Types of Plaster Finishes
After the application of plaster, finishing applied on the final coat of plaster following are some of finishes.
• Smooth Coat Finish:
• Sand Face Finish:
• Rough Cast Finish or Spatter Dash Finish:
• Peddle Dash or Day Dash Finish :
• Depeter Finish :
• Scrapped Finish :
• Textured Finish :
• Special Material Used in Plastering for Finishing Coat :
Smooth Coat Finish:
In this type of finish, the finishing coat is a smooth and leveled surface. The mortar used is made of cement and fine sand 1:3. Mortar is applied with the help of wooden float.
Sand Faced Finish:
Sand faced finish is applied in two coats. The first coat is applied in 1:4 cement sand mortar of 12 mm thickness.
It is provided wish zig-zing lines. After curing it for seven days, the second coat is applied in the thickness 8 mm.
The mortar for second coat is prepared from the cement sand mix ratio 1:1. The sand of uniform size is used. A sponge is used in a second coat when it is wet.
The surface of final coat is finished by rubbing clean and washed sand of uniform size by means of wooden float. This results in the surface having sand grains of equal and uniform density.
Rough Cast Finish or Spatter Dash Finish:
1:1:3 = Cement: Sand: Aggregate are used to prepare mortar for this type of finish. The coarse aggregate may vary from 3 mm to 12 mm in size.
The mortar is thrown on the prepared plaster surface then by means of a large trowel. The surface is then roughly finished using a wooden float.
This finish is water-proof, durable, and resistant to cracking and crazing. It is used for external rendering.
Peddle Dash or Day Dash Finish :
In this finish, clean pebbles of size from 10 to 20 mm size are dashed against the final coat of plaster.
The pebbles may be lightly pressed into the mortar with the help of wooden float. The final coat of plaster is having Cement: sand mix proportion of 1:3 and thickens 12 mm.
Depeter Finish :
In this type of final finish coat of plaster is applied to have thickness 12 mm, and when it is a wet condition, the pieces of gravel flint are pressed with hand on the surface.
Flints of different colors may be used to obtain beautiful patterns.
Scrapped Finish :
The final coat of plaster of 6 to 12 mm applied. Then it is allowed to be stiffened for a few hours. The surface is scrapped in a pattern for a depth 3 mm.
Steel straight edge old saw blades or such other tools may be used for scrapped. Such a scrapped surface is less liable to cracks.
Textured Finish :
This is used with sketch plastering ornamental patterns or textured surface are made on the final coat of stucco plastering by working with suitable tools.
Special Material Used in Plastering for Finishing Coat :
To meet with some specific requirements of finished surfaces such as durability better appearance, fireproofing, heat insulation, etc. special materials are added in mortar.
The following are the special materials to be used.
• Acoustic Plaster :
• Asbestos marble Plaster :
• Barium Plaster :
• Granite Silicone Plaster:
• Plaster of Paris of Gypsum Plaster:
• Keene’s Cement Plaster :
Acoustic Plaster :
The materials like gypsum mixtures are added in mortar for finishing coat such a coat undergoes a chemical reaction and produces gas bubbles and due to the bubbles tiny openings are formed in the coat and it appears like a honeycomb.
These honeycomb minute openings absorb sound. Such plaster is useful in interior walls of halls auditorium etc.
Asbestos Marble Plaster :
For a better appearance of finishing coat, mortar is made of cement asbestos and finely crushed marble and applied as finishing coat.
Barium Plaster :
To protect persons working in X-ray rooms from radioactivity, finishing coat is applied with mortar made of cement, sand, and barium soleplate.
Granite Silicon Plaster:
Granite and silicon are mixed with mortar. This finish is used for a superior type of construction. It is a quick setting and elastic in nature. This eliminates cracks.
Plaster of Paris of Gypsum Plaster:
Ground gypsum is heated at 160o to 170o C to obtain plaster of parish. Plaster of Paris hardens with 3 to 4 minutes of adding water.
Suitable retarders are added to increase setting time. Plater of a parish is generally used in combination with lime for ornamental work and reporting carks.
Gypsum plaster has fire resistance, light weight. It does not shrink while setting. It has a sound-insulating properly. It is very useful for ornamental work.
However, gypsum plaster is soluble in water.
Keene’s Cement Plaster :
Kenees’s cement is obtained by calcination of plaster of Paris with alum. This is very hard and sets in a few days taking a white glass-like polish. It is useful for decorative work.