Keep on Stirring! The Importance of Proper Mixing when Glazing Pottery Sue McLeod

Glazes and glazing are finicky, to put it mildly. Every potter has opened the kiln to a kiln load of glazes that didn't turn out how they were supposed to. There are many things that can cause issues with glazes, but Susan McLeod suspected that one of the most common glaze issues in the studio where she works as a technician was insufficient mixing. So she did a little experiment to show students the importance of good mixing.

In today's post, an excerpt from the April 2026 issue of Ceramics Monthly, Susan shares the results of her experiment and reveals the ideal duration for mixing glazes! –Jennifer Poellot Harnetty, editor

A Stirring Experiment 

In order to show our studio users the importance of mixing well, I took one of our studio glazes and did an experiment. You can do this experiment with your glazes, too. 

• I chose our Sapphire Blue glaze, which contains 4% rutile and appears very different when it’s thin versus thick. 
• I used a stirring stick provided by our studio—a 11/2-inch diameter dowel. 
• The glaze bucket is a 30-gallon, gray plastic garbage can. The bottom isn’t flat—it has a hump in the center with a moat around it (you know the ones). 
• The glaze batch quantity is around 20 kg (44 lbs). 
  

I stirred the glaze for 10 seconds, going back and forth, side to side, front to back, over the hump, in the moat, clockwise, and counter-clockwise. It seemed like a fairly solid effort. 

I stopped stirring and quickly dipped a test tile, holding it in for 6 seconds. 

I immediately resumed mixing for another 20 seconds = 30 seconds total. I stopped, dipped another test tile for a 6-second dip, and started stirring again. 

This time I stirred for 30 more seconds, for a total of 60 seconds. This felt like a really long time. My goldfish brain started to get bored, but I kept mixing. 

When I finally got to 60 seconds, I dipped a third test tile for 6 seconds and called it a day. 

How Long Should You Stir? 

Figure 1 shows the fired results and a great visual example of the effectiveness of mixing: Left tile = 10 seconds, middle tile = 30 seconds, right tile = 60 seconds. 

As you can see, 10 seconds is definitely not enough time to bring all of those heavier particles up to the top. It’s very thin: too much water at the top of the bucket. 

At 30 seconds, it’s much closer to being well mixed, but when you compare it to the 60-second mix, you can see that it’s not quite homogenized yet. It’s a bit splotchy. 

At 60 seconds, the glaze is quite uniform from the top of the tile to the bottom. This is ideal. If you want variation with the thickness, you can do that intentionally using different application methods. 

After the initial mix, you generally won’t need to mix that much again throughout the glazing process, unless it’s a long glazing session. In between dips, 5–10 seconds of new mixing should be plenty. And yes, I do stir the glaze before each and every dip. It only takes a few seconds for the particles to start settling again. 

Just Keep Stirring 

So based on these results, at our studio, I recommend stirring each bucket for at least 60 seconds before glazing. The time can vary for different-sized buckets and different stirring devices. 

Tip: Find a 60-second tune that you can sing or hum while you’re stirring. The intro to Queen’s “Bohemian Rhapsody” is pretty close. And so is the chorus of “Dancing Queen” by ABBA. 

Now I have a visual example that I can show people when I suspect their glaze wasn’t mixed well enough. Seeing the visual results of this test is really helpful to demonstrate the importance of mixing well. 

Remember, 60-second stirring is only applicable if you DON’T have access to a high-speed mixer. With a high-speed mixer, it’s even more effective and much faster! But if you’re going old fashioned . . . Just keep stirring! 

the author Sue McLeod has been a studio potter since 2010 and worked as the ceramics studio technician at a community studio in Victoria, British Columbia, Canada, for 6 years. She now works full time from home, researching glazes in her home studio and teaching three online glaze courses: Glaze Mixing Essentials, Mastering Glaze Consistency, and The Art of Glaze Chemistry. She also runs a large, free, glaze-support community on Facebook titled “Understanding Glazes with Sue.” Read more ceramics articles and register for her online glaze courses at suemcleodceramics.com.