Health & Safety in Ceramics

Preparation, Application and Firing

Ceramics is one of the most rewarding and enjoyable of all hobbies, and one of the safest, if some simple commonsense precautions are taken. As with any activity, responsibility must be taken for safe practices.

General rules of good housekeeping and common sense should be applied when doing ceramics. Following simple rules will ensure your safety and help you produce great results when creating a ceramic project.

It is necessary to read health and safety information, and to talk to your dealer, distributor or certified ceramics technoligits about the safe use of ceramic products. MSDS (Material Safety Data Sheets) are available with your suppliers and it is essential to get them with the materials.

Materials should be properly labeled for material safety. Read labels with care. In ceramics, as in all areas of human activity, proper usage of products ensures safety. It is the responsibility of the user to read and understand the product label and to follow the guidelines for safety. Anyone not able to understand and follow the label instructions and safety guidelines should have a competent person supervising the application and usage of all ceramic products. Also the guidelines could translate, transform in to an unstandable format to the operative. The operations include the preparation, application and firing of these products. The person firing a kiln should have complete knowledge of and understand the specific instructions for operation of the kiln as provided by the manufacturer. The user should know any local ordinances applicable to the installation of the kiln.

To ensure your health and safety, follow these simple rules:

• Keep work surfaces and areas clean.
• Clean up spills when they occur. Do not allow to dry.
• Keep dust under control at all times.
• Do not smoke, eat or drink when working with hazardous ceramic materials. Do not put your brush or brush handle in your mouth.
• Wash your hands before you begin. The natural body oils and salts on your hands may affect the finished piece (in manual processing activities).
• Any open cuts should be properly covered.
• Wash your hands thoroughly when you are through working.
• Use a smock when working with ceramic materials. Wash often and separately from other garments.
• Keep children away from kilns and out of glaze dipping rooms. Only a qualified operatives should operate a kiln.
• Children should not use lead-containing glazes or other hazardous ceramic materials.
• Do not intermix dinnerware safe glazes containing lead.
• If pregnant or contemplating pregnancy, tell your physician about your work with ceramics.
• When using solvent-containing ceramic materials, work out doors, in a locally exhausting hood or with an exhaust fan. Do not use or store near kilns, other heat sources or an open flame. Dispose of used rags in an airtight metal container.
• Do not fire kilns in an enclosed area. Use a kiln ventilation system. Carbon monoxide fumes can build up and present a danger. Consult with your kiln supplier or manufacturer for more information.
• If you should ingest ceramic products, seek medical help immediately.

The labels on a product are very important and give you a wealth of information. Read the label for information on proper product use and hazards, if any.

Ceramic glazes are manufactured using a variety of raw materials. Most of the ingredients are mined and extracted from the ground. Some of these materials can be classified as toxic and if misused can be harmful. The key to safe use of all art materials starts with professional education and training.

Non-Toxic Glazes

Non-Toxic glazes are formulated without the addition of lead. They are tested for safety by an independent toxicologist. They meet FDA standards. You can use these glazes and products with confidence and ease. These products contain no materials in sufficient quantities to be toxic or injurious to humans or to cause acute or chronic health problems. This does not mean that any less care should be given while handling these products.

Dinnerware Safe (Food-Safe) Glazes

Many glazes are formulated to be safely used on surfaces that come into contact with food or drink.

• If surfaces will come into contact with food or drink, use only glazes that are labeled food or dinnerware safe. Follow label instructions closely.
• Do not mix lead-containing dinnerware safe glazes, as the balance of ingredients in each glaze will be disrupted. Each mixture would have to be re-tested by an approved laboratory to determine if the mixture is also food safe.
• It is the responsibility of anyone making pieces for resale to have them tested by an approved laboratory for lead release.
• Proper firing of dinnerware safe glazes is critical. Use shelf cones on the kiln shelves to ensure that the pieces are fired hot enough, even if the kiln is electronically controlled or has an automatic kiln sitter. Always fire in accordance with manufacturer’s instructions. If crazed or under fired, these glazes may not be food safe. Too heavy an application of glaze, fast firing or not firing to the proper shelf cone listed on the label may result in a glaze that does not meet the FDA standards.

