An Untraditional Method to Using Porcelain Casting Slip

When I use porcelain casting slip, instead of pouring it into a plaster mold, I pour it onto a plaster slab. Once the slip has set and I can touch it without getting it on my hands, I cut around the edges using a scalpel and lift it off. I will then cut, fold, and shape the casting slip into whichever form I desire.

This is what it looks like when I pour slip onto plaster. I usually wait until the shine fades before I start to lift it off the plaster and manipulate it. These are the two casting slip recipes I use depending on the temperature I would like to fire to.

Cone 6

OM 4 ball clay ……10lbs

EPk …………………….5lbs

Grollegg ………………5lbs

G200 Feldspar …….5lbs

Neph Sy ………………5lbs

Flint (Silica) …….7.4 lbs

The total 5 gallon batch is 17025 grams with 2 gallons of water and 68 grams of Darvan. Begin with 2 gallons of water and add 43 grams of Darvan. Add the dry materials in order and blunge in between each material. When the mixture gets too thick add more Darvan. Add about 5-10 grams until the total Darvan is 68 grams. Weigh 50 mL in a syringe, it should weigh between 80-90 grams. If its too heavy add more water and re-weigh.

Cone 10

EPK …………………625 grams

Tile 6 ……………….625 grams

OM4 ball clay ….1250 grams

Flint ……………….1250 grams

Custer Feldspar …625 grams

Minspar ……………625 grams

The total batch is 5000 grams. Add water to the consistency desired.

When Adding Other Materials…..

Sometimes I like to add other materials in or on the casting slip depending on what I am making. I have tried mason stain, under glaze pencils, glue, ink transfers, floor polish, watercolor paints, food coloring, and sharpie markers. This is what I have discovered….

Combining Mason Stain with Porcelain Casting Slip

When adding mason stain to porcelain casting slip, you first want to test the amount of stain to the amount of slip. To figure out the color I want I start with 59 grams of slip/3.5 grams of stain. I usually go .5 grams higher and lower as well using the same amount of slip to get more of a variety of colors. Don’t forget to label each one with the amounts you use.

Applying Transfers onto Fired Porcelain

Wintergreen transfers onto fired porcelain works great but don’t forget to flip the image before you print or make copies on a xerox copier! That’s a very important step. Next, put the wintergreen oil on the back of what you would like to transfer and place it onto the fired porcelain. Then scratch the paper using a tool with a hard, dull tip like a pencil. Lift a little corner of the paper up to check if your image is there before lifting the whole thing just incase you need to do some more scratching.

Once the wintergreen transfers are on the porcelain, it is very hard to get it off, unlike sharpie marker. Sharpie can almost disappear with denatured alcohol if the timing is right.

The materials I used for this image is mason stain, wintergreen transfers (the lighter text) and sharpie.

Here’s a link to see what the bottle that I get looks like. http://www.rainbowblossom.com/blog/2014/11/12/potpourri-how-to

Adding Other Color Besides Mason Stain….

If you are not planning on firing the porcelain but still want it to be a certain color, try watercolor or food coloring. The slip can still be a true color but watercolor and food coloring are much cheaper so you can have more room to experiment.

Looking For A Binder?

Glue and floor polish can be great binders. Floor polish works really well as a binder with dry materials when you are not planning on firing. Depending on how much floor polish you add the consistency can go from clay-like to slip-like. Also, the more floor polish that is used the more glossy it will look when it dries.

Each of these pieces I used floor polish to add texture. You can see the range I got from adding different amounts of floor polish.

I use glue when I already have the slip made and plan to fire the object. These paper clips were made with casting slip, Elmer’s glue, and string. After they were fired, the string would burn out and I would be left with a very fragile and hollow paper clip.