CHAPTER ONE INTRODUCTION
1.0 Background to the Study
The normal production processes involved in ceramic design and practice is often times tedious and demanding. The necessities for faster mode of production such as the use of plaster of Paris mould have become imperative for ceramic production process in recent times. The production and use of moulds in their various forms seem to bring relief and solution to initial production methods that seem more strenuous at accomplishing mass production. Although there are various types of moulds, the plaster of Paris mould appears to be the type common with most ceramic mass productions. Ceramic moulds are made from plaster of Paris produced from gypsum. It was first developed in Montmartre, France around 1770, which gave rise to its name plaster of Paris and the discovery revolutionised mass production by slip casting. Gypsum is a rock or natural mineral that is mined from the earth, usually referred to as hydrous calcium sulphate, or (CaSO₄.2H₂O). When gypsum is exposed to heat treatment, 75% of water loss is recorded. This changes it to hemihydrates (CaSO₄.½H₂O). In other words, gypsum + heat = plaster (and ¾ water which evaporates). The making of plaster is done by grinding gypsum, and then heating it until the chemically-bonded water partially evaporates from 1000C to about 180⁰C.
It is evident from past studies that gypsum is available in Nigeria. Researchers and writers alike have tried to establish this fact from their findings. Examples of such reports can be found with the Ministry of Solid minerals Development 2000, and Mohammed-Sani, 2002. According to Akpakip, (1993), moulds may come in various forms but the medium which can best be adapted for ceramic production is gypsum plaster. This is so because moulds made from plaster have the ability or tendency to absorb large quantity of water from casting slip,
thus making it a cheap and reliable medium for ceramic production that cannot for now, be substituted with other media. Generally, moulds may be produced using other media such as metal, cement, wood, earthenware, silicone gel, polyvinyl and so on, (Sullayman, 2006, Akomolafe, 1991). Moulds of different types are often used to execute both small and large projects. These could work well for non-clay processes and allied disciplines but not with ceramic mass production due to the peculiarity of its production. This may be due to the fact that most ceramic productions use clay in wet state (plastic or slurry) or such materials (ceramic bodies) that form or dry on plaster moulds. An exception is when other mechanical processes like dust / granular pressing, isostatic pressing, tape casting, and rain pressing, and so on are involved. However, the fact remains that whether mould is made in a single one piece, two-piece, three-piece or multiple-piece form, its production helps in replicating art, craft or other industrial products exactly, either in relief or in-the-round. In other words, to attain accuracy, uniformity in weight, size and finishing, mould-making and its usage are desirable. Akpakip, (1996) worked on using gypsum in the area of plaster of Paris production. The major thrust of this study is to analyse the composite nature of gypsum which can be used as guide toward producing ceramic plaster.
There are some undeniable facts about the importance of mould in ceramic production that should be addressed and discussed at this stage. The first is that moulds are good for precision and replication for the production either in general art/craft works (in the form of household utensils or decorative wares), or in the minute scientific ceramic productions such as dentures and other medical body part replacement. Secondly, availability of mould and its use reduces time spent on the job and conserves energy which can be directed toward production of more ceramic wares.
1.0 Background to the Study
The normal production processes involved in ceramic design and practice is often times tedious and demanding. The necessities for faster mode of production such as the use of plaster of Paris mould have become imperative for ceramic production process in recent times. The production and use of moulds in their various forms seem to bring relief and solution to initial production methods that seem more strenuous at accomplishing mass production. Although there are various types of moulds, the plaster of Paris mould appears to be the type common with most ceramic mass productions. Ceramic moulds are made from plaster of Paris produced from gypsum. It was first developed in Montmartre, France around 1770, which gave rise to its name plaster of Paris and the discovery revolutionised mass production by slip casting. Gypsum is a rock or natural mineral that is mined from the earth, usually referred to as hydrous calcium sulphate, or (CaSO₄.2H₂O). When gypsum is exposed to heat treatment, 75% of water loss is recorded. This changes it to hemihydrates (CaSO₄.½H₂O). In other words, gypsum + heat = plaster (and ¾ water which evaporates). The making of plaster is done by grinding gypsum, and then heating it until the chemically-bonded water partially evaporates from 1000C to about 180⁰C.
It is evident from past studies that gypsum is available in Nigeria. Researchers and writers alike have tried to establish this fact from their findings. Examples of such reports can be found with the Ministry of Solid minerals Development 2000, and Mohammed-Sani, 2002. According to Akpakip, (1993), moulds may come in various forms but the medium which can best be adapted for ceramic production is gypsum plaster. This is so because moulds made from plaster have the ability or tendency to absorb large quantity of water from casting slip,
thus making it a cheap and reliable medium for ceramic production that cannot for now, be substituted with other media. Generally, moulds may be produced using other media such as metal, cement, wood, earthenware, silicone gel, polyvinyl and so on, (Sullayman, 2006, Akomolafe, 1991). Moulds of different types are often used to execute both small and large projects. These could work well for non-clay processes and allied disciplines but not with ceramic mass production due to the peculiarity of its production. This may be due to the fact that most ceramic productions use clay in wet state (plastic or slurry) or such materials (ceramic bodies) that form or dry on plaster moulds. An exception is when other mechanical processes like dust / granular pressing, isostatic pressing, tape casting, and rain pressing, and so on are involved. However, the fact remains that whether mould is made in a single one piece, two-piece, three-piece or multiple-piece form, its production helps in replicating art, craft or other industrial products exactly, either in relief or in-the-round. In other words, to attain accuracy, uniformity in weight, size and finishing, mould-making and its usage are desirable. Akpakip, (1996) worked on using gypsum in the area of plaster of Paris production. The major thrust of this study is to analyse the composite nature of gypsum which can be used as guide toward producing ceramic plaster.
There are some undeniable facts about the importance of mould in ceramic production that should be addressed and discussed at this stage. The first is that moulds are good for precision and replication for the production either in general art/craft works (in the form of household utensils or decorative wares), or in the minute scientific ceramic productions such as dentures and other medical body part replacement. Secondly, availability of mould and its use reduces time spent on the job and conserves energy which can be directed toward production of more ceramic wares.
