Mineral: Gypsum, Calcium sulphateNotesCaSO4 2H2O is the crystalline mineral from which plaster is made. It is not practical as a source of CaO in glazes because its decomposition produces SO3 which is dangerous to health and it is destructive to the integrity of the glaze layer (and potentially the fired glaze quality).
Calcium sulphate has three different decomposition stages that generate water vapor and/or sulfur gases, two of which are reversible. These start below the boiling point of water and end well before 500C. Many ceramic clays, for example, contain sulfur, but either the percentage of slufur in the material is low or the percentage of the material used in glazes is low. Thus, in theory, calcium sulfate should be not responsible for glaze imperfections like blisters and pinholes (unless the glaze has a low melt fluidity or is fired very fast).
Calcium sulphate is often found in raw clay deposits as a partially soluble impurity that causes efflorescence, a plague to many ceramic industries (especially brick). During drying the salts are left behind of the surface of the clay to discolor it after firing. Barium carbonate is often used to precipitate this material.
Calcium sulphate reacts with sodium silicate and soda ash in a calcium-for-sodium ion exchange, and this process will eventually clog the pore structure of a mold used for casting slips containing it (the use of polyacrylate deflocculants will prevent this). Out Bound Links
In Bound Links
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The future of ceramic recipe, material and physical testing record keeping is here.
Maintain your recipe database on-line
- Login to a private account or work with others in a group account (e.g. university).
- Nothing to install (access it using your web browser). It is always the latest version.
- Easy to import your existing data.
- As many side-by-side recipes as you want.
- Many ways to search and classify glaze and body recipes.
- Glaze and body recipes are robust, with units-of-measure, unlimited pictures with individual titles and descriptions.
- Add variations to a recipe; each with its own pictures, descriptions and name/code-number extensions.
- Recipes can link to typecodes, projects and firing schedules (all managed in their own areas).
- Standard reports and mix ticket reports with last-minute-totalling; variations report as if they are a complete recipe.
- Video tutorials, help system, contact form on every page, dedicated messaging and support ticket systems.
- It is an industrial-strength database system (unlimited capacity, fast, reliable, scalable).
Imports many file formats
- Glaze recipe formats supported: HyperGlaze, GlazeGhem, GlazeMaster, Matrix, INSIGHT XML recipes (single and multiple), INSIGHT SQLite DB files.
- Assign a batch number to imports, and later search by batch.
- Assign multiple typecodes to imported glaze and body batches (to classify) and search on these later.
- Prepend character sequences to glaze recipe names during import.
- Import the pictures and pair them to their corresponding records automatically.
- One click to automatically export the database to an SQLite DB database file and download it (for use with desktop INSIGHT or just as a backup).
- Export and import individual glaze recipes as text or XML.
Perfect for Education
- Ceramic study programs can now accumulate material, recipe and testing data year-after-year, students can login and together build a valuable ceramic glaze and body knowledge resource.
- Students already have internet connected devices, computers are not even needed in the class.
- The Reference Manager gives you quick access to the Digitalfire Ceramic Reference Database.
Learn more..
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Watch the video or sign-up at http://insight-live.com.