Differences Between Pottery and Porcelain

In general, the term ceramics (陶磁器, tōjiki) refers to both pottery (陶器, tōki) and porcelain (磁器, jiki). However, numerous differences exist between them.

Table of Contents

• 1. Difference in Clay Color
• 2. Difference in Manufacturing Process
• 3. Difference in Glaze and Firing Temperature
• 4. Difference in Texture
• 5. Difference in Heat Conductivity
• 6. Difference in Usage
• 7. Difference in Care & Handling
• 8. Summary of Differences

The Difference Between Pottery and Porcelain In general, the term "ceramics" refers to both pottery and porcelain. However, when closely examining these two, numerous differences become evident. Due to their distinct properties, the methods of production, applications, and handling techniques also vary accordingly. Let's delve deeper into the differences between pottery and porcelain.

1. Difference in Clay Color

Both pottery and porcelain are made from clay. While both types of clay have a certain plasticity and harden when dried, their raw materials—and thus their colors—differ. Pottery clay, known as "potter's clay" (陶土, tōdo), is often colored due to the presence of various minerals. For instance, Karatsu ware (唐津焼, Karatsu-yaki) clay contains iron-rich red or brownish earth, while the Daidō clay (大道土, Daidō-tsuchi) used in Hagi ware (萩焼, Hagi-yaki) may appear beige or ochre yellow. Shigaraki (信楽, Shigaraki) clay is often gray.

The color of potter's clay results from the presence of organic materials, trace amounts of iron, and carbonized plant roots or wood fragments. This impurity-laden composition gives it its natural earthy tones. Because it is derived from soil, pottery is often referred to as "earthenware" (土もの, tsuchi-mono). On the other hand, the clay used for porcelain, known as "porcelain clay" (磁土, jido), is typically white and contains very few organic materials. For example, the porcelain clay from Arita (有田, Arita) and Amakusa (天草, Amakusa) is predominantly white. When composed mainly of feldspar or quartz, it can be nearly pure white. Porcelain clay originates from porcelain stone (陶石, tōseki) and kaolin, making porcelain fundamentally different from pottery. While pottery is "earthenware," porcelain is often categorized as "stoneware" (石もの, ishi-mono) due to its stone-derived composition. Thus, pottery and porcelain can be clearly distinguished by their raw materials and the color of their clay.

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2. Difference in Manufacturing Process

Both potter's clay and porcelain clay contain essential components such as clay minerals, feldspar, and silica. However, the ratios of these components differ:

Clay Composition Table

Material	Clay Content (Molding)	Silica (Glass-forming)	Feldspar (Flux + Glass-forming)
Potter’s Clay	50% (Soil-derived)	30%	20%
Porcelain Clay	30% (Stone-derived)	40%	30%

Clay content affects workability. Higher clay content results in greater plasticity, meaning the clay is softer and retains shape more easily. Conversely, lower clay content results in a firmer, less malleable material. Potter’s clay has high plasticity, making it easier to shape, whereas porcelain clay is less plastic and somewhat firmer.

This distinction affects the way pottery and porcelain are crafted. For example, when shaping a tea bowl, potter's clay tends to be made slightly thicker and later trimmed after drying. If made too thin initially, the rim might sag due to its own weight. In contrast, porcelain clay, being more rigid, allows for thinner walls from the outset with minimal trimming after drying. If made too thick, trimming can become cumbersome. These differences in workability directly influence the shaping and handling techniques for pottery and porcelain.

 

3. Difference in Glaze and Firing Temperature

Both pottery and porcelain are glazed before firing. However, since their clay bodies have different levels of heat resistance, the glazes used for each must also be adjusted accordingly.

Pottery clay is typically fired at 1,000–1,200°C, whereas porcelain clay requires a higher temperature, generally 1,200–1,300°C. As noted earlier in the composition chart, porcelain contains a higher proportion of glass-forming components.

Since porcelain clay has more glass-forming minerals, it requires higher temperatures and longer firing times to achieve proper vitrification. Consequently, porcelain demands more heat energy overall during the firing process.

What happens if the same glaze is applied to both types of clay? Suppose a glaze melts at 1,100°C and is used on both pottery and porcelain.

