Because ceramic products and materials rarely just crack but usually fracture into many pieces, repairs are usually impossible or at best difficult, leaving the item compromised. Because many ceramic products are used in connection with food and water, the bonding agents must be considered relative to possible toxicity and integrity when exposed to temperatures and different foods. Providing all the broken ceramic item pieces or chips can be re-assembled, they can be best bonded together with a regular or fast setting 2 part clear epoxy cement which can be purchased at any hardware and most convenience stores.
- The epoxy cement will come in 2 tubes including the cement and the hardener. Mix adequate amounts from each tube of epoxy together on a separate surface like a piece of paper. Usually, a smaller nail or tooth pick will do this job.
- Using a small tool like the nail or tooth pick, apply modest amounts of the mixed epoxy to each broken surface and assemble the pieces, removing excess glue. The pieces may be held together with almost any kind of adhesive tape or held together using elastic bands until the epoxy has hardened. This can be a bit of a juggling act but it is quite important that the pieces be held as tightly together as possible. The repair can also be done in stages if there are several pieces.
Figurines – Non functional, decorative items like figurines can usually be economically bonded back together using this method dependent on the severity of the damage. If the figurine is of significant value, it will be worthwhile contacting a specialist who may be able to repair the item. Remember that these repairs can be very time consuming and expensive and will never restore the item to its original state.
Vases – Since all vases have a monolithic glazed surface at least inside, water tightness may not be insured using epoxy repairs. This may cause a repaired vase to sweat and may leave water stains on a wooden surface. Many ceramic pieces may be slightly porous, and water may wick into the broken surfaces of the ceramic which can cause expansion and further damage.
Most of us think of ceramic as those products used in our homes like dishes or mugs and perhaps our bathroom sinks or even in the bricks on the front of our houses. For the most part, ceramic or clay products are reasonably inexpensive and usually fragile or breakable. But, because ceramic materials have a wide range of properties, they have very extensive applications and uses. The word ceramic stems from the Greek word Keramos meaning inorganic, non-metallic materials whose utility is formed by the action of heat.
Many ceramic materials like kaolin is composed of some common and naturally occurring complex mineral compounds often including alumina or aluminum oxide (Al2O3) and sand (quartz) and are processed into powders. Some other more refined and different ceramic materials include oxides, nitrides and carbides in a range of particle sizes ranging from sub micron to sand-like sized particles. To achieve the desired and often very interesting properties, these materials are heated to different temperatures generally ranging from 1000 C (1600 F) to 1600 C (3000 F) and perhaps in different atmospheres like nitrogen. Some of those properties of ceramics are as follows:
- Very hard like aluminum oxide used in ballistic armor or bullet proof vests to very soft like terra cotta plant pots.
- Very tough (will not crack) like some aluminas or zirconia used in teeth implants and bone implants to very fragile like porcelain figurines and dinnerware.
- Light like bricks used in high temperature furnaces to very heavy like zirconia used to toughen industrial parts.
- Ceramic materials can be very good heat insulators like the alumina fiber used in the space shuttle tiles or very good heat conductors like the silicon carbide heating elements in some furnaces.
- Most porcelains used in electrical insulators are non conductors of electricity and some mixtures of some ceramic materials like yttrium and barium under certain conditions can be super conductors of electricity.
- Some ceramic materials like bricks used in normal construction are very inexpensive and some highly refined technical ceramics like borides and carbides used in industry are very expensive.
- Very corrosive resistant and chemically stable like the enamel coatings on some of our metal cooking pots and appliances.
Ceramics are all around us. It is interesting to know that ceramic materials play a very big part in our lives from very basic building materials and household products to very sophisticated materials used in our automobiles, cutting tools, scales, body implants, computers and hydrogen fuel cells just to mention a few. You may also find it very interesting to know that in the weaving industry, ceramic thread guides are used because they can resist the abrasion of thread constantly passing over a given point. Certain kinds of ceramic are so hard and light they are used to stop armor piercing bullets in personal body armor systems.
JBK uses ceramic to make Brown Sugar Savers because the fired ceramic material is very inert, safe and porous and will absorb a defined amount of water slowly releasing it over an extended period of time and softening the hard brown sugar. JBK also uses a special blend of ceramic materials to make Pot Minders or anti boil over kitchen gadgets used when cooking. The properties of the ceramic material attractive in this application include the material being inert, non porous and with a defined density to help prevent pots from boiling over when cooking on the stove. The JBK Bread Warmers work because the fired clay has a density and mass which is a slow conductor of heat and will hold the heat energy for some time when heated in the stove and this heat will keep bread or baking warm during a meal.
Generally, the ceramic powders are mixed with varying amounts of water and additives like binders so they become workable like plasticine and in this form, they are hand formed, pressed or extruded. This is the way most of our kitchen products are manufactured. The powders can also be mixed with larger amounts of water into a clay slurry and cast into molds which will remove some of the water and form a shape like a sink or toilet. The “green” or unfired products are then removed from the molds and cleaned, glazed and put into a furnace or kiln and often heat treated to very high temperatures sometimes in modified atmospheres. This is where the ceramic becomes very hard and the glaze melts to produce a protective and decorative glass finish on the products. Where very high tolerances are required like in ceramic pump parts, these parts are machined or polished with diamond abrasives after they are fired.
Ceramics can be found in places you might never expect. It is in products like watches (quartz tuning forks keeping time in watches), scales (piezoelectric ceramics which produce voltage when stress is applied to them) and automobiles (spark plugs, sensors and other engine parts). For example, most insulators used in major electrical transmission lines are made from glazed porcelains because they are electrical insulators, relatively inexpensive and are water resistant.
Some general groups of ceramic applications and disciplines include:
- utilitarian ceramics – dinner ware, hotel ware, sanitary ware, hotel ware
- structural ceramics – industrial equipment liners, chutes and pipes, rocket nose cones
- technical and advanced ceramics – armor, cars, fuel cells, filters, catalysts
- medical ceramics – dental and bone implants
- electrical substrate ceramics – insulators in computers and electronic equipment
- piezo ceramics – in scales
- refractory ceramics – as a heat insulator in furnaces or on the space shuttle
- construction ceramics – as bricks in a functional and decorative construction
- coating ceramics – enamel coating on appliances or wear resistant coatings in pipes
Archeologists have uncovered human-made ceramics that date back to at least 26,000 years. These ceramics were found in Czechoslovakia and were in the form of animal and human figurines, slabs, and balls and made of animal fat and bone ash and a fine clay material. After forming, the ceramics were heated to temperatures between 500-800°C in domed and horseshoe shaped kilns partially dug into the ground. While it is not clear what these ceramics were used for, it is not thought to have been a utilitarian one. The first use of functional pottery vessels is thought to be in 9,000 BC. These vessels were most likely used to hold and store grain and other foods and may have been liners for baskets.
It is thought that ancient glass manufacture is closely related to pottery making, which flourished in Upper Egypt about 8,000 BC. While firing pottery, the presence of calcium oxide (CaO) containing sand combined with soda and the overheating of the pottery kiln may have resulted in a colored glaze on the ceramic pot. Experts believe that it was not until 1,500 BC that glass was produced independently of ceramics and fashioned into separate items.
Since these ancient times, the technology and applications of ceramics (including glass) has dramatically increased. We often take for granted the major role that ceramics have played in the progress of humankind.