SlipCasting

This is a step by step tutorial on how to slip cast. Slip casting can be useful for making multiples of one object and to make casts that are hollow on the inside. This tutorial is demonstrating how to slip cast porcelain in an already existing plaster mold easily and efficiently. For  a tutorial on how to make a plaster mold please refer to the "Plaster Mold Making" tutorial for more information.

Below You will find images of the materials needed to complete this tutorial. The materials needed are as follows:

Plaster mold
Large Rubber Bands
Paper or plastic coffee cup
Clay Sponge
Clay Cutting Knife
1 Gallon Porcelain Slip Ware (can be purchased at The Standard Ceramic Supply (http://www.7ceramic.com/)

1. Turn your one gallon of Slip ware horizontally and roll back and forth for 5 minutes to get the slip well mixed. You can also shake the gallon up and down but keep in mind it will be heavy.

2. Take the empty plastic/paper coffee cup that you gathered from the materials list and fill it up with slip from the 1 gallon container. Once you have done this place it aside for now.

3. Get your mold ready by making sure the inside is clean and dry. Match up the two halves of the molds by making sure the pinholes are aligned. This will ensure a sealed closure and no leakage when slip is poured into it. This is a mold of a snow man and pumpkin that was casted from plastic toys. Intricate molds and pre-made molds can also be purchased at ceramic supply. 

4. When the two halves of your mold are together fasten them with the large rubber band. Make sure they are nice and snug. This will keep the two halves together and further ensure no leakage.

5. Once you have placed the rubber band around your mold and secured it, flip the mold hole up.

6. Take the coffee cup filled with slip and pinch the edge of the cup to make a nice pouring spout. This ensures no spillage and that the slip will flow out of the cup nice and smoothly. We are doing this because the pour hole in our molds are not very large and we want to decrease the amount of spillage.

7. Pour slip into the mold nice and slowly. Fill the mold until it is almost to the brink. 

8. Once you have finished pouring slip into your mold you must wait for a certain amount of time for a desired thickness to build along the walls of your mold. Below is a timing chart you can refer to for desired thickness. While this is happening you will realize that the slip is getting lower and lower. This is happening because as your slip is building up on the inside of the mold its literally sucking the liquid slip into the mold walls thus resulting in the lowering of the level of slip.

10 mins=1/16 inch thick
15 mins= 1/8 inch thick
30 mins= 3/16 inch thick
40 mins= 1/4 inch thick

You want to stay in the range of 15 to 20 minutes for a decent thickness. For the sake of this tutorial i have allowed the slip to sit in the mold for 15 minutes.

9. You will begin to see layers of slip building up along the wall of the mold as you keep refilling it.

10. Once you have waited 15 minutes get prepared to pour out the excess slip into the coffee cup.

11. Begin to pour out your slip from the mold slowly. Make sure you are not completely flipping the entire mold over but rather tilting it so that the slip pours out from one side of the mold. This allows for cleanliness and ease of pouring. After you are sure all excess slip has been poured out the mold, tilt it against a wall for a couple of minutes to ensure that every last drop of slip has leaked out.

12. Place your mold hole down onto a piece of paper towel and allow for further drainage for about 10 minutes.

13. Tilt the mold to its side and allow for drying of the slip inside the mold. Wait approximately 2 hours before releasing the mold.

14. Once you have waiting for 2 hours you can release the mold to see if the casted piece is ready to fall out. You can determine this by seeing if the casted piece is slightly separating away from the walls of the mold. 

15. Remove the casted piece from the mold by pulling slightly on it. A good cast should allow the piece to just fall out. Do not pull too hard as this may tear the piece. If it is giving you trouble wait a few more minutes before trying again.

16. Trim away the bottom portion of your cast with the clay cutting knife. This excess piece is always trimmed away as it is build up along the mold where the reservoir was.

17. Wipe away the seam line and clean up the edge, bottom, and any other inconsistencies in the clay cast.

Your Finished! You now have a nicely casted of porcelain slip from your mold. Allow the pieces to completely dry before placing it in a kiln to be bisque fired. For more information on kiln firing techniques please refer to "Kiln Firing" 

http://lakesidepottery.com/HTML%20Text/Tips/Firing.htm