19 Spray Gun & Air Supply Practice Questions & Answers

Every Spray Gun & Air Supply practice question from the ASE B2 Painting & Refinishing Practice Test, with the correct answer and a short explanation.

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1. A painter is setting up a spray gun for the next product to be applied. Which factor should primarily determine the fluid nozzle and needle size?
- A.The painter's preference, using one tip size for all products
- B.The type of coating being sprayed, as listed on that product's TDS✓ Answer
- C.The size of the repair area, with larger tips for full panels
- D.The booth design, with larger tips used in downdraft booths
Fluid tip and needle size are matched to the viscosity and solids of the coating: thin basecoat and clear atomize well through a smaller tip, while high-build primer-surfacer and spray filler need a larger one. The product's technical data sheet states the recommended setup; job size, booth type and habit do not change what the material needs.
Ref QB-4M4XUWSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Spray Gun Operation and Related Equipment); paint manufacturer technical data sheet practiceReport a problem with this question
2. A painter is switching a gun from clearcoat to a high-build primer-surfacer. Painter A says the needle, fluid tip and air cap should be changed together as a matched set. Painter B says the high-build primer-surfacer generally calls for a larger fluid tip than the clearcoat. Who is right?
- A.A only
- B.B only
- C.Neither A nor B
- D.Both A and B✓ Answer
Both are right. The needle, fluid tip and air cap are designed as a matched set, so mixing sizes gives poor sealing and a distorted pattern. Thicker, higher-solids materials such as high-build primer-surfacer need a larger fluid tip than clearcoat; the exact size comes from the product's TDS.
Ref QB-K4XR9WSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Spray Gun Operation and Related Equipment); spray gun manufacturer setup guidanceReport a problem with this question
3. During a static pattern test on masking paper, an HVLP gun leaves a pattern that is heavy at both ends and thin in the center. Which adjustment is most likely to correct it?
- A.Add extra reducer so the material spreads into the thin center
- B.Open the pattern control valve fully to widen the fan further
- C.Lower the atomizing air pressure or open the fluid control knob✓ Answer
- D.Raise the atomizing air pressure and close down the fluid control knob
A split pattern means there is too much atomizing air for the amount of fluid, or the fan is opened too wide, so the air pushes material out to the ends. Lowering air pressure, increasing fluid flow or narrowing the fan rebalances it. Raising pressure, thinning the material or widening the fan all make the split worse.
Ref QB-3MRKPVSource: Spray gun manufacturer spray-pattern troubleshooting charts; ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Spray Gun Operation and Related Equipment)Report a problem with this question
4. A static pattern test shows a heavy, wet center with starved, light ends. Painter A says the atomizing air pressure may be too low for the material. Painter B says the pattern (fan) control valve is probably opened too wide. Who is right?
- A.B only
- B.Neither A nor B
- C.Both A and B
- D.A only✓ Answer
Only Painter A is right. A heavy-center pattern comes from too little atomizing air, material that is too thick, too much fluid flow, or a fan set too narrow. A fan opened too wide produces the opposite fault, a split pattern with heavy ends.
Ref QB-P4ZRSZSource: Spray gun manufacturer spray-pattern troubleshooting charts; ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Spray Gun Operation and Related Equipment)Report a problem with this question
5. A gun sprays a crescent-shaped pattern. The painter rotates the air cap 180 degrees and sprays again, and the crescent now curves the opposite way. What is the most likely fault?
- A.A worn fluid needle packing that lets air into the paint
- B.Dried paint built up on one side of the fluid tip
- C.Dried paint partly blocking a horn hole in the air cap✓ Answer
- D.An inlet air pressure set too low at the gun regulator
Rotating the air cap 180 degrees isolates the fault: if the defect moves with the cap, the cap is the cause, and a crescent comes from a partly clogged horn hole on one side. Soak the cap and clear the hole with a soft brush or wooden or plastic pick. If the defect had stayed in place, the fluid tip would be the cause.
Ref QB-6MTK7ZSource: Spray gun manufacturer spray-pattern troubleshooting charts (air cap rotation test)Report a problem with this question
6. A gun sprays a teardrop pattern that is heavy at the top. After the air cap is rotated 180 degrees, the heavy area stays at the top. Painter A says the air cap horn holes should be cleaned because the cap is the cause. Painter B says the fluid tip should be inspected for dried paint or damage. Who is right?
- A.Neither A nor B
- B.B only✓ Answer
- C.A only
- D.Both A and B
Only Painter B is right. When the defect stays in the same position after the air cap is turned 180 degrees, the cap is not the cause; the fault lies in the fluid tip, typically dried paint on the tip or a damaged tip. A fault that followed the cap would point to the cap instead.
Ref QB-N4NEMYSource: Spray gun manufacturer spray-pattern troubleshooting charts (air cap rotation test)Report a problem with this question
7. A painter needs a narrower pattern to coat a door jamb while keeping the gun otherwise set up for the same material. Which control should be adjusted to narrow the fan?
