도자기 소성 시 유약의 종류와 선택 기준 Study on the Types of Ceramic Glazes and Selection Criteria during Firing

 

도자기 소성 시 유약의 종류와 선택 기준

1. 서론

도자기 제작에 있어 유약의 선택은 최종 제품의 외관과 기능성을 결정짓는 중요한 요소이다. 본 연구에서는 도자기 소성 시 사용되는 다양한 유약의 종류와 그 선택 기준에 대해 체계적으로 분석하고자 한다.

2. 유약의 정의와 기본 구성

유약은 도자기의 표면에 입혀지는 유리질 물질로, 제품의 미적 가치와 실용성을 향상시키는 역할을 한다. Rhodes(1973)에 따르면, 유약의 기본 구성은 다음과 같다:

1) 유리질 형성제: 주로 규석(SiO2)
2) 융제: 장석, 석회석 등
3) 안정제: 알루미나(Al2O3)
4) 착색제: 금속 산화물

3. 유약의 분류

3.1 소성 온도에 따른 분류

Kingery 등(1976)은 유약을 소성 온도에 따라 다음과 같이 분류하였다:

1) 저화도 유약: 800-1100°C
2) 중화도 유약: 1100-1200°C
3) 고화도 유약: 1200°C 이상

3.2 원료 처리에 따른 분류

Carty와 Senapati(1998)는 유약을 원료 처리 방법에 따라 다음과 같이 분류하였다:

1) 생유(Raw glaze): 원료를 그대로 사용하여 만든 유약
2) 프리트유(Fritted glaze): 원료를 미리 용융시켜 만든 유약
3) 휘발유(Salt glaze): 소성 과정에서 소금을 투입하여 만드는 유약

3.3 주원료의 특성에 따른 분류

Peterson(2002)은 유약을 주원료의 특성에 따라 다음과 같이 분류하였다:

1) 장석유(Feldspar glaze)
2) 석회유(Lime glaze)
3) 알칼리유(Alkali glaze)
4) 연유(Lead glaze)
5) 붕산유(Boric glaze)

3.4 외관 상태에 따른 분류

Richerson(2005)은 유약을 외관 상태에 따라 다음과 같이 분류하였다:

1) 투명유(Transparent glaze)
2) 유탁유(Opaque glaze)
3) 결정유(Crystalline glaze)
4) 매트유(Matt glaze)

4. 주요 유약의 특성과 선택 기준

4.1 장석유

장석유는 고온 소성용 유약으로, 주로 자기(porcelain)에 사용된다. Carter와 Norton(2007)에 따르면, 장석유의 특성과 선택 기준은 다음과 같다:

1) 특성:
   - 높은 내구성과 경도
   - 우수한 광택
   - 1200-1300°C의 고온에서 소성

2) 선택 기준:
   - 고온 소성이 가능한 경우
   - 높은 내구성이 요구되는 경우
   - 투명하고 광택 있는 표면이 필요한 경우

4.2 석회유

석회유는 중국 청자와 한국 고려청자에서 주로 사용된 유약이다. 한국도자재단의 자료에 따르면, 석회유의 특성과 선택 기준은 다음과 같다:

1) 특성:
   - 부드러운 질감과 은은한 광택
   - 1180-1280°C의 온도에서 소성
   - 환원 소성 시 청록색 발색

2) 선택 기준:
   - 중간 정도의 소성 온도가 적합한 경우
   - 부드러운 질감과 은은한 광택이 필요한 경우
   - 청자 스타일의 작품을 제작하는 경우

4.3 알칼리유

알칼리유는 가장 오래된 유약 중 하나로, 이집트의 파이언스 제품에서 처음 사용되었다. 국립중앙박물관의 자료에 따르면, 알칼리유의 특성과 선택 기준은 다음과 같다:

1) 특성:
   - 낮은 소성 온도 (800-1000°C)
   - 밝고 선명한 색상 표현
   - 표면 균열이 쉽게 발생

2) 선택 기준:
   - 저온 소성이 필요한 경우
   - 밝고 선명한 색상이 요구되는 경우
   - 장식용 도자기 제작 시

4.4 연유

연유는 납을 주요 융제로 사용하는 유약으로, 저온에서 소성이 가능하다. 그러나 납의 독성 때문에 현대에는 사용이 제한되고 있다. 특허청의 자료에 따르면, 연유의 특성과 선택 기준은 다음과 같다:

