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Chalk

Chalk. Products. Table of Contents. Classroom Chalk Colored Chalk Pastels Bibliography. Classroom Chalk.

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Chalk

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  1. Chalk Products

  2. Table of Contents • Classroom Chalk • Colored Chalk • Pastels • Bibliography

  3. Classroom Chalk • Regular classroom chalk is formed when water is added to calcium carbonate (CaCO3) to form slurry, like clay. This slurry is put into and extruded from a die. It is cut into sticks and placed in the oven. It cures for 4 days at 85 degrees Celsius (188 F). Water + Calcium Carbonate Slurry + 4 Days in oven at 85 C Classroom Chalk

  4. Colored Chalk • Colored chalk is formed when dry pigments are mixed with dry calcium carbonate. Water is added and the same process as regular chalk takes place. Dry pigments + Calcium Carbonate + Water Slurry + 4 days in oven at 85 C Colored Chalk

  5. Pastels • Pastels are manufactured just like classroom chalk, but rather than using CaCO3, calcium sulfate (CaSO4) is used. Clay and oils are mixed in with the dry material and slurry has the consistency of toothpaste. Pastels are usually air-dried rather than baked. Calcium Sulfate + Clays and oils + Water Slurry + Pastels Air Dry

  6. Putty • Glazing putty is commonly formed by mixing whiting (calcium carbonate) and boiled linseed oil. Other types of putty, such as painters putty and putties used for fire stopping are formed differently, through and endothermic reaction. MOST COMMON Whiting & Boiled linseed oil

  7. Variations of Putty Sealing Putty Powder Lead &Tin Oxides Red &White Lead(Pb) Oxides Linseed Oil + Hardens Linseed oil absorbs O2 from the air, holding calcium carbonate or metallic oxides, causes the mixture to harden Used in polishing

  8. Bibliography • "Results for "chalk"." Answers.com. 2008. Answers Corporation. 3 Nov 2008 <http://www.answers.com/topic/chalk>. • Chalk… by S.C. Asher • Pastel Chalks by Bill Gracey • Putty by AMagill • "putty: Definition from Answers." Answers.com. 2008. Answers Corperation. 3 Jan 2009 <http://www.answers.com/topic/putty>.

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