Lead and/or Cadmium Containing Glazes

Lead and cadmium are used in many ceramic glazes. Cadmium is used to produce brilliant reds and yellows. Lead gives brilliance to the glaze and allows the glazes to mature well at lower firing temperatures (shelf cone 06). 

• Glazes containing lead and/or cadmium should be handled with respect.
• The dust from such glazes should not be inhaled. Anyone who is pregnant or contemplating pregnancy should only use these glazes with professional supervision. Use good personal hygiene when working with these types of glazes.

Sprays, Solvents and Overglazes

These products are easy to use safely and will present no problems as long as these important rules are observed:

• Containers should be kept tightly closed when not in use.
• Aerosol sprays, solvents and solvent-based overglazes should be used outdoors, with a locally exhausting hood or spray booth or a window exhaust to assure adequate ventilation.
• Do not use near an open flame or heat source.
• Clean up after use and dispose of products properly in a metal container designed for disposal of flammable materials. Contaminated materials can be washed or placed under water until final disposal.

Slip

The mixture of any fine powder like slip requires the use of a safety mask approved by OSHA. The work area should be well ventilated with a system that draws all dust. This area should be away from other working areas so as not to spread the fine dust particles. Good housecleaning habits are necessary when mixing and pouring slips. Wipe up spills immediately. Do not sweep the area. Chronic lung damage may result from prolonged inhalation and exposure to the clay dust.

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Characteristics Required for different applications of tiles

Characteristics	Floors		Walls		Test
Dimensions and surface quality	Interior	Exterior	Interior	Exterior	Reference
Length and width	X	X	X	X	ISO 10545-2
Thickness	X	X	X	X	ISO 10545-2
Straightness of sides	X	X	X	X	ISO 10545-2
Rectangularity	X	X	X	X	ISO 10545-2
Surface flatness (curvature and warpage)	X	X	X	X	ISO 10545-2
Surface quality	X	X	X	X	ISO 10545-2

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Classification of ceramic tiles with respect to water absorption and shaping

Ceramic tiles are classified in to 3 major groups and sub groups of them as per the water absorption and the manufacturing method.

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Technical Terms - Ceramic Tiles Manufacturing

These are the definitions given in ISO 13006 for ceramic tiles. 

Ceramic tiles

thin slabs made from clays and/or other inorganic raw materials, generally used as coverings for floors and walls, usually shaped by extruding (A) or pressing (B) at room temperature but may be formed by other processes (C), then dried and subsequently fired at temperatures sufficient to develop the required properties; tiles can be glazed (GL) or unglazed (UGL) and are incombustible and unaffected by light

Vitrified covering which is impermeable

Engobed surface

Clay-based covering with a matt finish which can be permeable or impermeable

NOTE          : A tile with an engobed surface is regarded as an unglazed tile.

Polished surface

Surface of an unglazed tile which has been given a glossy finish by mechanical polishing as the last stage of manufacture

Extruded tiles

[Designated as A]

Tiles whose body is shaped in the plastic state in an extruder, the column obtained being cut into tiles of pre- determined dimension

NOTE 1: This International Standard classifies extruded tiles as “precision” or “natural”. The classification is dependent upon the different technical characteristics as listed in the individual product standards.

NOTE 2: Traditional  terms  used  for  extruded  products  are  “split  tiles”  and  “quarry  tiles”  They   commonly indicate double-extruded and single-extruded tiles respectively. The term “quarry tiles” only refers to extruded tiles with a water absorption not exceeding 6 %.

Dry-pressed tiles

[Designated as B]

Tiles formed from a finely milled body mixture and shaped in moulds at high pressure

Tiles made by other processes

[Designated as C]

Tiles made by other than the normal commercial processes, i.e. extruded or dry-pressed

NOTE          : These tiles are not covered in this International Standard.