1) 특성:
   - 낮은 소성 온도 (750-1000°C)
   - 높은 광택과 선명한 색상
   - 유동성이 좋아 균일한 표면 형성

2) 선택 기준:
   - 저온 소성이 필요한 경우
   - 높은 광택과 선명한 색상이 요구되는 경우
   - 비식품용 장식품 제작 시 (독성 주의)

4.5 결정유

결정유는 소성 과정에서 의도적으로 결정을 생성시킨 유약이다. 서울대학교의 연구(2018)에 따르면, 결정유의 특성과 선택 기준은 다음과 같다:

1) 특성:
   - 독특한 결정 패턴 형성
   - 정교한 온도 조절이 필요
   - 주로 장식용 도자기에 사용

2) 선택 기준:
   - 독특한 시각적 효과가 필요한 경우
   - 정교한 온도 조절이 가능한 경우
   - 예술 작품 제작 시

5. 유약 선택 시 고려해야 할 추가 요인

5.1 소지와의 적합성

유약은 소지와 열팽창 계수가 유사해야 한다. 그렇지 않으면 균열이나 박리 현상이 발생할 수 있다. 한국세라믹기술원의 자료에 따르면, 소지와 유약의 열팽창 계수 차이는 10% 이내여야 한다.

5.2 사용 목적

도자기의 용도에 따라 적합한 유약을 선택해야 한다. 예를 들어, 식기용 도자기는 내구성과 내화학성이 높은 유약을 선택해야 한다.

5.3 소성 환경

가마의 종류와 소성 분위기(산화 또는 환원)에 따라 적합한 유약을 선택해야 한다. 예를 들어, 환원 소성 시 철 함유 유약은 청록색을 띠게 된다.

5.4 미적 요구사항

작품의 의도된 색상, 질감, 광택 등에 따라 유약을 선택해야 한다. 이는 작가의 예술적 의도와 밀접한 관련이 있다.

6. 결론

도자기 소성 시 유약의 선택은 과학적 지식과 예술적 감각이 조화를 이루어야 하는 복잡한 과정이다. 유약의 종류와 특성을 잘 이해하고, 소지와의 적합성, 사용 목적, 소성 환경, 미적 요구사항 등을 종합적으로 고려하여 적절한 유약을 선택해야 한다.

향후 환경 친화적이고 안전한 새로운 유약 개발에 대한 연구가 필요할 것으로 보인다. 특히 저온 소성이 가능하면서도 내구성이 높은 유약의 개발은 에너지 절약과 제품의 품질 향상 측면에서 중요한 과제가 될 것이다.

참고문헌

1. Rhodes, D. (1973). Clay and Glazes for the Potter. Chilton Book Company.

2. Kingery, W. D., Bowen, H. K., & Uhlmann, D. R. (1976). Introduction to Ceramics. John Wiley & Sons.

3. Carty, W. M., & Senapati, U. (1998). Porcelain—Raw Materials, Processing, Phase Evolution, and Mechanical Behavior. Journal of the American Ceramic Society, 81(1), 3-20.

4. Peterson, S. (2002). The Craft and Art of Clay: A Complete Potter's Handbook. Laurence King Publishing.

5. Richerson, D. W. (2005). Modern Ceramic Engineering: Properties, Processing, and Use in Design. CRC press.

6. Carter, C. B., & Norton, M. G. (2007). Ceramic Materials: Science and Engineering. Springer Science & Business Media.

7. 한국도자재단. (n.d.). 도자기 유약의 종류와 특성. Retrieved from https://www.kocef.org/

8. 국립중앙박물관. (n.d.). 한국 도자기의 유약. Retrieved from https://www.museum.go.kr/

9. 특허청. (n.d.). 도자기용 무연유약 개발 동향. Retrieved from https://www.kipo.go.kr/

10. 서울대학교. (2018). 결정유에 관한 연구. S-Space.

