In the beginning....

So you think you want to make your own slip. Maybe it is because you want control, perhaps because finding ready made slip has become a burden or maybe it is a cost factor. Yes, it is less expensive to make your own, but you need to have a supplier close by who will sell you small amounts of chemicals and clays unless you plan on major production and can have your components shipped direct to you.

CLAY is heavy, it is not cheap to ship.

First some basic information about making your slip:

A gallon of good ceramic slip should weigh 14.5 pounds (plus a smidge). And it should have a gravity ratio of 1.75

To achieve this you should have a hydrometer and a scale. The gravity ratio is measured by the hydrometer and it tells you the amount of water in relationship to the amount of solids.

I strongly advise you to keep a journal an record each batch you make because there are seasonal variations in the ingredients and it is best to know what you experience each time you make slip. Record amounts, dates, and specific problems that may occur, like needing more deffloculant or needing to adjust the gravity. This probably sounds confusing to you, but I shall try to clarify.

Gravity is the ratio of water to dry ingredients. Ideal gravity is 1.75. A gallon of water at 70 degrees weighs 8.3 pounds. If your slip weighs 14.5 pounds you divide 14.5 / 8.3 and that equals 1.75 (with rounding). If your slip weighs less than 14.5 then it is considered light, so you need to add more dry ingredients. If the slip is too heavy, you add more water. To work with a smaller test amount, take a measuring cup and weigh the cup. Then weigh the cup full of slip. The difference from the cup full of slip and the empty cup will be the weight of the slip. One slip should weigh .9 pounds (give or take a couple grams)


Viscosity is how thick your slip is. You may want it thicker or thinner based upon what you are making. Hollow beads or small miniatures or Christmas items require a thinner slip. Larger items need a thicker slip. To change your thickness you do so by adding a deffloculant (Sodium Silicate) to make it thinner. You do not thin it by adding water. It could thro your gravity off. You should regularly measure you slip’s viscosity and can easily do this with a homemade viscosity meter…or you can purchase one.

To make your own meter, take a small 2 ounce plastic jar with a lid. Put a small hole (using a nail or screw) in the bottom of the jar and another hole, slightly larger, in the lid. Covering the hole in the bottom with your finger, fill the jar to the top with slip. Place the lid on the jar and put another finger on the top hole. Remove your finger from the bottom hole. Your slip should not drain out unless you release your finger at the top. Use a stop watch or clock with a second hand. Remove your finger from the top hole and time how many seconds it takes for your slip to flow out. Stop the timing when the flow is no longer constant but becomes drips. To gauge your own slip, you will first need to test someone else’s slip in order to establish the measurement of your own meter and be able to effectively use it for your own slip.

If your slip is too thick and the specific gravity is right, then you can add some deflocculant or other special additive to thin it -Very small amounts at a time.

So there you have it. To make good slip you need to keep two things in mind - a balance of both gravity and viscosity. Testing every batch you make, making it the same way each time, keeping records/journal of your results and any tests and adjustments needed and seasons/conditions will result in a consistent quality of your product.