- A.The fluid control knob, which shortens needle travel to narrow the fan
- B.The pattern control valve, which cuts horn air to narrow the fan✓ Answer
- C.The wall regulator, which lowers inlet pressure to narrow the fan
- D.The air cap position, which turns the horns sideways to narrow the fan
The pattern (fan) control valve meters air to the horn holes, which flatten the spray into a fan; less horn air gives a narrower, rounder pattern. The fluid knob limits needle travel and so controls fluid volume, the regulator sets atomizing pressure, and turning the cap only changes the fan's orientation, not its width. A narrower fan usually needs less fluid as well to avoid runs.
Ref QB-5MF92YSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Spray Gun Operation and Related Equipment); spray gun manufacturer operating instructionsReport a problem with this question
8. An HVLP gun's technical data sheet lists a required inlet pressure. Painter A says to verify it with a gauge or digital regulator at the gun inlet while the trigger is pulled. Painter B says the wall regulator reading with the gun idle is accurate enough because hose loss is negligible. Who is right?
- A.A only✓ Answer
- B.B only
- C.Neither A nor B
- D.Both A and B
Only Painter A is right. HVLP guns consume a large air volume, so hoses, couplers and filters cause a real pressure drop once air is flowing. A reading taken at the gun inlet with the trigger pulled shows the pressure the gun actually receives; a static wall reading overstates it.
Ref QB-R4QE54Source: Spray gun manufacturer operating instructions (dynamic inlet pressure); ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Spray Gun Operation and Related Equipment)Report a problem with this question
9. An HVLP gun atomizes well on a short hose near the regulator but poorly at the far end of the shop. All of these could reduce the air reaching the gun EXCEPT:
- A.A 3/8 in inside-diameter hose with high-flow couplers✓ Answer
- B.A partly clogged filter element in the air line
- C.A long run of 1/4 in inside-diameter air hose to the gun
- D.Standard quick couplers with small internal bores
HVLP guns need high air volume, so anything that restricts flow — small-diameter or long hoses, standard couplers with small bores, or a clogged filter — drops the pressure at the gun. A 3/8 in or larger hose with high-flow couplers is the recommended remedy, not a cause of the problem.
Ref QB-8MH9J3Source: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (adequacy of air hoses, regulator and air lines); spray gun manufacturer air-supply guidanceReport a problem with this question
10. A shop is adding a branch drop from the main air line to a new spray station. Where should the branch line connect to the main line?
- A.To the top of the main line, so condensed water stays in the main below✓ Answer
- B.To the side of the main line, so the branch stays level with the main
- C.To the far end of the main line, so moisture runs out at that station
- D.To the bottom of the main line, so water drains toward the gun filter
Condensed water runs along the bottom of the main line, so branch lines take air off the top (a gooseneck) to leave that water behind. The main line slopes back toward the compressor or a drain, with drop legs and drains at the low points. Connecting at the bottom or the end sends water straight toward the gun.
Ref QB-ZEX8TGSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (air lines and air source); compressed-air system installation practiceReport a problem with this question
11. Oil or water carried through the compressed-air supply into the spray gun can cause all of these EXCEPT:
- A.A crescent pattern from a part-clogged horn hole✓ Answer
- B.Blistering from moisture trapped under the film
- C.Spitting as slugs of water pass through the gun
- D.Fisheyes where oil droplets reach the fresh film
Oil in the air supply causes fisheyes and poor adhesion, and water causes blistering, spitting and adhesion loss; that is why tanks and filter bowls are drained daily and coalescing filters and dryers are used. A crescent pattern is a mechanical fault from a partly clogged air cap horn hole, not air contamination.
Ref QB-HX4EDHSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (air source and filtration unit); I-CAR refinish training principlesReport a problem with this question
12. A painter is cleaning a solventborne gun at the end of the day. Painter A says the whole gun can be soaked overnight in lacquer thinner to loosen dried paint. Painter B says clogged horn holes should be opened with a fine wire or a small drill bit. Who is right?
- A.Both A and B
- B.A only
- C.Neither A nor B✓ Answer
- D.B only
Neither is right. Soaking the whole gun strips lubricant and swells or damages the packings and seals; only the air cap and removable parts are soaked. Wire or a drill bit can enlarge or nick the precision horn holes and permanently distort the pattern, so a soft brush or a wooden or plastic pick is used instead.
Ref QB-YEKWMFSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (clean and maintain spray guns); spray gun manufacturer cleaning instructionsReport a problem with this question
13. A painter has just finished spraying waterborne basecoat. Which cleaning practice is correct?
- A.Flush with a waterborne gun cleaner through a gun with stainless passages✓ Answer
- B.Flush with lacquer thinner first to cut the resin, then rinse with water
- C.Soak the whole gun in solvent gun wash so that every passage is cleaned
- D.Flush with solventborne basecoat reducer, since it dissolves any paint
Waterborne material is cleaned with a waterborne gun cleaner, and the gun should have stainless steel fluid passages so water does not corrode it. Putting solvent into wet waterborne paint can coagulate it into a gummy mass that clogs passages, and soaking the whole gun damages its seals.
