ITI/NCVT Painter General (AITT Theory) common mistakes
ITI/NCVT Painter General (AITT Theory) · Understand the traps and how to avoid them.
When asked to convert a wet-film thickness (WFT) to dry-film thickness (DFT), candidates multiply by the volume-solids fraction instead of dividing by it, or they ignore volume solids entirely and give the same number for both.
The formula is remembered as a vague 'WFT and DFT are related by solids' without the direction of the operation. Trainees see 'volume solids 60%' and reach for 0.6 as a multiplier because multiplying feels natural. The concept that solvent leaves the film and therefore the dry film is thinner than the wet film is not internalised.
What to do instead
Anchor the logic physically: the wet film is thicker because it still contains solvent, so DFT must be the smaller number. Memorise DFT = WFT x volume solids (as a fraction) and WFT = DFT / volume solids, then always sanity-check that DFT < WFT. Practise five mixed problems (find DFT, find WFT, find volume solids) and state the direction of the inequality before calculating.
Candidates select the primer or coating system by colour or by trade habit ('we always use red oxide') rather than by substrate and service environment, so a alkyd primer is specified over galvanised steel or a zinc-rich primer is expected to perform under a decorative topcoat on a damp interior wall.
Workshop teaching often revolves around one familiar system, and colour is the most visible property. Selection criteria such as adhesion mechanism, saponification risk on zinc, or permeability are abstract and rarely practised as decision exercises.
What to do instead
Build a substrate-to-primer matrix (mild steel, galvanised, aluminium, concrete, plaster, wood) and a service-environment column (interior dry, exterior, immersed, chemical). For each cell state the primer type and the reason in one sentence (e.g. etch primer on galvanised for adhesion; alkali-resisting primer on new plaster to resist saponification). Rehearse by naming the reason before the product.
In defect diagnosis, candidates name the visible symptom as the cause, writing 'the paint peeled because it peeled' or listing 'poor adhesion' as the remedy, instead of tracing the fault to surface contamination, moisture, incompatible coats, or over-thick film.
Defect questions are usually answered from a memorised list of defect names rather than a cause-remedy chain. Candidates have not practised the diagnostic sequence of when the defect appeared (during application, during drying, in service) and where it is located.
What to do instead
Use a fixed three-step template for every defect answer: (1) describe the appearance precisely, (2) state the most probable cause linked to a process stage, (3) give the corrective action plus the preventive action. Practise with blistering, blooming, wrinkling, orange peel, and chalking, forcing each into the template so cause and remedy are never confused with the name.
Candidates treat spray gun faults as a single 'gun problem' and cannot separate fluid-flow faults from air-flow faults, so they answer 'increase pressure' for a spitting gun, a fan pattern with tails, or a dry overspray haze alike.
The interaction of fluid needle, fluid tip, air cap, and atomising pressure is taught as a diagram but rarely as a troubleshooting tree. Candidates memorise 'high pressure is good' without knowing the symptoms of excessive atomising pressure (dry overspray, bounce-back) versus insufficient pressure (large droplets, poor fan).
What to do instead
Learn a two-branch decision tree. Fluid-side symptoms: spitting, pulsating, or heavy centre pattern point to a loose or dirty fluid tip, clogged strainer, or low fluid supply. Air-side symptoms: tails at fan edges, dry spray, or excessive fog point to wrong air cap, blocked horn holes, or pressure too high. Practise matching six symptom descriptions to a branch and a component before choosing an action.
On estimation questions, candidates compute paint quantity from the total surface area without deducting openings, without applying the number of coats, and without converting litres to the coverage given in square metres per litre per coat.
Area calculation and material calculation are learned as separate skills, and word problems are read quickly. The phrase 'two coats' is treated as decoration rather than a multiplier, and spreading rate is used as a total rather than a per-coat figure.
