5 Common Mistakes with Glaze Dipping, Chemistry & Firing Schedules (And How to Avoid Them)

As a ceramicist and studio teacher, I’ve spent countless hours exploring the world of glazes. There’s something so satisfying about dipping a piece into a smooth, vibrant glaze and transforming it into a beautiful work of art. But along the way, I’ve encountered my fair share of mistakes—some of which resulted in pots I was less than proud of. Today, I want to share five common pitfalls I've stumbled into when it comes to glaze dipping, chemistry, and firing schedules, along with practical advice on how to sidestep these issues in your own studio.

1. Over-Dipping Your Work

One of the most common mistakes I see (and have made myself) is over-dipping. It’s tempting to get a thick, luscious coat of glaze, but too much can lead to drips and runs, creating a messy finish.

How to Avoid It:

  1. Keep your glaze at the right consistency. Aim for a viscosity similar to heavy cream. If you find your glaze is too thick, thin it out with water gradually—about 1/2 cup per gallon is a good starting point.
  2. Dip for just a few seconds. Generally, a quick dip of about 3-5 seconds is sufficient for most glazes.
  3. Allow excess glaze to drip off before placing the piece on a kiln shelf.
💡 Hannah Mercer's Rule of Thumb: Always test dip a sample piece first. It’s a small investment of time that can save a lot of heartache later!

2. Ignoring Glaze Chemistry

Glaze chemistry can feel overwhelming, but neglecting it can lead to disastrous results. For instance, using incompatible materials or not accounting for the expansion and contraction rates can result in cracks or defects. How to Avoid It: 1. Invest time in understanding the basics of glaze chemistry. Key elements to familiarize yourself with include silica, alumina, and fluxes. 2. Use a glaze calculator to ensure your recipes are balanced. Websites like Glazy.org can help you find compatible glazes based on your materials. 3. Take notes on your recipes and results. Documenting your trials makes it easier to reproduce successes and avoid failures.

3. Skipping the Test Tiles

I once thought test tiles were a waste of time and clay until I had a disaster on my hands. I had a gorgeous piece all ready for its final firing, only to find that the glaze turned out completely different than expected. How to Avoid It: 1. Always create test tiles before glazing your final pieces. Small, simple tiles allow you to see how the glaze will behave without risking your best work. 2. Make at least three tiles for each glaze: one for a thin dip, one for a medium dip, and one for a thick dip. This way, you can see the full range of effects. 3. Label your tiles clearly with the glaze name, firing temperature, and any special notes.

4. Miscalculating Firing Schedules

Firing schedules are essential for achieving the desired results. I’ve had pieces come out underfired (still porous) or overfired (glaze ran off) due to incorrect schedules. How to Avoid It: 1. Follow your kiln's manual for guidance on firing schedules. Each kiln can behave differently, and it’s essential to get to know yours. 2. Use a pyrometer to monitor the temperature accurately. Trusting just the kiln’s internal readings can lead to discrepancies. 3. Allow for cool-down periods. Rapid changes in temperature can lead to cracks, so plan for slow cooling, especially for larger pieces.
Error Solution Best Practice
Over-dipping Dip for 3-5 seconds and thin glaze as needed Test dip on a sample piece
Ignoring glaze chemistry Use a glaze calculator and understand key ingredients Document recipes and results
Skipping test tiles Create test tiles for each glaze Label tiles with details
Miscalculating firing schedules Follow kiln manual and use a pyrometer Allow for slow cooling

5. Not Preparing Your Kiln Properly

An often overlooked mistake is not prepping the kiln properly. I’ve opened my kiln to find pieces stuck to the shelf or warped due to poor placement. How to Avoid It: 1. Use kiln wash on your kiln shelves to prevent glaze drips from fusing your pieces to the shelf. 2. Arrange your pieces carefully, ensuring there’s enough space between them for heat circulation. 3. Check your kiln’s venting system. Proper airflow is essential for even heating and preventing unwanted reductions.
What’s the ideal thickness for a glaze application?
The ideal thickness for glaze application usually falls between 1/32” to 1/16”. Aim for a smooth, even coating that doesn't run or drip.
How can I tell if my glaze is too thick?
If the glaze looks overly shiny or has visible streaks, it may be too thick. Thin it out and test it again.
Why are my glazes not adhering to the clay?
This could be due to a few reasons: improper bisque firing, incompatible glaze and clay body, or not cleaning the surface properly before glazing.
In my journey as a ceramicist, these mistakes have taught me valuable lessons. Each piece I create is clear proof of the trials and errors of my craft. By sharing these common pitfalls and how to avoid them, I hope you find success and joy in your glazing adventures. Remember, every mistake is an opportunity to learn and grow in your ceramic practice!