On February 18th, Rovin Ceramics hosted a free glaze mixing demonstration. With the large interest in this event, we wanted to share with you some of the information we presented.
Mixing your own glaze can be fun, economical and allow for customization, which can help you get that specific glaze you've been chasing. It is important to note that measurement and data collection will be crucial in maintaining consistency. First you will need some tools and materials:
You will also need a selection of dry materials. If you are new to glaze mixing, we suggest you find a simple glaze recipe in a magazine or book to get started.
ORDER OF MATERIALS
The order in which materials are added to a glaze can make a huge difference in the performance of the glaze. While the order will vary depending upon the recipe, it is important to stick to a schedule of adding items that absorb water first, then adding the other materials later. Working this way will help in hydrating all the materials and keeping everything in suspension.
This is a great way to start:
- Plastics (clay)
- Colorants & Opacifiers (oxides/carbonates/stains)
Left: glaze mixing. Right: Pouring glaze into a sieve.
- Fill mixing container with water. If the amount of water is unknown, make a best guess and keep track of how much water is used for next time.
- Carefully weigh all materials and label each one to keep track.
- Slowly add your materials to the water while mixing, following the order listed above.
- After all materials are added, pass the glaze through a sieve. This will help the materials absorb water, break-up chunks, and remove unwanted organic debris.
- Check the specific gravity to help adjust the water content.
- Adjust water content if necessary but keep track of all water additions to help you for next time.
- Let the glaze sit overnight before remixing and using (this allows all the materials to fully hydrate).
Left: Tools for glaze mixing. Right: Measuring specific gravity
Specific gravity is a measurement of how dense a liquid is in comparison to water. Water has a specific gravity reading of 1. When glaze materials are added to water, the specific gravity is increased because the materials are heavier than water. Tracking specific gravity helps keep the glaze consistent.
Measuring Specific Gravity
- Place a graduated cylinder onto a scale and tare your scale to 0.
- Pour 100 ml of glaze into the graduated cylinder.
- Divide the weight of the 100 ml sample by 100 to get the specific gravity.
- Desired specific gravity will be determined by the glaze recipe. Aiming for a specific gravity of 1.5 is a good place to start.
For a printable version of this information click here.