What to do instead
Adopt a written four-line working: gross area, minus openings, times number of coats, divided by spreading rate, then add a stated wastage allowance. Write the units on every line (m2, coats, m2/L, L). Do three full worked examples including one with doors and windows deducted and one where the primer and finish have different spreading rates.
Candidates apply the wrong first-aid priority for chemical exposure, for example inducing vomiting after ingestion of a solvent-based paint, or rubbing solvent into the eye, or using a dry cloth to wipe a spill on skin before flushing.
First aid is studied as a list of steps detached from the specific hazard classes of paints, thinners, and hardeners. The general rule 'flush with water' is remembered, but the exceptions for hydrocarbons, corrosive hardeners, and eye contamination are not distinguished.
What to do instead
Group hazards by route of entry (skin, eye, inhalation, ingestion) and learn the one controlling action for each: copious water flushing for eyes and skin, fresh air and removal from exposure for inhalation, and for solvent ingestion never induce vomiting but seek medical help with the safety data sheet. Rehearse with three scenario questions and always state the SDS and medical referral step.
Candidates confuse the reading of a steel rule or vernier calliper by counting the smallest division wrongly, or they read the vernier coincidence line on the wrong scale, giving a measurement that is out by one main-scale division.
Measuring instrument questions are answered from memory of a diagram rather than from practice with the actual scale. The difference between the main scale and the vernier scale, and the least count of each instrument, is not firmly attached to a number.
What to do instead
Memorise least counts as facts (steel rule typically 0.5 mm, vernier calliper 0.02 mm for a 50-division vernier, micrometer 0.01 mm) and practise reading three given values in each instrument, stating main-scale reading plus vernier division times least count. Always quote the unit and check the reading is plausible for the object size.
When matching or mixing a colour, candidates add the hue that is visually dominant in the target (adding more red to a red that is already too red) instead of adding the complementary or the missing component, and they judge the match under tungsten workshop light.
Colour theory is learned as a wheel diagram without the practical rule that you correct a cast by moving toward its complement. Metamerism and the effect of light source on a match are rarely demonstrated, so candidates trust a match made under the wrong illuminant.
What to do instead
Learn the correction rule: if the mix is too red, add a little green-side or reduce red, never more red; correct a blue cast with a touch of orange, and so on, adding in small increments. Always check the match under daylight or a standard illuminant and compare wet against a dried sample, since paint darkens or lightens on drying. Practise three cast-correction scenarios and name the complement each time.
Candidates describe surface preparation as 'clean the surface' without specifying the standard, the method, and the profile, so they cannot distinguish hand-tool cleaning from power-tool cleaning from abrasive blast cleaning when a specification calls for a defined surface condition.
Preparation is treated as a preliminary chore rather than a measurable stage. The grading of surface cleanliness and the anchor pattern needed for adhesion are not linked in the candidate's mind to coating performance.
What to do instead
Learn preparation as a specification with three parts: method (hand, power tool, blast), grade achieved (bare metal, tightly adherent rust permitted, etc.), and profile or roughness required for the coating. For each substrate, state the preparation and the reason (e.g. blast to a defined profile to give mechanical key and remove mill scale). Answer preparation questions by naming method, grade, and profile rather than 'clean and dry'.
Candidates answer employability and communication items with generic slogans ('teamwork is important', 'safety first') instead of the specific behaviour asked for, and they mis-handle basic computer items such as file extensions, save versus save-as, or the purpose of a spreadsheet cell reference.
These domains are perceived as low-value and are revised last or not at all. The questions ask for concrete behaviours and definitions, but candidates fall back on remembered phrases from induction talks, and computer terms are learned by clicking without naming the concept.
What to do instead
Convert each soft-skill topic into two or three concrete behaviours with an example (for teamwork: report a defect to the supervisor before the next coat rather than covering it; for communication: confirm a verbal instruction in writing). For computer basics, learn the definitions of file, folder, extension, save versus save-as, and cell reference, and practise explaining each in one sentence without using the mouse.