Spacer lugs

projections which are located along certain edges of tiles so that when two tiles are placed together, in line, the lugs on adjacent edges separate the tiles by a distance not less than the specified width of the joint

NOTE 1: Lugs are positioned so that the joint between the tiles may be filled with grout without the lugs remaining exposed. NOTE 2 Dry-pressed tiles may be made with other spacer lug systems and, in such cases, the manufacturer’s work size applies.

Water absorption

[Symbol E]

Percentage of water by mass, measured in accordance with ISO 10454-3

Description of sizes

NOTE          : These are only defined for rectangular tiles. If the sizes of non-rectangular tiles are required, they are defined by the smallest rectangle into which they will fit.

Nominal size

Size used to describe the product

Work size [symbol W]

Size of a tile specified for manufacturing to which the actual size has to conform within specified permissible deviations

NOTE: This is specified by the dimensions length, width and thickness.

Actual size

Size obtained by measuring the face of the tile in accordance with ISO 10545-2

Coordinating size [symbol C]

Work size plus the joint width

Modular size

tiles and sizes based on module M, 2 M, 3 M and 5 M and also their multiples or subdivisions, except for tiles with a surface area of less than 9 000 mm2

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ISO Test Methods for Ceramic Tiles Testing

The below test methods are used for checking physical and chemical properties of Ceramic tiles.

1. ISO 1006:1983, Building construction — Modular coordination — Basic module.
2. ISO 10545-1:1995, Ceramic tiles — Part 1: Sampling and basis for acceptance.
3. ISO 10545-2:1995, Ceramic tiles — Part 2: Determination of dimensions and surface quality.
4. ISO 10545-3:1995, Ceramic tiles — Part 3: Determination of water absorption, apparent porosity, apparent relative density and bulk density.
5. ISO 10545-4:1994, Ceramic tiles — Part 4: Determination of modulus of rupture and breaking strength.
6. ISO 10545-5:1996, Ceramic tiles — Part 5: Determination of impact resistance by measurement of coefficient of restitution.
7. ISO 10545-6:1995, Ceramic tiles — Part 6: Determination of resistance to deep abrasion for unglazed tiles. ISO 10545-7:1996, Ceramic tiles — Part 7: Determination of resistance to surface abrasion for glazed tiles. ISO 10545-8:1994, Ceramic tiles — Part 8: Determination of linear thermal expansion.
8. ISO 10545-9:1994, Ceramic tiles — Part 9: Determination of resistance to thermal shock.
9. ISO 10545-10:1995, Ceramic tiles — Part 10: Determination of moisture expansion.
10. ISO 10545-11:1994, Ceramic tiles — Part 11: Determination of crazing resistance for glazed tiles.
11. ISO 10545-12:1995, Ceramic tiles — Part 12: Determination of frost resistance.
12. ISO 10545-13:1995, Ceramic tiles — Part 13: Determination of chemical resistance.
13. ISO 10545-14:1995, Ceramic tiles — Part 14: Determination of resistance to stains.
14. ISO 10545-15:1995, Ceramic tiles — Part 15: Determination of lead and cadmium given off by glazed tiles.
15. ISO 10545-16:—1 , Ceramic tiles — Part 16: Determination of small colour differences.
16. ISO 10545-17:—1), Ceramic tiles — Part 17: Determination of coefficient of friction.

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What is "Ceramic"?

A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass). Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the noncrystalline glasses, a distinction followed here.

The earliest ceramics made by humans were pottery objects, including 27,000 year old figurines, made from clay, either by itself or mixed with other materials, hardened in fire. Later ceramics were glazed and fired to create a colored, smooth surface. Ceramics now include domestic, industrial and building products and a wide range of ceramic art. In the 20th century, new ceramic materials were developed for use in advanced ceramic engineering; for example, in semiconductors.

The word "ceramic" comes from the Greek word κεραμικός (keramikos), "of pottery" or "for pottery", from κέραμος (keramos), "potter's clay, tile, pottery". The earliest mention of the root "ceram-" is the Mycenaean Greek ke-ra-me-we, "workers of ceramics", written in Linear B syllabic script. "Ceramic" may be used as an adjective describing a material, product or process; or as a singular noun, or, more commonly, as a plural noun, "ceramics".

Adopted from Wikipedia

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