ASE B2 Painting & Refinishing common mistakes
ASE B2 Painting & Refinishing · Understand the traps and how to avoid them.
Sanding a panel with a finer grit than the substrate or repair requires, then applying primer or sealer directly over sanding scratches or bare-metal areas without the proper scratch pattern or adhesion-promoting step.
Candidates conflate 'smoother is better' with 'correct surface profile' and skip the grit-progression logic (e.g., coarse to refine shape, then finer to remove the previous scratches, with the final grit matched to the product's recommended profile).
What to do instead
Memorize the scratch-pattern rule: each grit must fully remove the previous grit's scratches, and the final grit must match the coating manufacturer's recommended profile. Practice identifying which grit a given product data sheet calls for before topcoat.
Treating a bare-metal or plastic area as ready for primer/paint after only cleaning, without applying the correct conversion coating, etch, or adhesion promoter for that substrate.
Candidates lump all substrates together and forget that aluminum, steel, galvanized, and plastics each require different pretreatment to get adhesion and corrosion protection.
What to do instead
Build a substrate-to-pretreatment matrix (bare steel, aluminum, galvanized, plastic, existing finish) and drill it until the correct prep step for each is automatic.
Setting gun fluid and air settings by 'feel' or copying a number from memory instead of adjusting to the actual product viscosity, temperature, and the spray pattern observed on test paper.
Candidates memorize a single 'correct' pressure or needle setting and don't connect gun adjustment to the specific material being sprayed and ambient conditions.
What to do instead
Learn the adjust-in-order method (fluid, then fan, then air) and always verify with a test pattern. Understand how viscosity and temperature change atomization so you can reason rather than recall.
Cleaning a gun by soaking the entire gun or leaving solvent in the air passages, or reassembling with damaged/over-tightened seals and a misaligned air cap.
Candidates focus on 'get the paint out' and ignore that improper cleaning and reassembly cause the very defects (spitting, uneven pattern, leaks) the exam tests.
What to do instead
Follow the disassemble-clean-lubricate-reassemble sequence, keep solvent out of air passages, inspect the air cap and needle for damage, and use only compatible lubricant on moving seals.
Mixing by volume ratios incorrectly, such as inverting the ratio, ignoring the difference between volume and weight, or failing to account for reducer/hardener additions when computing total mix.
Candidates rush the arithmetic and don't distinguish mix ratios (e.g., 4:1:1) from simple percentages, and they forget that some products are specified by weight while others by volume.
What to do instead
Practice ratio problems with realistic numbers, write the ratio down before measuring, use graduated mixing cups correctly, and always add components in the specified order.
Choosing a color or variant by eye under poor or mismatched lighting and skipping a spray-out test card comparison against the vehicle.
Candidates trust a color chip or a code lookup alone and don't account for variant differences, fading, or the effect of booth lighting on metallic and pearlescent colors.
What to do instead
Always spray a test card, compare it to the panel under proper lighting from multiple angles (especially for metallics), and select the correct variant before mixing the full batch.
Spraying with the booth in the wrong mode or with filters/airflow compromised, or entering and spraying before the booth has stabilized airflow and the correct temperature.
Candidates treat the booth as a passive room rather than an engineered environment, and they don't connect airflow direction, filter condition, and balance to defect formation.
What to do instead
Know the booth's modes (prep, spray, cure, purge), the filter maintenance schedule, and the signs of airflow imbalance. Verify booth conditions before mixing or spraying.
Applying coats too wet, too dry, or with too little flash time between coats, and misjudging recoat windows.
Candidates chase 'full coverage' quickly and don't internalize how film build, flash time, and recoat window interact with temperature and product chemistry.
What to do instead
Learn to read the product data sheet for wet film build, flash time, and recoat window, and practice consistent pass speed and overlap so film build is controlled rather than guessed.
Confusing the cause of a defect, e.g., attributing runs to 'bad paint' rather than excessive film build or gun distance, or blaming solvent pop on the booth rather than on flash/recoat timing.
Candidates memorize defect names without linking each to its specific mechanism (application, environment, substrate, or material), so they pick a plausible but wrong cause.
What to do instead
Build a defect-cause-correction table organized by mechanism (too wet, too dry, contamination, wrong prep, wrong material) and drill cause-and-fix pairs rather than names alone.
Attempting to correct a defect (sanding out a run, buffing, or recoating) without first identifying and eliminating the root cause, and without confirming the finish has cured enough to correct.
Candidates jump to the visible fix and don't connect correction to the underlying cause, so the defect returns, or they sand/buff too early and create new defects.
What to do instead
Adopt the identify-cause-eliminate-then-correct sequence and know the cure/correction window for each product before sanding, buffing, or recoating.