11. 한국세라믹기술원. (n.d.). 도자기 유약 기술. Retrieved from https://www.kicet.re.kr/

12. 국립문화재연구소. (2012). 전통 도자기 제작기술. Retrieved from https://www.nrich.go.kr/

Citations:
[1] https://www.garbotableware.com/ko/tableware-acticles/what-you-know-about-glaze-of-porcelain-tableware.html
[2] https://nowiknow.co.kr/entry/%EB%8F%84%EC%9E%90%EA%B8%B0-%EA%B3%B5%EC%98%88-%EC%9C%A0%EC%95%BD%EC%9D%98-%EC%A0%95%EC%9D%98%EC%99%80-%EC%9C%A0%EC%95%BD%EC%9D%98-%EC%A2%85%EB%A5%98
[3] https://m.cafe.daum.net/kangnamceramic/FmwB/6?listURI=%2Fkangnamceramic%2FFmwB

한국도자재단

 

국립중앙박물관

 

특허청

 

한국세라믹기술원

 

https://www.nrich.go.kr/

 

도자기 식기의 "유약"에 대해 알고 있는 것

 

 

유약의 개념

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Study on the Types of Ceramic Glazes and Selection Criteria during Firing

1. Introduction

In ceramic production, the choice of glaze is a critical factor in determining the final product's appearance and functionality. This study systematically analyzes the various types of glazes used in ceramic firing and the criteria for their selection.

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2. Definition and Basic Composition of Glazes

Glaze is a vitreous material applied to the surface of ceramics, enhancing their aesthetic value and utility. According to Rhodes (1973), the basic composition of glazes includes:

1. Glass Formers: Primarily silica (SiO₂).
2. Fluxes: Materials such as feldspar and limestone.
3. Stabilizers: Typically alumina (Al₂O₃).
4. Colorants: Metallic oxides.

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3. Classification of Glazes

3.1 Classification by Firing Temperature

Kingery et al. (1976) classified glazes based on firing temperature as follows:

1. Low-fire glazes: 800–1,100°C.
2. Mid-fire glazes: 1,100–1,200°C.
3. High-fire glazes: Above 1,200°C.

3.2 Classification by Raw Material Processing

Carty and Senapati (1998) categorized glazes based on the processing of raw materials:

1. Raw glazes: Made directly from untreated raw materials.
2. Fritted glazes: Produced by pre-melting raw materials.
3. Salt glazes: Created by adding salt during firing.

3.3 Classification by Main Components

Peterson (2002) classified glazes based on the characteristics of their main components:

1. Feldspar glazes.
2. Lime glazes.
3. Alkali glazes.
4. Lead glazes.
5. Boric glazes.

3.4 Classification by Appearance

Richerson (2005) classified glazes based on their visual properties:

1. Transparent glazes.
2. Opaque glazes.
3. Crystalline glazes.
4. Matte glazes.

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4. Characteristics of Major Glazes and Selection Criteria

4.1 Feldspar Glaze

Feldspar glaze is a high-temperature glaze primarily used for porcelain. According to Carter and Norton (2007), its characteristics and selection criteria are:

1. Characteristics:
   • High durability and hardness.
   • Excellent gloss.
   • Firing range: 1,200–1,300°C.
2. Selection Criteria:
   • Suitable for high-temperature firing.
   • Required for durable surfaces.
   • Ideal for achieving transparent and glossy finishes.

4.2 Lime Glaze

Lime glaze is prominently used in Chinese celadon and Korean Goryeo celadon. The Korea Ceramic Foundation outlines its characteristics and selection criteria as:

1. Characteristics:
   • Soft texture and subtle gloss.
   • Firing range: 1,180–1,280°C.
   • Greenish-blue color under reduction firing.
2. Selection Criteria:
   • Suitable for medium firing temperatures.
   • Desired for soft textures and subtle gloss.
   • Ideal for celadon-style ceramics.

4.3 Alkali Glaze

Alkali glaze, one of the oldest glaze types, was first used in Egyptian faience. According to the National Museum of Korea, its characteristics and selection criteria are:

1. Characteristics:
   • Low firing temperature (800–1,000°C).
   • Bright and vivid color expression.
   • Prone to surface cracking.
2. Selection Criteria:
   • Suitable for low-temperature firing.
   • Required for vibrant colors.
   • Ideal for decorative ceramics.

