Red Seal Painter and Decorator surface preparation practice questions.

Five free practice questions on surface preparation: block B of the Red Seal 404C Painter and Decorator exam, about 30 of its 130 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.

01The questions

1. Procedural · Primes surfaces

   A dried water stain on a plaster ceiling has bled through two coats of latex paint. The leak is fixed. How is the stain dealt with before repainting?

   1. Apply a third coat of the same latex paint.
   2. Prime it with a solvent-based stain blocker.
   3. Wash it with TSP, rinse it and repaint.
   4. Prime it with a waterborne drywall primer-sealer.
   Show the answer

   B. Correct. Water stains leave water-soluble deposits that re-dissolve in a water-based coat and bleed through it. A solvent-based (alkyd or shellac) stain-blocking primer does not re-wet them and seals them in; the ceiling is then repainted.

   Why not the others

   A. Each new coat of latex re-wets the stain and draws it through again. Seal it with a solvent-based stain blocker first.

   C. The stain is in the plaster, not on it, so washing does not stop it bleeding through the next coat. It needs a stain-blocking primer.

   D. An ordinary waterborne drywall primer is not a stain blocker: the stain re-dissolves in its water and bleeds through again.

   Source: Red Seal Occupational Standard, sub-task B-6.04

2. Recall · Treats metal surfaces

   Girders on a highway overpass, exposed to years of road salt, are blast cleaned to near-white and look clean, but a field test still finds chlorides on the steel. Why must these be removed before coating?

   1. They only stain the topcoat and do no harm.
   2. They react with epoxy to form amine blush.
   3. They make the blasted profile too shallow.
   4. They draw water in and blister the coating.
   Show the answer

   D. Correct. Soluble salts left on the steel pull moisture through the coating, causing osmotic blistering and underfilm corrosion. Blasting alone may not remove them, so they are removed and the steel retested to the specification's limit before coating.

   Why not the others

   A. Salts under a coating do serious harm: blistering and corrosion under the film, which is why specifications limit them.

   B. Amine blush forms on amine-cured epoxy when the curing agent reacts with carbon dioxide and moisture in the air, not from salts on the steel.

   C. Salts do not change the profile depth. Their harm is under the coating, where they attract water.

   Source: Red Seal Occupational Standard, sub-task B-9.01

3. Procedural · Repairs existing plaster surfaces and drywall

   Dozens of compound patches must be sanded on an occupied office floor where dust has to be kept to a minimum. Which tool suits the job?

   1. A sanding block with fine paper.
   2. A palm sander with a fine sheet.
   3. A pole sander with a sanding screen.
   4. A vacuum sander with a fine screen.
   Show the answer

   D. Correct. A vacuum sander draws the dust through its perforated screen or pad into a vacuum as it sands, keeping fine compound dust out of an occupied space.

   Why not the others

   A. Hand sanding with a block still releases fine dust into the room; nothing collects it.

   B. A palm sander without extraction throws fine compound dust into the air, and it can gouge soft compound.

   C. An ordinary pole sander lets the fine compound dust fall and drift through the room, which is what the occupied floor cannot have.

   Source: Red Seal Occupational Standard, sub-task B-10.01

4. Procedural · Repairs minor imperfections in wood

   The finishing nails in newly installed trim sit flush with the wood surface. The trim will be painted. What is done before the nail holes are filled?

   1. Spot-prime the nail heads and then caulk them.
   2. Set each head below the surface with a nail set.
   3. Fill over the flush heads and sand the filler smooth.
   4. Sink the heads with the face of the hammer.
   Show the answer

   B. Correct. A nail set drives each head a little below the surface without marking the wood, leaving a small hole that filler can fill to a sound depth. Filler skimmed over a flush head is too thin to hold, and the head soon shows through.

   Why not the others

   A. Caulk shrinks into a hole and cannot be sanded flush, so the dimples show through the paint. Set the heads and use a sandable wood filler.

   C. A film of filler over a flush head is too thin to stay; it cracks or pops off and the head shows, and can rust, through the paint. Set the heads first.

   D. Driving a head below the surface with the hammer face leaves a round hammer dent in the trim around every nail, which shows through paint. A nail set sinks the head without marking the wood.

   Source: Red Seal Occupational Standard, sub-task B-7.02

5. Recall · Chemically treats concrete and masonry surfaces

   Efflorescence was cleaned off a brick retaining wall and the wall was coated, but white deposits soon push through again. Why?

   1. The acid wash left the brick too rough to seal.
   2. Water still carries salts out of the masonry.
   3. The deposit is mildew that was not killed.
   4. The coating's pigment is reacting with the brick.
   Show the answer

   B. Correct. Efflorescence is the salt left behind when water carrying dissolved salts evaporates at the surface. Until the water source is stopped and the wall dries, salts keep arriving and push under or through the coating.

   Why not the others

   A. Etching roughens the surface for adhesion; it does not cause white deposits. The deposit returns because its source was never stopped.

   C. Mildew is a dark, growing stain. Efflorescence is a white, crystalline salt deposit left by evaporating water.

   D. Pigment does not react with brick to form a white bloom. The deposit is salt carried out of the masonry by water.

   Source: Red Seal Occupational Standard, sub-task B-8.02

02Answer key

03What block B covers

Getting the substrate ready: removing old coatings and wall coverings, cleaning, spot priming and sealing stains, sanding and caulking, treating and repairing wood, mechanical and chemical preparation of concrete and masonry, cleaning metal by abrasive blasting, power tools and hand tools to a named preparation grade, filling pits, and repairing plaster and drywall, with moisture checked before anything is primed.

The Red Seal Occupational Standard names this block “Prepares surfaces”. It carries 23.1% of the exam, about 30 of the 130 questions, split across five tasks. The share column is each task's weight within the block, as the standard publishes it.

04What the questions turn on

Water tells you what the slab will take

Water that beads on a degreased slab shows a sealer or curing compound that acid cannot etch, so the film is ground or blasted off first. A taped plastic sheet that collects moisture underneath shows vapour coming through the slab before any coating goes on.

Choose the primer for the problem

Water stains re-dissolve into a water-based coat and bleed through it, so they are sealed with a solvent-based stain-blocking primer. Sound glossy enamel takes a bonding primer after cleaning and scuff sanding.

Prime bare wood, then caulk

Primer seals thirsty wood so caulk bonds to a stable surface, and the finish coats then cover primer and caulk alike. Wood soft through most of its thickness is cut out and replaced, not filled.

Steel is cleaned to a named grade

Where blasting is not allowed, power tool cleaning to bare metal (SSPC-SP 11) removes all visible rust, mill scale and coating. Sharp edges are ground to a radius first, because a drying film pulls thin over a sharp edge and rusts there first.

05The other blocks

The 404C exam has six blocks. Each has its own page of free questions:

The 404C Painter and Decorator practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.