USG IMPERIAL Finish Plasters - Manual (Page 3)

Mixing Mix plaster with a cage-type paddle driven by a heavy-duty drill capable of producing 900-1000 rpm under no
load. The correct approximate water-plaster ratio for I
MPERIAL Brand Finish (hand application) is 11 to 13 qt./80 lb.
bag (10.5-12.0 L/36.3 kg. bag). Water usage for D IAMOND Brand Finish Plaster is approximately 12 to 15 qt. per
50-lb. bag.
Place the water in a 12- to 15-gal. smooth-sided container. Start the mixer, slowly add plaster and mix at least 2
minutes to disperse lumps completely. Do not mix more than 5 minutes. Overmixing shortens working time. Do not
mix more than can be applied in 30 minutes. Do not retemper.
For sand float finish with I MPERIAL Brand Finish Plaster, add up to 20 lb. (9 kg) of clean silica sand per 80-lb. bag to
achieve the desired texture. Using more than 20 lb. of sand per bag will diminish the plaster’s strength to less than
the optimum 3,000 psi. For an eye-catching texture, apply plaster in the normal manner but omit final troweling.
After surface has become firm, float to desired texture using a sponge, piece of carpet or other float. Use water
sparingly.
Note: If you add aggregate to D IAMOND Brand Interior Finish Plaster, you must add a suitable retarder to allow time
for proper application before the plaster sets. Add 1/4 to 1/2 teaspoon of USG™ Retarder for Lime Containing
Plasters per bag of aggregated D
IAMOND Brand Interior Finish Plaster to the mixing water to allow sufficient working
time. You can also use Cream of Tartar as an alternative retarder.
Plastering I MPERIAL and D IAMOND Brand Finish Plasters provide a wide range of finish options with distinct application systems:
1. One Coat, basecoat plaster is not used
2. Two Coat, finish coat over a base coat
3. Two Coat: D
IAMOND Brand basecoat and I MPERIAL Brand finish coat over D UROCK Brand Cement Board or F IBEROCK
Brand Abuse-Resistant Panels treated with a bonding agent
4. Two Coat: I MPERIAL Brand Finish Plaster—finish coat over sanded S TRUCTO -B ASE High-Strength Basecoat Plaster
One Coat System Scratch-in a tight, thin coat of Finish Plaster over the entire area, immediately doubling back with plaster from
same batch to full thickness of 1/16
Љ to 3/32Љ. Fill all voids and imperfections. Final-trowel after surface has
become firm, holding the trowel flat and using water sparingly. Do not over-trowel.
For texture finished surfaces, with or without the addition of job-added sand, omit final troweling. The surface is
textured naturally as the material firms and water is removed into the base.
You will obtain the best results by planning plastering to permit continuous application from angle to angle. Where
joining is unavoidable, use the trowel to terminate unset plaster in sharp clean edge—do not feather out. Bring
adjacent plaster up to terminated edge and leave level. Do not overlap. During finish troweling, use excess material
to fill and bridge joining.
Two Coat System I MPERIAL Brand Basecoat Plaster or D IAMOND Brand Veneer Basecoat applied to I MPERIAL Brand Gypsum Base, or
concrete block or monolithic concrete treated with USG Plaster Bonder. Leave the surface of the base coat rough
and open for the proper bond of finish coat. Allow the basecoat to set to provide proper suction for the finish coat.
Apply a finish coat of I
MPERIAL Brand Finish as indicated above.
Veneer Plaster Over Veneer Plasters provide increased resistance to abrasion, indentation and penetration when used over F IBEROCK ®
F IBEROCK ® Brand Abuse- Brand Abuse-Resistant Panels in commercial and institutional applications such as schools and retail locations.
Resistant Panels
In this two-coat veneer plaster system, D IAMOND Brand Veneer Basecoat Plaster and then I MPERIAL Brand Finish
Plaster are applied over F IBEROCK Brand Abuse-Resistant Panels attached to framing.
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