ABOUT GYPSUM BOARD USED IN CEILING & WALLS.

THE MINERAL GYPSUM

• Chemistry: CaSO4-2(H2O), Hydrated Calcium Sulfate
• Class: Sulfates
• Uses: plaster, wall board, some cements, fertilizer, paint filler, ornamental stone, etc..
• Specimens
• Gypsum is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.
• Gypsum has several variety names that are widely used in the mineral trade.
• "Selenite" is the colorless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the greek for Moon and means moon rock.
• Another variety is a compact fiberous aggregate called "satin spar" . This variety has a very satin like look that gives a play of light up and down the fiberous crystals.
• A fine grained massive material is called "alabaster" and is an ornamental stone used in fine carvings for centuries, even eons.                  
• Crystals of gypsum can be extremely colorless and transparent, making a strong contrast to the most common usage in drywall. The crystals can also be quite large. Gypsum is a natural insulator, feeling warm to the touch when compared to a more ordinary rock or quartz crystal. Sheets of clear crystals can be easily peeled from a a larger specimen.
• Gypsum crystals can be extremely large - among the largest on the entire planet. A cave in Naica, Mexico contains crystals that dwarf the people inside. Apparently, ideal conditions for the slow growth of gypsum were maintained for thousands of years, allowing a few crystals to grow to enormous sizes. Click on the photos for larger images, and see this abstract for an article in the April 2007 Geology magazine that describes how the growth of these gypsum megacrystals occurred.
• Plaster of Paris is made by heating gypsum to about 300 degrees Fahrenheit, driving 75% of the water out of the mineral.  This reaction absorbs energy, enabling a sheet of drywall to resist fire for a while. Heating further to about 350 degrees F drives out the remaining water and results in conversion to the mineral anhydrite.

   

Physical Characteristic

• Color is usually white, colorless or gray, but can also be shades of red, brown and yellow.
• Luster is vitreous to pearly especially on cleavage surfaces.
• Transparency crystals are transparent to translucent.
• Crystal System is monoclinic; 2/m
• Crystal Habits include the tabular, bladed or blocky crystals with a slanted parallelogram outline. The pinacoid faces dominate with jutting prism faces on the edges of the tabular crystals. Long thin crystals show bends and some specimens bend into spirals called "Ram's Horn Selenite" Two types of twinning are common and one produces a "spear head twin" or "swallowtail twin" while the other type produces a "fishtail twin". Also massive, crusty, granular, earthy and fiberous.
• Cleavage is good in one direction and distinct in two others..
• Fracture is uneven but rarely seen.
• Hardness is 2 and can be scratched by a fingernail.
• Specific Gravity is approximately 2.3+ (light)
• Streak is white.
• Associated Minerals are halite, calcite, sulfur, pyrite, borax and many others.
• Other Characteristics: thin crystals are flexible but not elastic, meaning they can be bent but will not bend back on their own. Also some samples are fluorescent. Gypsum has a very low thermal conductivity (hence it's use in drywall as an insulating filler). A crystal of Gypsum will feel noticeably warmer than a like crystal of quartz.
• Notable Occurances include Naica, Mexico; Sicily; Utah and Colorado, USA; and many other locallities throughout the world.
• Best Field Indicators are crystal habit, flexible crystals, cleavage and hardness.

 How to fix Gypsum Boad for partation of Walls  or Ceiling:

 

• Gypsum board is often called drywall, wallboard, or plasterboard. It differs from other panel-type building products, such as plywood, hardboard, and fiberboard, because of its noncombustible core and paper facers. When joints and fastener heads are covered with a joint compound system, gypsum wall board creates a continuous surface suitable for most types of interior decoration.

• Advantages of Gypsum Board Construction:

  Gypsum board walls and ceilings have a number of outstanding advantages:
  ◦ Ease of installation
  ◦ Fire resistance
  ◦ Sound isolation
  ◦ Durability
  ◦ Economy
  ◦ Versatility

  Common Types of Gypsum Board in Alphabetical Order:

  • Abuse-resistant gypsum panels offer greater resistance to surface indentation, abrasion and penetration than standard gypsum panels.

  • Eased edge gypsum board, which has a tapered and slightly rounded or beveled factory edge. It may be used as an aid in custom finishing of joints.

  • Exterior gypsum soffit board is board designed for use on the undersides of eaves, canopies, carports, and other commercial and residential exterior applications with indirect exposure to the weather. Soffit board is available in 1/2 or 5/8 -inch thicknesses with both regular and Type X core.

  • Foil-backed gypsum board has aluminum foil laminated to the back surface of regular gypsum board or other gypsum panel products. Foil-backed panels serve as vapor barriers.

  • Gypsum base for veneer plaster serves as a base for thin coats of hard, high strength gypsum veneer plaster.

