Plaster of Paris
Plaster of Paris (POP) is hemi hydrated form of Gypsum (CaSO4.2H2O) and makes hard Gypsum again when mixed with water. This gypsum is hard and adhesive in nature with heat & sound resistance and porous structure with high water absorption. It does not shrink or crack when dry which make it an excellent medium for ceramic casting molds. Due to the adhesive nature Plaster of Paris is used in various applications like wall coatings, ceilings on ceilings and cornices, etc. It is also used in medicine to make plaster casts to immobilize broken bones though some orthopedic casts. Formation of POP
CaSO4.2H2 O+Heat
140°C
= CaSO4. 1⁄2 (H2O)
| Physical properties | SiO2 | |
| Whiteness | 80-95 | Al2O3 |
| Consistancy | TiO2 | |
| Firing withstand temp | 120°C | Fe2O3 |
| Color | Pure White, White, Creamish White | MgO |
| Initial setting Time | CaO | |
| Ph (OF 10% Solution) | 6 to 8 | K2O |
| Residue (325#) Calibrated Sieve | < 2 % | Na2O |
| Wet To Dry Shrinkage | 3-4 | LOI |
| Final setting time | 30 to 45 min | |
| M.O.R (Kg/Cm2) | 45 – 60 | |
| B.D. | 0.5-0.6 gm/cc |
Types of POP:
- Ceramic Grade
- Construction Grade
- Medical Grade
Features
- Easy To Spread And Level
- Highly Fire Resistant.
- Thick Surface To Resist Normal Knocks After Drying.
- Expands Very Slightly On The Setting.
- Does Not Crack on Surfaces.
- Mixes Up Easily With Water.
- Gives A Decorative Interior Finish.
Applications
- Ceramic Molding
- Wall Ceilings
- Roof Ceilings
- POP Plate making
- Medical Use
- Article making, etc.
- Gives A Decorative Interior Finish.