Installation Guide

23
Condition
IN-PLACE CONDITIONS (cont.)
Bond Failure (cont.)
Hard (Set) Lumps In Package
Set Time Variable Within
The Same Job Mixed Batch
Set Time Variable From
Batch To Batch
Slow Set Plaster
Probable Cause
4. Excessive use of retarder to slow
setting, so partial dry-out occurs.
5. Adulteration of the plaster on the
job site by addition of substances
other than clean graded silica
sand or excessive use of sand.
6. Application of plaster over
improper substrate.
7. Application of plaster over
contaminated substrate, dust,
dirt, oil, soot, etc.
8. Application of plaster over
substrate with excessively high
suction – too high absorptivity.
9. Application of plaster over sub-
strate with inadequate absorp-
tivity – too low suction.
10. “Laying-on” or “buttering-on”
plaster without adequate trowel
pressure to provide mechanical
keying to the substrate.
11. Inadequate or insufficient fin-
ish troweling.
12. Basecoat plaster troweled too
smooth – reduces mechanical key-
ing of finish to the base plaster.
13. Finish plaster applied over base-
coat plaster too thick, and not tightly
troweled into the base plaster.
14. One coat finish applied too thin.
Plaster bags became wet
during transit or storage.
1. Improper mixing equipment.
2. Insufficient water used at the
start of mixing.
3. Insufficient mixing time.
1. Dirty equipment
2. No or improper equipment
clean-out procedures.
3. Partial bag mixed.
1. Temperature below 40°F (4°C)
or in excess of 100°F (38°C).
2. Job addition of retarder.
3. Use of old, improperly stored
plaster or plaster from open bags
which have been exposed to air.
4. Partial bag mixed.
Preventive Action
The best advice for preventing
veneer plaster problems is to strictly
follow the manufacturer’s recom-
mendations and adhere to
proper plastering practices.
Protect plaster from water
during transit and storage.
1. Use recommended mixing
equipment.
2. Add all but about 1 quart of the
recommended amount of water
to the mixer at start.
3. Mix to a uniform fluidity; mixing
time should not exceed 5 minutes.
1. Use only clean equipment.
2. Follow recommended equip-
ment clean-out procedures.
3. Use only full bags.
1. Avoid extremes of air, plaster
and mix water temperature.
2. Avoid job addition of retarder.
3. Use only properly stored plaster
from unopened bags, less than
a year old.
4. Use only full bags.
Corrective Action
Remove all loose or marginally
bonded plaster, brush the surface
thoroughly to remove dust
(vacuuming is recommended),
apply a quality bonding agent per
manufacturer’s recommendations
and replaster.
1. Screen out hard lumps before
mixing.
2. Discard the plaster.
See Prevention.
See Prevention.
1/2. During cold weather maintain
temperature between 55° and
70°F before, during and after
plastering. Avoid job additions of
retarder. Cautiously use accelera-
tor to speed up setting action.
3. Replace material.
4. Use only full bags.
PALSTER APPLICATION CONDITIONS