  • Gypsum liner board serves as a liner panel in shaft walls, stairwells, chase ways, area separation fire walls, and corridor ceilings. It has a special fire-resistant core encased in moisture-resistant paper. Liner board is available in ¾ or 1 -inch thicknesses, widths of 24 or 48 inches and with square edges (sometimes eased square edges). Gypsum liner board is also available with fiberglass mat facing that increases its weather and mold resistance.

  • Gypsum sheathing is used as a protective fire resistive membrane under exterior wall surfacing materials such as wood siding, masonry veneer, stucco and shingles. It also provides protection against the passage of water and wind and adds structural rigidity to the framing system. The noncombustible core is surfaced with water repellent paper; in addition, it may also have a water resistant core. Available in 2 feet and 4 feet widths, ½ -inch and 5/8 -inch thick. It is also available with Type X core. Gypsum sheathing is also available with a glass mat facing. This product is more weather resistant and mold resistant than paper-faced gypsum sheathing, and it is often used as a substrate for Exterior Insulating Finishing Systems (EIFS).

  • Impact-resistant gypsum panels offer greater resistance to the impact of solid objects from high traffic and vandalism than standard gypsum panels.

  • Mold-resistant board incorporates various methods of preventing the growth of mold and mildew on the board’s surface.

  • Non-paper-faced gypsum board is unfaced or has a facing other than paper.

  • Regular gypsum board (gypsum wallboard) is used as a surface layer on walls and ceilings.

  • Sag-resistant board is a ceiling panel that offers greater resistance to sagging than regular gypsum products used for ceilings where framing is typically spaced 24 inches o.c.

  • Type C or Proprietary Type-X gypsum board is available in ½ -inch and 5/8 -inch thicknesses and is required in some fire rated assemblies. Additional additives give this product improved fire resistive properties.

  • Type X gypsum board is available in ½ -inch and 5/8 -inch thicknesses and has an improved fire resistance made possible through the use of special core additives. It is also available with a predecorated finish. Type X gypsum board is used in most fire rated assemblies.

  • Water-resistant gypsum board has a water resistant gypsum core and a water repellent paper. It serves as a base for ceramic or plastic wall tile or plastic finish panels in non-wet areas. This product is available with a regular or Type X core and in ½ -inch and 5/8 -inch thicknesses.

  Note: Do not use water-resistant gypsum board on ceilings or soffits unless extra framing is installed; do not exceed 12 inches o.c. between framing members. Do not use water-resistant gypsum board as a tile-backing substrate material where the final surface is directly exposed to running water; select one of several specialty products, including glass-mat-faced gypsum board or cement-based board, as a tile-backing substrate for areas directly exposed to running water.

  
  

  Tools Gypsum board installation and finishing require only some basic tools. While there are also many specialized hand and power tools available for gypsum board installation, here’s a list with brief descriptions of the basic tools necessary for a typical wallboard job: Measuring tape – A steel retractable measuring tape, usually 25 feet in length. Gypsum board T-square –Square edge for measuring and cutting gypsum board to length and for cutting out holes for square outlet boxes and other openings. Utility knife – Standard cutting tool with replaceable/reversible blades for scoring and cutting gypsum board. Hammer – Drives nails through gypsum board into wood framing. Keyhole saw – Small triangular saw for cutting out holes for outlet boxes, pipes, and other penetrations. Rasp – A tool for smoothing rough edges of wallboard after it has been scored and snapped. Assorted trowels and taping knives – Bladed tools for applying and smoothing tape and joint compound over joints and fastener heads. Mud tray – Box to contain joint compound while finishing joints and fastener heads. Sanding pole – Tool that enables sanding walls from floor to ceiling and standard height ceilings without the use of a ladder. Screw gun – Power tool that drives all types of gypsum board screws through gypsum board and into framing or substrate.

  Application Sequence:

  Use the following procedures to ensure a successful gypsum board application:

  1. Install ceiling panels first, then the wall panels.

  2. Once cut to size, position gypsum boards into place without forcing them.

  3. Match similar edges and ends, i.e.: tapered to tapered, square-cut ends to square ends.

  4. Plan to span the entire length of ceilings or walls with single boards if possible to reduce the number of butt joints, which are more difficult to finish. Stagger butt joints and locate them as far from the center of the wall and ceiling as possible so they will be inconspicuous.

  5. In a single-ply application, position all board ends and edges over parallel framing members to ensure that the joints are supported. (Exception: In a two-ply assembly, with adhesive between the plies, the ends and edges of face layers need not fall on supporting members.

  Take care to install mechanical and electrical equipment at the proper distance relative to the framing to allow for the gypsum board thickness so that the trim components, such as cover plates, registers, and grilles, fit correctly. Do not allow the depth of electrical boxes to exceed the framing depth and avoid placing boxes on opposite sides of a wall in the same stud cavity space. Avoid having electrical boxes, cabinets, and other devices penetrate completely through walls as this can be detrimental to sound isolation and fire resistance