Installation Guide

24
Condition
Quick Set
Spreading Qualities
Vary Within Batch
Spreading Qualities Vary
From Batch To Batch
Smooth Or Texture Finish
Desired, Not Obtained
Blistering Of Smooth Finish
A common condition, especially
over “green” basecoat plaster,
less over gypsum veneer base
Fuzzing Or Ragging Of
Smooth Finish Surface
Probable Cause
1. Dirty equipment.
2. Excessive mixing.
3. Contaminated mixing water.
4. Plaster has become wet or
contaminated prior to mixing.
5. Excessive use of accelerator.
6. Excessively low air/plaster mix,
water temperatures below 40°F
(4°C).
7. Partial bag mixed.
1. Improper mixing equipment/
mixing action.
2. Insufficient water used at start
of mixing.
3. Insufficient mixing time.
4. Aggregate separation.
1. Inconsistent mixing.
2. Using part or open bags exposed
to air.
3. Old or improperly stored plaster.
4. Variable aggregate.
1. Surface of unset plaster being
worked at wrong time, too stiff
or too soft.
2. Suction of substrate too high or
too low.
3. Surface of plaster being worked
after plaster has set.
4. Intermixing material from different
manufacturers.
1. Application of water onto the
plaster surface with troweling
before sufficient stiffening
(“take-up”) has occurred.
2. Aggravated by cold plastering
surfaces.
1. Finish plaster surface lacks
sufficient water for adequate
trowel lubrication or slip during
“draw-up” operation.
2. Job-gauged finish components
not uniformly blended, causing
localized dry spots due to
uneven water retention.
3. Excessive trowel pressure, trowel
at wrong angle to the surface or
timing wrong for troweling.
Preventive Action
1. Follow recommended clean-out
procedures.
2. Do not exceed 5 minutes mixing
time.
3. Use only potable water.
4. Use only properly stored, uncon-
taminated plaster.
5. Maintain construction areas and
materials above 55˚F prior to,
during and after plastering.
6. Avoid job additions of accelerator.
7. Use only full bag.
Use recommended mixing equip-
ment, water ratio and procedure.
1. Follow recommended mixing
procedures.
2/3. Use only full, unopened bags,
which have been properly stored.
4. Replace aggregate and/or plaster.
1. Adjust finishing sequence to
meet plaster condition.
2. Gypsum Base: Adjust plaster
working time sequence to com-
pensate for high or low suction.
Basecoat Plaster: Apply finish
over “green” moderately dry
basecoat or dampen dry basecoat.
3. Follow recommended smooth or
texturing procedures.
4. Use only materials from single
producer to ensure compatibility.
1. Reduce trowel pressure during
“double-back” and “draw-up”
operation. Use water sparingly
and only after adequate plaster
“take-up” has developed or ini-
tial setting action has occurred.
2. Maintain recommended working
area temperature.
1. Wet trowel or sparingly apply
water on plaster surface during
“draw-up”. Avoid starting “draw-
up” too long after “take-up”.
2. Be sure job-gauged finish
components are uniformly and
thoroughly blended.
3. Decrease trowel angle to surface,
ease up on trowel pressure or
start troweling sequence sooner.
Corrective Action
1–5. Follow good recommended
plastering practices.
6. Cautiously use retarder to slow
set time.
7. Use only full bag.
See Prevention.
See Prevention.
See Prevention.
Eliminate blisters with strong
trowel pressure during final water
troweling operation, when plaster
is firm and/or setting action in
progress.
See Prevention.
PLASTER APPLICATION CONDITIONS (cont.)