once fired, add more color.  if it is too dark, add more slip.  it is like mixing paint for your house.

 

for a color you need to reproduce faithfully each time you mix it,  you had better be ready to test with very careful notes.

[perkolator]

Xiem bulb tool is pretty nice applicator.  comes with several sized tips and cleaning tools - I think it's much better than a drugstore snot sucker and it's less than $20, but those still have their place in studio.

 

One of my fav stand up slips is Arnie's Fish Sauce Slip, you can go REALLY thick

[spwhalen123]

I am setting up my own studio at home and I am experimenting with different clay bodies. I have already mixed around 5 gallons of slip using one, but I would like to experiment with a different body. I am adding stains to the slip. Basically, mine is a similar question as to whether this slip will be compatible with my other clay body. The slip was made with a gray low fire Laguna clay body, while my new body is Amaco white (#25). Both are earthenware and both I will be able to fire at cone 04. I am assuming that they have slightly different shrinkage rates but I am not certain. Any advice? I would like to use the 5 gallons of slip I have already mixed if possible.                                                                                              

 

Also I am just starting to mix stains with slip. I am not sure how the slip should look, and what happens to stain during the firing process. I have mixed a light blue with this grayish slip, and the slip has changed color slightly but has not become the color of the stain. Will I have to wait til after the firing to see if I need to change the way it is mixed or is there something wrong from the start? Should I mix the stain with water then add that colored water to the slip? Or should I mix the stain directly into the slip?

[oldlady]

mix the stain into the slip.  the slip you have might work.  might. work.  the stain is a pigment if that is more familiar to you.  what happens to it is that it becomes part of the slip you use on the pots.  

 

the color you see has nothing to do with the finished color.  slip is not like paint.  you do not see the color until the final firing.  

 

you are learning a skill.  try measuring some slip into a container.  put an amount of stain into it.  write the numbers down.  put some slip onto a test tile, a raw, unfired clay  with some texture on it.  that is test one.   add some stain to the container.  repeat the test tile.  that is test two.  continue until you are tired or you run out of stain.  keep records.  remember that you are learning a skill.  do not rush out with your best work and become disappointed when it does not do what your imagination thinks should happen.

 

i have one of the best books on slip decoration at home in my bookcase.  i just cannot remember its name or author right now.

 

if you saw the Clary Ilian reference, i have edited it out.  it is not exclusively a slipwork book but it is a great book to study.  has very thoughtful descriptions of shapes, shadows, learning your own style.

[Callie Beller Diesel]

You might check with the manufacturer's website or help line to see if they have shrinkage numbers available for their clay. They ought to at least have a total shrinkage number somewhere, and ideally they will have numbers on wet to dry, dry to bisque and mature shrinkage rates. In the absence of these, you can make a shrinkage gauge, or some other test for both of your clays and compare them. Sadly, there is no substitute for testing.