We’ve all heard the sound pottery makes when it hits the floor, but did you know pottery can “ping” as well?
It’s true! In fact, pinging pottery is more common than you’d think, though it’s not necessarily a good thing.
If you’re looking to learn more about pinging, also called “crazing,” you’ve come to the right place.
Crazing is a term used to describe the physical effects of pinging, which is really a misalignment between the bisque clay piece and the glaze applied over it.
The small spider cracks that network across a glazed piece are called crazing, which occurs because there is tension between the bisque body and the glaze itself.
Pinging pottery is not a good sign, especially if you meant for the pieces to be food safe.
In this article, we’ll point out the common causes of pinging in pottery, as well as what you can do to fix it. In some cases, repair of these tiny cracks is not possible, but there are changes you can make to help your next pottery piece avoid pinging.
Let’s get started. Here are 7 reasons why your pottery
Why is My Pottery Pinging?
There are many reasons for pinging pots, but here are a few common ones.
Most pottery pings are caused by the unhappy marriage between the bisque-fired clay and the glaze over the top of it.
If the bisque beneath the glaze is contaminated with oils or some other type of substance, the glaze is not able to fully adhere to the pores of the bisque. This can create a barrier between the two, which leads to the glaze separating from the bisque beneath.
Improper Amount of Glaze
When you hear a pottery ping, it’s not the sound of the clay body, but rather the glaze instead. Applying too thick of a layer of glaze on the clay body can actually cause moisture to be trapped within the layer between the clay body and the glaze. This is the root cause of those tiny cracks.
Because pinging is a glaze defect, different glazes may react differently. When the glaze shrinks more than the clay body, typically during temperature extremes, tension occurs and must be released. These small cracks are the sign of a much larger problem with your glaze.
Glaze and Clay Body Combination
Choosing the type of clay you use is important for your project, but so is the glaze. If the glaze and the clay body are not compatible, then you’ll have issues from the very beginning.
One common pottery issue is that potters use the wrong combination of glazes and clay. In theory, a glazed surface should adhere to any clay, but that’s not always the case. Newly developed crazing lines can occur even on glazes that are compatible with the clay beneath.
If the amount of moisture in your glaze is too high, this could cause the crazing to occur. Moisture can cause pockets to form between the clay body and glaze, which could cause glaze fall issues. Commercial glazes with lots of water should be stirred thoroughly before they’re applied to prevent crazing.
As a general rule, you should also let glazes dry completely before throwing them in the kiln. If pots are not allowed to fully dry with glazes applied to them, then the pores will hold water and cause cracking.
Kiln Opened Too Early
It can be hard to wait for the kiln to cool down, but after firing, let your kiln cool down as it should.
The first time you open the kiln too early, a mixture of various temperatures can occur, which could cause your pieces to crack. Pots and pieces within the kiln need to fire at a consistent rate in order to allow the glaze to adhere correctly.
Pottery Cooled Too Quickly
Pinging pots are like alarms, signaling that crazing might occur because of the heat that’s quickly escaping. When you fire a pot or a bowl, you need to let the piece heat up slowly. Going too far out of range of the temperature of your piece can cause crazing.
The same can be said for cooling your pot, bowl, or another piece. Glazing requires as much of a gentle increase or decrease in temperature as bisque firing, so keep this in mind as you operate your kiln. A slow cool is best.
Movement During Firing Cycle
Ceramics, like a delicate cake, shouldn’t be jostled when they’re in the kiln. Even bumping a table against the kiln can cause a crack to occur. If the glaze is in a liquified state and attempting to adhere to the clay body beneath, any movement can create issues.
Crazing, or pinging, can actually occur for years and years after a piece has been fired. This crazing typically occurs when temperatures change drastically, or the humidity varies greatly.
Even if you don’t hear the pinging after the piece has been removed from the kiln, it might still ping years down the road. Crazing can occur at any time in the piece’s life.
Did you know that some potters actually set out to achieve crazing? These cracks can create a unique pattern that is not easily replicated. In order to achieve this crazing effect, potters will fuse melted glass to the outside of the bisque, then glaze over it with a white or clear glaze.
However, this creates a significantly weaker piece overall, since the crazing is still a response to thermal expansion and/or rapid cooling. Each crack can harbor bacteria, so typically pieces with intentional crazing are not functional ware. They can technically be a functional piece for anything else besides food.
How to Prevent Pottery From Pinging
Diagnosing the cracks in your pottery from the pinging you hear is the first step in understanding why your glaze didn’t adhere correctly. Moving forward, there are a few things you can do to prevent crazing in the future.
Here’s a quick reference list of the actions you can take to prevent pinging/crazing:
- Check that you followed the glaze recipe instructions
- Increase one or more of the following elements: lead oxide, silica, clay, talc, zinc, alumina, and/or boric oxide
- Decrease feldspar
- Substitute borate frit for high-alkaline frit
- Substitute lithium feldspar for sodium feldspar
- Apply a thin(ner) layer of glaze
- Fire at the proper cone
- Increase your firing temperature
- Reduce the soaking period
- Lightly sponge the rim before glaze firing
- Ensure the glaze dries out completely before firing
- Cool your ceramics slowly
- Check to see if the glaze and the clay type are compatible
In some cases, even if you think you did everything right, a piece may still experience pinging. The important thing is to keep a log of what all you’ve done in order to narrow down the culprit behind the pinging. Doing so might seem tedious, but it’s one of the only ways to truly figure out why your pottery is pinging and addressing that issue head-on.
Frequently Asked Questions
What does pinging pottery mean?
If your pottery pings, it means the glaze and the clay beneath it did not adhere properly during the firing cycle. There are many reasons why this might happen, most of which we discussed above.
Why does fired pottery ping?
Fired pottery pings because the glaze over the top of the bisque fired clay is shrinking too much compared to the bisque itself. Really, it’s a glaze defect. The tension there is released by the pinging, which can actually lead to microscopic cracks in the glaze.
What causes crackling in pottery?
Crackling in pottery is caused by a few different things. It could be that the moisture content of the glaze is too high, which creates a separation between the glaze and the bisque base underneath. Crackling also occurs when the temperature changes drastically.
Can you buy crackle glaze?
Yes, it’s possible to purchase crackle glaze in order to achieve the cracking effect. Glaze crackle is a really cool concept, but you should note that using this type of glaze will make your piece incompatible with food or drink.
Spinning Pots lists a glaze crackle recipe as well as other information on glaze crackles. You can also search Spinning Pots’ website for how to make crackle pottery.
How do you tell if glaze crackle cracks have occurred?
One easy way to detect spider cracks is to leave coffee sitting in the piece overnight. In the morning, when you go to pour the coffee out, any cracks that are there will be highlighted by the dark liquid. To ensure proper food safety, don’t use any pots or bowls that have crazing.
You can also use dyes such as India Ink. Lakeside Pottery details how to remove crazing stains from pottery. There are many pictures of crazing on the Lakeside Pottery website as well.
Is a fired glazed surface vessel food safe if it has crazing?
No, cracks are not food safe. In fact, even the smallest cracks can house a multitude of bacteria, so it’s best not to use or continue using food-safe vessels that have crazing.
We hope you’ve found this article on the many reasons why pottery pings are useful. Hearing your pottery making noise on its own can be startling, but now you know what to expect if it does happen. You also now know how to prevent pinging in the future, so you’re well on your way to becoming a better potter.