On pottery, the glaze melts properly and adheres well to the surface.

On porcelain, however, where firing reaches up to 1,300°C, the glaze over-melts, leading to defects such as excessive dripping, adhesion to the kiln shelf, or unintended color loss, potentially rendering colored glazes transparent.

To prevent such issues, potters select glazes that match the specific heat tolerance of each clay type.

For instance:

- Pottery clay with a fire resistance of 1,100°C should use a glaze that melts at 1,050°C over 8 hours. This lower temperature requires a glaze with a higher proportion of fluxing agents, such as ash, to promote melting.

- Porcelain clay with a fire resistance of 1,300°C should use a glaze that melts at 1,250°C over 12 hours, with a higher proportion of refractory materials like kaolin to prevent excessive melting.

Additionally, glazes are classified based on their heat resistance:

- "Strong glazes" (強釉, kyōyū) have higher heat resistance.

- "Weak glazes" (弱釉, jakuyū) melt at lower temperatures.

Due to these differences in heat resistance, it is essential to carefully select and apply glazes suited to either pottery or porcelain to ensure proper firing results.

4. Difference in Texture

Pottery and porcelain have distinct tactile qualities. Since both are usually glazed, the best way to compare their raw textures is by touching unglazed areas, such as the foot ring (高台, kōdai), which makes contact with the surface it rests on.

Pottery has a porous, rough texture. Because of its microscopic pores, its surface feels slightly grainy to the touch.

Porcelain has a dense, smooth texture. Unlike pottery, porcelain clay vitrifies completely when fired, resulting in a glass-like, silky finish.

Light Transmittance and Hardness

Pottery is non-translucent due to its porous structure, similar to natural stone.

Porcelain is translucent, allowing light to pass through its body. Holding a thin porcelain piece up to light reveals a faint glow, indicating its ability to transmit light.

Sound Test for Hardness

Pottery produces a dull "thud" when tapped. Since it is less vitrified, its structure is softer and absorbs sound.

Porcelain emits a sharp "ping" sound. Its dense, glassy body resonates with a higher-pitched tone, indicating greater hardness.

These sensory differences—touch, sight, and sound—clearly distinguish pottery from porcelain in terms of texture and feel.

For example, the rough texture and earthy tones of pottery resemble bricks used in fireplaces, evoking warmth and a rustic charm.

Pottery’s texture is slightly uneven, and if examined closely, its surface may show minute fibers or raised grain from the clay composition. Running your fingers over it with closed eyes accentuates its rugged, tactile quality.

In contrast, porcelain’s smooth, polished surface feels like the white tiles found in bathrooms. Its even, glossy texture and crisp white color give a cool, refined appearance.

Examining a freshly trimmed porcelain surface reveals a seamless, polished look, almost resembling sculpted marble. The contrast between the roughness of pottery and the precision of porcelain highlights their fundamental textural differences.

Hardness is an indicator of a material’s actual strength. When tapped with a fingernail, pottery produces a dull "thud" due to its lower degree of vitrification. Because pottery is not as dense as porcelain, it is more prone to developing large cracks across the entire piece when it breaks.

In contrast, porcelain produces a high-pitched "ping" sound when tapped. Since it is more vitrified than pottery, it has a higher hardness and greater density. When porcelain breaks, it tends to shatter into fine cracks, similar to glass breaking.

These visual, auditory, and tactile differences contribute to the distinct texture and overall feel of pottery and porcelain.

5. Difference in Heat Conductivity

Pottery and porcelain differ in thermal conductivity, which determines how easily heat transfers through them. As previously mentioned, pottery has a porous structure.

Pottery contains numerous microscopic pores and gaps, both on the surface and within the clay body. These tiny spaces trap air, which acts as an insulator.

Because of this trapped air, pottery is less conductive to heat and has high heat retention. A good analogy is a down jacket, which takes time to warm up but retains heat well due to the air trapped inside.

Since pottery contains a significant amount of trapped air, its thermal conductivity is low, meaning heat transfers slowly.

