Unlocking the Mysteries of Pyrometric Cones: A Ceramic Artist’s Guide

Hey fellow clay enthusiasts! Susan here, your friendly neighborhood ceramic artist, and today we’re diving deep into the fascinating world of pyrometric cones. You know, those little pyramid-shaped things that look like they belong in a Pharaoh’s tomb but are actually essential tools for any ceramic artist worth their salt (or should I say, glaze?).

Now, you might be thinking, “Susan, with all the fancy digital kilns out there, why are we still relying on these ancient relics to tell us when our pottery is done?” Well, my friends, it’s all about heatwork, and those little cones are the masters of measuring it.

What Exactly is Heatwork and Why Should We Care?

Imagine this: you’re baking a cake, and you set your oven to 350°F (175°C). But what if your oven is a bit wonky, and the actual temperature inside is different than what the dial says? Your cake could end up undercooked, burnt, or somewhere in between!

The same principle applies to firing ceramics. A pyrometer might tell you the temperature inside the kiln, but it doesn’t tell you how that heat is actually affecting your clay and glazes. That’s where pyrometric cones come in. They’re like tiny spies that go undercover in your kiln and report back on the cumulative effect of heat over time, aka heatwork.

Think of it like this: two runners might both finish a marathon in 4 hours, but one might have run at a steady pace while the other sprinted and rested intermittently. The end result is the same (they both finished the race), but the journey was very different. Pyrometric cones are all about understanding the journey, not just the destination.

Cones: Mimicking the Magic of Clay and Glaze

Here’s the really cool part: pyrometric cones are made from similar ceramic materials as your clay and glazes. This means they respond to heat in the same way your pottery does. As the kiln heats up, the cones gradually soften and eventually bend over.

Each cone is formulated to bend at a specific temperature range, and this bending point corresponds to the ideal heatwork for certain types of clay and glaze. So, by carefully observing which cones have bent and which haven’t, you can tell exactly how far along your firing is and whether your pottery is experiencing the right amount of heatwork.

Deciphering the Cone Language

Now, let’s talk about the cone numbering system. It might seem a bit confusing at first, but it’s actually quite logical once you understand the basics.

• The “Oh” Factor: Cones are numbered with a system that has a virtual zero in the middle. Cones to the left of zero have an “0” (pronounced “oh”) in front of their number, indicating lower heatwork. So, cone 04 is much lower than cone 4. Always say the “oh”!
• Team Captains: The bold-faced cones (018, 04, 6, and 10) are like the team captains of their respective firing ranges. They represent the most common cones used for ultra-low, low, mid, and high-fire ceramics.

Building the Perfect Cone Pack: Tips and Tricks

Using pyrometric cones effectively is all about creating a well-constructed cone pack. Here are a few tips to ensure you’re getting the most out of your cones:

1. The Three Musketeers: Always use at least three cones in your pack: a warning cone, a target cone, and a guard cone.
   • The warning cone (one cone lower than your target) lets you know you’re getting close.
   • The target cone is the desired heatwork for your firing.
   • The guard cone (one cone higher than your target) tells you if you’ve overshot your mark.
2. Synchronized Bending: Align all the cones in your pack with their spines facing the same direction. This ensures they bend smoothly and don’t interfere with each other.
3. Gravity’s Pull: Expose about two inches of each cone above the cone pack base. This allows gravity to work its magic and ensures the cones bend at the correct time.
4. The Perfect Angle: Set your cones at an 8° angle from vertical. The base of the cone is designed to help you achieve this.
5. Keep a Firing Journal: Record the behavior of your cone pack throughout each firing. This will help you track your progress, identify any inconsistencies, and make adjustments as needed.

Beyond Temperature: The Hidden Benefits of Cones

Pyrometric cones are more than just temperature gauges. They can also provide valuable insights into your kiln’s atmosphere and firing dynamics. For example:

• Bloating or blistering on your cones can indicate issues with your clay body or firing schedule.
• Cone color variations can signal uneven heat distribution within your kiln.
• “Hard-shelling” (where the cone’s surface melts but the interior remains solid) can point to problems with your kiln’s ventilation.

By paying close attention to these subtle clues, you can fine-tune your firing process and achieve more consistent, predictable results.

Resources for Further Exploration:

• The American Ceramic Society: https://ceramics.org/ – A wealth of information on all things ceramic, including technical resources and articles on firing.
• Digitalfire: https://digitalfire.com/ – A comprehensive online resource for ceramic artists, with a focus on glaze chemistry and firing.
• Ceramic Arts Daily: https://ceramicartsnetwork.org/daily/ – A great source for articles, tips, and tutorials on various ceramic techniques, including firing.

So there you have it, my friends! Pyrometric cones might seem like a small detail, but they play a crucial role in unlocking the full potential of your ceramic creations. By understanding how to use them effectively, you’ll be well on your way to achieving firing success and creating beautiful, durable pottery that will stand the test of time.

Happy potting!