To thin one gallon of slip add a small amount of distilled water and stir. You can mix manually or use an electric mixer to get the desired results. Be sure to stir for at least 1 minute before you assess the thickness of the slip.

Note about the thickness of porcelain:

When ready to cast, porcelain slip should be a light creamy consistency. If you are casting little molds, slip should be thinner than normal due to the size of the pour hole and the piece. If you are casting very large molds the porcelain should be a little thicker than normal. If slip is too thick in a head mold or medium sized mold, you will get hesitation lines in your casting. In an open faced mold you may want the slip a little thicker.

If slip has been frozen:

Thaw slip, It will look like tapioca pudding when thawed (slip with lumps). Pour the slip into another container (like a 2 ½ gallon bucket) make sure you have all of your slip out of the jug, scrape off all porcelain on the sides and bottom of jug. Use a drill mixer or jiffy mixer until all the lumps are gone. Let it sit for 5 –10 minutes to make sure it does not thicken again. If it still seems a little stiff add a little distilled water and re-mix. Feel free to strain your slip after thinning and mixing to make sure your porcelain is free from any lumps or debris.

Old and thick slip:

If slip is old and very thick, don’t be alarmed by any mold that is growing on the inside of the jug, this is a natural occurrence which actually improves your slip and should be mixed in during your preparation for casting. (Old potters in China used old clays and the sons of potters would use the clays that their fathers had mined and they would be preparing clay for their sons. They never used the clay that was made during their generation.) Mix the slip first, paying careful attention to the sides and bottom of jug. It is much easier to mix if you empty it into another container, scrape everything out of the jug, then mix. Then you can make sure that you get all of the solids on the bottom. Mix porcelain well, either manually or with electric mixer. If you still need a thinner consistency, add distilled water and mix.