In contrast, porcelain has a higher glass content, making it more conductive to heat and quick to cool down. Its dense, glass-like body has almost no air pockets, leaving little room for insulation. Because there is virtually no trapped air inside, heat transfers through porcelain much faster.

A simple comparison can be made using a frosted plastic cup and a transparent glass cup filled with hot water:

・Frosted plastic cup ≈ Pottery: Heat transfers slowly.

・Transparent glass cup ≈ Porcelain: Heat transfers quickly.

Plastic contains numerous microscopic air bubbles, which block heat transfer and make it appear frosted—similar to how pottery retains heat.

On the other hand, glass has almost no air bubbles, allowing both heat and light to pass through, much like porcelain.

When hot water is poured into these cups:

・The plastic (pottery) cup takes longer to heat up but retains warmth for an extended period.

・The glass (porcelain) cup heats up quickly but also cools down faster when exposed to air.

Thus, we can summarize their thermal properties as follows:

・Pottery: Warms up gradually and retains heat longer.

・Porcelain: Heats up quickly but also cools down faster.

These differences in heat transfer influence how pottery and porcelain are used in daily life.

6. Difference in Usage

As discussed, pottery and porcelain handle heat differently. This affects how they are used in various applications.

For example, consider matcha bowls and teacups. A pottery matcha bowl retains heat well, gradually warming up and staying warm. Raku ware (楽茶碗), Hagi ware (萩焼), and Karatsu ware (唐津焼) all fall into this category.

If hot matcha is poured into a pottery bowl, the heat transfers gradually, allowing the cup to remain comfortably warm in the hands. By the time the tea is finished, the bowl still retains some warmth.

Conversely, a porcelain matcha bowl conducts heat much faster. Holding it with hot liquid inside may feel too hot to the touch. For this reason, pottery is often preferred for hand-held cups containing hot liquids.

On the other hand, porcelain cups often feature handles, such as those on tea cups and coffee cups. Porcelain teacups, especially those made of white porcelain, enhance the color of coffee and tea while also being lightweight and easy to handle.

Another example is cooking ware, particularly earthenware pots (土鍋, donabe). Many traditional Japanese restaurants use ceramic pots for simmering dishes.

When cooking with a ceramic pot, the food is slowly heated over low heat. Once it reaches a boil, the heat can be turned off, but the residual heat stored in the ceramic continues to cook the food. This is a perfect example of how pottery’s heat-retention properties are used effectively.

Conversely, porcelain is often used for cold dishes, such as salad bowls. Because porcelain transfers heat quickly, it provides a pleasantly cool feeling when held, making it ideal for serving chilled foods.

Another example is cold noodle dipping cups (蕎麦ちょこ, soba choko). Porcelain versions not only look cool and refreshing but also feel pleasantly cold to the touch. Their thin-walled, lightweight construction makes them easy to handle.

These examples illustrate how the unique properties of pottery and porcelain influence their practical applications, leading to distinct uses that maximize their respective strengths.

7. Difference in Care & Handling

As discussed earlier, the differences between pottery and porcelain stem from their raw materials. These distinctions extend to how they should be handled and maintained in everyday use.

Even when considering tableware alone, pottery and porcelain require different care methods. Pottery is porous, meaning it absorbs water. The countless microscopic pores in its surface allow moisture to seep in, which also makes it more prone to absorbing stains from food and sauces.

In contrast, porcelain has a dense, non-porous structure, making it highly resistant to water absorption and staining.

Proper Handling of Pottery

Because pottery absorbs moisture, it is best to soak it in water before use. Pre-soaking fills the clay’s pores with water, preventing food particles and stains from seeping in.

For example, when using pottery dishes or serving plates, I personally soak them for 30 minutes to an hour before use. After soaking, I wipe the surface with a cloth before placing food on it. After use, I wash the dish immediately with mild detergent and warm water to help lift any oil residues.

Proper Handling of Porcelain

Porcelain, on the other hand, requires minimal preparation. Before use, a quick rinse with water is sufficient to remove any dust. Although porcelain has minimal water absorption, it is best to wash it soon after use to prevent long-term staining. However, porcelain does not require the same level of careful maintenance as pottery.

8. Summary of Differences