Use and Care Guide

18
Conditions
CRACKING PROBLEMS (cont.)
Bond Failure
Discoloration/Banding
Dirt Collection
Variation in
Surface Textures
Joint Darkening
or Lightening
Joint Yellowing
TEXTURING PROBLEMS
Lumping
Mix Too Thin
Aggregate Fallout
(During Spraying)
Aggregate Floatout
Probable Cause
Improper heating and drying condi-
tions. Old stock. Excessive thinning
of compounds. Too little compound
under tape. Unbuffed joint tape.
Oily surfaces. Mixing with dirty or
excessively cold water. Compound
too dry before embedding tape.
Dirt collection may occur more
rapidly over nail or screw heads,
nailing members or over voids in
insulation due to a greater heat
loss and condensation.
Failure to sand properly, causing
scratching of compound and
scuffing of the wallboard paper.
No primer or poor quality primer.
Over-thinning of primer. Spray
application of primer.
Joints not dry when painted.
Painting under humid conditions.
Painting with low-grade latex and
paints. Suction variations of joint
compounds.
Slow drying. Fumes from partially
combusted gases. Painting over wet
joints and high alkaline material.
Too much water added to initial
mix. Adding water to powder.
Too much water added in initial
mix or inadequate soaking time in
cold water.
Spray gun too close to surface
and/or excessive air pressure at
nozzle.
Too much water added during ini-
tial mix and/or inadequate mixing
after initial water is added.
Preventive Action
Proper drying conditions. Mix in
clean container with clean tap water.
Rotate stocks. Avoid over-thinning
of compound and removing too
much compound from under tape.
Use Quick Set or ProForm
compounds and tape.
Two-layer laminated system.
Foil-backed gypsum board. Proper
insulation. Eliminate protrusion of
nails through wood furring on
exterior walls and ceiling.
Use finer grit sandpaper with care
to prevent raising nap of paper. Use
wet sanding method. Prime all sur-
faces with a quality drywall primer
as directed. Brush or roll primer.
Back roll after spray application.
Allow joints to thoroughly dry.
Avoid painting under extremely
high humidity conditions. Use
National Gypsum Joint Treatment
products. Prime entire surface with
quality drywall primer prior to
applying texture finish as finish
decoration. Apply two coats of
good quality latex paint.
Use permanent heat in cold
weather. Avoid painting over wet
joints. Avoid painting in high
humidity conditions.
Add powder to water using less
water than initially specified. After
mix is smooth and lump-free, add
remaining water to adjust mix to a
workable viscosity.
Use recommended water require-
ments in initial mix. Allow mixed
ingredients to soak for several
minutes, when necessary, if using
cold water.
Hold spray gun at proper distance
and angle from surface to
prevent aggregate fallout.
Use recommended water require-
ments and make sure water is
properly blended into mix.
Corrective Action
Remove all loose joint tape and
compounds by sanding or scraping
and repair as necessary.
Wash or repaint. Decrease dust
particles in the air by filtration in
forced air heating and exhaust
fans in kitchen.
When condition exists after paint-
ing, sand as necessary and prime
before finish coat of paint.
Allow thorough drying. Select test
area where condition is most
prevalent and repaint with good
quality sealing latex primer. If con-
dition persists, apply a good quality
primer/sealer, then repaint.
Apply a good quality primer/sealer,
then repaint.
Add powder until mix thickens.
Continue mixing until lumps
disappear.
Add powder until mix thickens.
Lower air pressure. Hold spray gun
at proper distance and angle from
surface to prevent excessive fallout.
Add powder until mix thickens.