What is Specific Gravity and how do you measure it?

What is Specific Gravity

Specific gravity is the measure of how much water is in a glaze. It helps you calculate how much water to material you have in a given glaze or solution. If your glazes have a consistent specific gravity your glaze should look and act the same each time. If water evaporates from your glaze and you dip your piece it may look very different from what you are used to. Similarly if there is too much water content in your glaze it will also affect the color.

What should the specific Gravity of my glaze be?

Typically starting out testing your first glaze I suggest you make a 100 gram batch of glaze and add 80 grams or milliliters of water to your glaze. This is a good starting off point and it keeps your experimentation consistent. You can refine afterwords.

In General, for a dipping glaze, your specific gravity should be between 1.40-1.70. Each glaze is different and each person applies their glaze differently. Testing and adjusting the glaze according to your preferences is tedious but necessary.

Ways to Measure Specific Gravity

There are 4 ways to find the specific Gravity of your glaze.

1st Way Hydrometer method

Things you will need

1. Graduated cylinder (optional)
2. Hydrometer
3. Glaze, slip, underglaze etc

Steps

1. Take your glaze and fill the graduated cylinder if your hydrometer can not float in the bucket of glaze.
2. Put the hydrometer into the glaze and tap until it won’t be submerged any further
3. Take the hydrometer out and read the results.

2nd Way: Graduated Cylinder

Things you will need

1. Graduated cylinder
2. Scale to learn more click this link here
3. Glaze, slip, underglaze etc

Steps

1. Put your empty graduated cylinder onto the scale
2. tare your scale
3. take your glaze and fill the graduated cylinder up to 100 ml
   • 100ml of water is equal to 100 grams of water. Knowing this means that when you fill the graduated cylinder up to a hundred and divide by that number you will get your specific gravity.
4. divide the number you get by 100 and write that number down

3rd Way: Scale and Syringe method

Things you will need

1. Syringe
2. Scale to learn more click this link here
3. Glaze, slip, underglaze etc

Steps

1. Place the empty syringe onto the scale
2. Tare your scale (zero out your scale)
3. Fill your syringe to the 100 ml mark
4. place your syringe onto the scale
5. divide the number on your scale by 100
6. write that number down for the next time as this is your specific gravity

4th Way: Specific Gravity Cup

Things you will need

1. Specific gravity cup
2. Scale to learn more click this link here
3. Glaze, slip, underglaze etc

Steps

1. Put the specific gravity cup onto the scale
2. tare your scale (zero your scale out)
3. take your glaze and fill the cup
4. place the lid on top of the cup
5. Place the cup onto your scale
6. mark the number on your recipe

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