Lesson Plan: Glaze Demonstration. The Lesson

Transcription

1 Lesson Plan: Glaze Demonstration PLO s : developing knowledge and use of processes and techniques for ceramics and sculpture: surface treatment processes (e.g., polishing, glazing, staining, painting) developing knowledge of image development and design strategies by applying assigned strategies to personal artworks Lesson Overview: Presenting a demonstration on the ingredients/make up up glazes for ceramics, the variety of temperatures and types as well as a lesson on application. Materials: -bisque ware such as fired slabs to demo glaze application on. -Bamboo brush or any other type of soft hairde Goals: To have students learn the process of applying glaze to bisque ware. The Lesson Introducion: STATING OBJECTIVE (Why, What, How, When?): Why? To learn how to PROPERLY apply glaze to bisque ware What? What is glaze? Explain the contents and make up of glaze. How? With bisque piece, show how to properly apply glaze. 3 even coats with a soft brush is a MUST! When? Explain that you only apply glaze to bisque ware, NEVER to green ware. Explain WHY. Key Points: STATING INFORMATION (Important things to remember): -Explain why 3 coats are mandatory ie: even colors, even flux, no streaks, strength -Explain the ingredients of clay and what a flux is -Explain how to properly apply -Explain why only to apply it to bisque ware Demonstration: STEPS FOR A SUCCESSFUL DEMO: See next steps for tutorial on how to proceed with demonstration.

2 Teacher is...: Prompts that will engage students to perform a task: 1) Before class beings, ensure that the teacher has the demo table set up. Be sure to have: -Glaze -Soft brush such as bamboo brushes -W0rksheets or rescources (optional) -Bisque Ware to show how to glaze on. Pre-prepared bisque slabs would work best to show one, two and three coat strokes. -Water incase glaze is too thick 2)Prompt students to gather around table. Demo should be min MAX! Do at beginning of class. 3) a) Explain what a glaze is and the ingredients. Explain flux and how the color theory doesn t apply with glazes as they are created through chemicals, not colorants. b) Explain why it only goes on bisque ware c) Explain why to use a soft brush (no brush strokes, all even. Let glaze drizzle off brush) d) Explain why to match glaze temperature with clay termperature. e) Explain importance of three coat application of glaze. (Even flux, strength, thick, etc.) Explain how too much glaze will create runs or craters. f) Explain how glaze changes texture and color through firing. The color you put on won t be the color your glaze will be. Things change with heat! Chemical reactions! g)explain that GLAZE IS PERNAMENT! ONCE ITS ON THAT S IT! 4) Begin applying brush strokes. Apply one coat to one area, another area with two coats, last area with 3 coats. After it s fired they can see the difference. 5) Once having finished applying glaze, take questions. 6) After there aren t anymore questions, use a gage of understanding (assesment) technique: Using your hands, show me how much you knew about glazing your work (small space between hands means little knowledge, big space for a lot of knowledge) Students are...: What students will be doing after I do a task or prompt: 1) Students are entering classroom, setting into routine of the class. 2) Students move to round the demonstration table. 3) Students take notes or listen. They can think of questions or ask questions. Note: If they are not quite understanding the material or concept (anxiety or stress over glazing their work, provide them with a handout that has more information and glazing techniques) 4) Students watch closely as teacher performs demonstration as these steps are the most significant. 5) Students have the option of asking questions. 6) Students assess their own understandings of clay, silently, in response to the teacher s prompt. then... Using your hands, show me how much you know about glaze now

3 Closure: STUDENTS COMPLETING ACTIVITY (Share experience, critique, share work, etc): Teacher tells students to continue their projects they are working on. Teacher then proceeds to clean up the demonstration table then moves on to individual tutorials or meetings depending on what is on the agenda. Teacher Questions: QUESTIONS TO ASK DURING WORK TIME/END OF LESSON: -What kind of texture can glaze take on? -Are all glazes glossy? Or can they be matte, satin, or even something you ve never seen? (such as bead glaze) -Do all glazes work on all temperatures of clay? -Can you use the same glaze you would on work in an electric kiln as those for a fire pit for raku works? -What do you know about glazes? -What makes color in glazes? -What are the three main components in a glaze? Relfections: Your thoughts after lesson. How did it go?: Notes:

4 Ceramic Glazes - Info. for teacher use only - Page 1 Background The use of glazes is familiar in many everyday articles, however, the technology involved in composition and application is complex and diverse. Many, almost an infinite, number of variations are possible within many generic types e.g. clear, glossy, matt, coloured, textured. Glaze Systems Glazes are usually mostly comprised of a glassy material. In the case of opaque and matt glazes the glassy matrix contains crystalline matter. Certain glazes which contain large amounts of crystalline matter, deliberately grown in-situ to develop special properties, are described as glass-ceramic glazes. Opacity is occasionally produced by a phenomenon described as glass in glass phase separation. Glaze Components Although several glass-forming systems exist, ceramic glazes are almost exclusively based on alumino-silicate glass systems. The main glass forming oxide, silica (SiO2) is modified by the addition of a range of other oxides. The modifiers act to alter thermal, chemical, and physical properties, (table 1). Raw and Fritted Glazes Glazes are (regardless of colour, process/product type, and final surface texture) described as raw or fritted. Raw glazes are combinations of natural and synthetic materials such as feldspars, clays, quartz, carbonates and oxides of suitable composition to produce the final glaze. Fritted glazes contain a proportion of pre-melted glass or frit used when firing or compositional demands dictate the raw glazes cannot be made. Glaze Application The glaze materials are usually applied as a water-based suspension by spraying or dipping methods. Mechanisation is common though many craft and manual techniques persist. In some cases, dry and electrostatic methods are used. Glazes are applied to many varied substrates including table and giftware, sanitaryware, tiles, electrical porcelain, engineering ceramics and refractories. They are also applied to unusual substrates such as cement and graphite. Firing of Ceramic Glazes Conventional glazes are not fired below 950 C and may be fired as high as 1430 C depending on the application in question. In most cases, oxidising conditions are used but for certain products reducing conditions are required. Key Properties There are no fixed properties for glazes as their composition and use is so varied. The application of glaze may be purely for aesthetic reasons, functional purposes or both. One of the most common functional reasons is to provide an impermeable barrier to an otherwise porous ceramic body, as is the case with the common tea or coffee cup, while at the same time providing a visually pleasing surface to the article.

5 Ceramic Glazes - Info. for teacher use only - Page 2 The following properties are considered of importance, depending on the application and product/process types. Thermal expansion Glazes are normally required to be in compression in the fired state to avoid the fault of crazing, a differential of between 0.02% and 0.04% at around 550oC is normally recommended. Excessive compression can lead to the fault known as peeling. Colour The colours available will depend upon the firing temperature, the chemistry of the base glaze, and the composition of the chosen colour. Durability Depending on the application, chemical and physical durability may be of importance. Various tests are employed for the different product types to assess durability. Maturing Range Glazes must mature within an appropriate temperature and time interval. There must also be a suitable range over which maturity is reached in order to allow for process variables. This dictates the choice of glaze and the materials used to produce the glaze batch for a particular product. Applications Glazes are used in may applications. Some of these include: Sanitaryware toilets, basins, bath tubs etc Tableware dinner plates, crockery, ceramic cups and mugs etc. Tiles wall and floor tiles Ornaments giftware, figurines etc Electrical porcelains Refractories