4.4 Lead Glaze

Lead glaze uses lead as the primary flux and allows for low-temperature firing. Due to its toxicity, its use is restricted in modern ceramics. According to the Korean Intellectual Property Office, its characteristics and selection criteria are:

1. Characteristics:
   • Low firing temperature (750–1,000°C).
   • High gloss and vibrant colors.
   • Smooth, uniform surfaces.
2. Selection Criteria:
   • Suitable for low-temperature firing.
   • Ideal for high gloss and vibrant colors.
   • Used only for non-food decorative items (due to toxicity concerns).

4.5 Crystalline Glaze

Crystalline glaze creates intentional crystal formations during firing. Seoul National University’s research (2018) identifies its characteristics and selection criteria as:

1. Characteristics:
   • Unique crystal patterns.
   • Requires precise temperature control.
   • Primarily for decorative ceramics.
2. Selection Criteria:
   • Suitable for unique visual effects.
   • Requires precise temperature control capabilities.
   • Ideal for artistic ceramic pieces.

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5. Additional Factors in Selecting Glazes

5.1 Compatibility with the Clay Body

The glaze must have a thermal expansion coefficient similar to the clay body. Otherwise, cracking or peeling may occur. According to the Korea Institute of Ceramic Engineering and Technology, the difference should be within 10%.

5.2 Intended Use

The glaze should align with the intended use of the ceramic item. For example, tableware requires durable and chemically resistant glazes.

5.3 Firing Environment

The type of kiln and firing atmosphere (oxidation or reduction) influence glaze selection. For instance, iron-based glazes turn greenish-blue under reduction firing.

5.4 Aesthetic Requirements

The intended colors, textures, and gloss levels of the finished product must be considered. This factor is closely tied to the artist’s vision.

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6. Conclusion

Selecting glazes for ceramic firing is a complex process that combines scientific knowledge with artistic sensibility. Understanding the types and characteristics of glazes and considering factors such as compatibility with the clay body, intended use, firing environment, and aesthetic goals are essential for optimal glaze selection.

Future research should focus on developing environmentally friendly and safe glazes, especially those capable of low-temperature firing with high durability. Such advancements could contribute to energy efficiency and improve product quality.

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References

1. Rhodes, D. (1973). Clay and Glazes for the Potter. Chilton Book Company.
2. Kingery, W. D., Bowen, H. K., & Uhlmann, D. R. (1976). Introduction to Ceramics. John Wiley & Sons.
3. Carty, W. M., & Senapati, U. (1998). Porcelain—Raw Materials, Processing, Phase Evolution, and Mechanical Behavior. Journal of the American Ceramic Society, 81(1), 3–20.
4. Peterson, S. (2002). The Craft and Art of Clay: A Complete Potter's Handbook. Laurence King Publishing.
5. Richerson, D. W. (2005). Modern Ceramic Engineering: Properties, Processing, and Use in Design. CRC Press.
6. Carter, C. B., & Norton, M. G. (2007). Ceramic Materials: Science and Engineering. Springer Science & Business Media.
7. Korea Ceramic Foundation. (n.d.). Types and Characteristics of Ceramic Glazes. Retrieved from Korea Ceramic Foundation
8. National Museum of Korea. (n.d.). Glazes in Korean Ceramics. Retrieved from National Museum of Korea
9. Korean Intellectual Property Office. (n.d.). Trends in Lead-Free Glaze Development. Retrieved from KIPO
10. Seoul National University. (2018). Research on Crystalline Glazes. S-Space.
11. Korea Institute of Ceramic Engineering and Technology. (n.d.). Ceramic Glaze Technology. Retrieved from KICET
12. National Research Institute of Cultural Heritage. (2012). Traditional Ceramic Production Techniques. Retrieved from NRICH

Citations:
[1] https://www.valuetimes.co.kr/new/?bmode=view&idx=13695245
[2] https://encykorea.aks.ac.kr/Article/E0041641
[3] https://www.kipo.go.kr/ceramic-techniques
[4] https://s-space.snu.ac.kr/handle/10371/141838