Specification

Description
USG
™
accelerators are additives that shorten the setting time of gypsum plaster and setting-type joint
compound by causing gypsum crystals to form at a much faster rate. USG standard-strength gypsum plaster
accelerator is intended to provide a slight adjustment (10 to 30 minutes) to the setting time for veneer and
conventional plasters.
USG accelerator–alum catalyst corrects plaster dry-out conditions. It may also be used to treat sun-faded
ImperIal gypsum base when a lime-containing plaster is to be applied.
Directions USG Standard-Strength Four ounces (4 oz.) reduces the set time by 30 minutes per bag of veneer plaster product. Sprinkle dry
Gypsum Plaster
accelerator into the mixer after plaster has been added. For hand-mixing, dry accelerator can be added either
Accelerator
to the dry mix or the plaster slurry. Do not add accelerator directly to the water or mix with water before adding
to the plaster mix. When used in this manner, its ability to accelerate is significantly reduced. Sprinkle dry
accelerator into the mixer after plaster has been added. For hand-mixing, dry accelerator can be added either
to the dry mix or the plaster slurry.
USG Accelerator— To Correct “Dry-out” Conditions. Dry-out conditions can be corrected by either of the following methods:
Alum Catalyst
(1) Fog-spraying the plaster with water: Spray with a garden hose until beads of moisture remain on the
surface and the plaster is totally saturated. (If dry-out shrinkage fissures have developed in the plaster,
fill them by floating the surface with a wooden float after spraying.) (2) Spraying the damp plaster surface
with the prepared accelerator solution, using a hand-held pressure-type garden sprayer (3-5 gal. size).
Mix approximately 1/2 to 1 pound of powdered USG accelerator–alum catalyst to 3 gallons of water.
This solution is adequate to correct all surface dry-out conditions. The application of alum solution used in
combination with rewetting the affected areas will quicken the setting reaction and assist in preventing a
recurrence of the dry-out condition.
To Treat Sun-faded Gypsum Base. When used with lime-containing plaster, such as DIamonD
®
brand veneer finish,
sun-faded ImperIal gypsum base face paper should be treated with USG accelerator–alum catalyst or USG
™
plaster bonder. This precaution is unnecessary when applying products that do not contain lime (ImperIal
®
veneer
finish, ImperIal
®
basecoat and DIamonD
®
veneer basecoat).
Pour 3 pounds of alum-catalyst accelerator slowly into one gallon of water and mix thoroughly. Allow the
solution to stand until any undissolved material has settled, then strain the solution into a tank-type sprayer
(such as a garden sprayer). Spray the solution onto the faded ImperIal gypsum base face paper so that it is
wet but not soaked. One gallon of solution should treat 750 sq. ft. of ImperIal gypsum base. Begin finish plaster
application before face paper is completely dry. Caution: Alum treatment shortens the setting time of DIamonD
veneer finish.
Cleanup and Storage Clean mixing containers and tools with water immediately after use. Partially used containers should be
closed as tightly as possible. Store material in a cool, dry place. Avoid direct sunlight. Maintain temperature
above 40 °F (4 °C).
Submittal Sheet
09210
USG
™
Accelerators
For reducing the setting time of plasters and setting-type joint compounds
– Two formulations meet a variety of accelerated setting requirements.
– Products are safe and easy to use.
– USG
™
standard-strength gypsum plaster accelerator provides slight adjustments to set for veneer and
conventional plasters.
– USG
™
accelerator –alum catalyst corrects dry-out conditions and treats sun-faded ImperIal
®
brand gypsum base.