Ref QB-GXR38GSource: Paint manufacturer waterborne basecoat technical data sheet practice; ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Spray Gun Operation and Related Equipment)Report a problem with this question
14. A gravity-feed gun spits and sprays intermittently during a coat. All of these are likely causes EXCEPT:
- A.A loose fluid tip or a damaged fluid tip seat in the gun
- B.A paint level in the cup too low to keep the outlet covered
- C.A clogged vent hole in the lid of the gravity-feed cup
- D.A fan width set slightly narrower than the painter's usual✓ Answer
Spitting happens when air gets into the fluid stream or the flow is interrupted: low material in the cup, a loose or damaged fluid tip seat, worn needle packing, a blocked cup vent or debris in the passage. A slightly narrower fan changes pattern width but does not make the gun spit.
Ref QB-XE8KFESource: Spray gun manufacturer troubleshooting charts (spitting and fluttering); ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (Spray Gun Operation and Related Equipment)Report a problem with this question
15. A clearcoat TDS calls for a bake of 30 minutes at 140°F metal temperature after the specified flash. When should the painter start timing the 30 minutes?
- A.When the last coat goes on, so that the flash time counts toward the bake
- B.When the burner lights and the booth controls switch over into bake mode
- C.When the booth's air temperature display first reads 140°F on the controls
- D.When the panel surface reaches 140°F, checked with a surface thermometer✓ Answer
A bake specification given as metal temperature is met only when the panel itself reaches that temperature, which lags well behind the burner and the booth air. Timing from burner start or air temperature undercures the film. The flash period is a separate step that must be completed before the bake begins.
Ref QB-FXDR2FSource: Paint manufacturer technical data sheet practice (bake schedule by metal temperature); ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (force-dry sprayed materials)Report a problem with this question
16. A painter is force-drying primer-surfacer with a short-wave infrared lamp. Painter A says placing the lamp closer than the specified distance can cause blistering, solvent popping or discoloration. Painter B says infrared heats the substrate so the film cures from the inside out, helping solvents escape. Who is right?
- A.B only
- B.Both A and B✓ Answer
- C.Neither A nor B
- D.A only
Both are right. Infrared energy passes through the film and heats the substrate, so curing proceeds from the substrate outward and solvent can escape before the surface seals. Too close or too long overheats the panel and causes blistering, solvent popping, lifting or discoloration, so the specified distance, flash time and a surface thermometer are used.
Ref QB-WEV8ADSource: Infrared curing equipment manufacturer operating instructions; ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (force-dry sprayed materials)Report a problem with this question
17. A shop begins using a UV-cure primer with a UV-A lamp. Painter A says areas shadowed by a body line will still cure fully from heat conducted out of the lit areas. Painter B says the operator needs UV-blocking eye and skin protection while the lamp is on. Who is right?
- A.A only
- B.Neither A nor B
- C.B only✓ Answer
- D.Both A and B
Only Painter B is right. UV-cure products are cured by the light itself, not by heat, so any shadowed area that the lamp does not reach stays uncured and soft; the lamp must be repositioned. UV-A exposure can harm the eyes and skin, so UV-blocking eyewear and skin coverage are required.
Ref QB-EX2EVDSource: UV-cure primer manufacturer technical data sheet practice; ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (force-dry sprayed materials)Report a problem with this question
18. A painter switches from a gravity-feed cup to a siphon-feed cup setup. Which statement about the siphon-feed setup is correct?
- A.The cup can take any air cap, since siphon and pressure caps interchange
- B.The cup must be vented, and it uses a siphon-type (external-mix) air cap✓ Answer
- C.The cup must be sealed airtight, and it uses a pressure-feed air cap
- D.The cup empties fully, and it needs a lower inlet pressure than gravity
A siphon cup works because air flowing across the siphon air cap creates low pressure that draws paint up, so atmospheric air must enter through the cup vent; a blocked vent starves the gun. Siphon caps and pressure-feed caps are designed differently and are not interchangeable, and siphon feed needs more pressure and leaves material in the cup.
Ref QB-5FCKGNSource: ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (select correct spray gun, needle, fluid tip and air cap); spray gun manufacturer literatureReport a problem with this question
19. On a humid day, waterborne basecoat is flashing slowly between coats. Which equipment approach best speeds the flash without risking the finish?
- A.Bring an infrared lamp in close at full power right after each basecoat coat
- B.Add solventborne reducer to the waterborne basecoat to speed its evaporation
- C.Increase air movement over the panel with blowers or the booth's airflow system✓ Answer
- D.Run the booth up to full bake temperature between each coat of the basecoat
Waterborne basecoat dries by evaporation of water, and humid air slows that evaporation; moving more air across the surface carries the moisture away and is the method waterborne systems are designed around. Full bake heat or close, full-power infrared before the flash is complete can skin the surface and trap water, and solvent reducer is incompatible with waterborne paint.
Ref QB-NXHR3PSource: Paint manufacturer waterborne basecoat technical data sheet practice; ASE Collision Repair and Refinish Study Guide, Test B2 Painting and Refinishing task list (force-dry sprayed materials, airflow)Report a problem with this question

1. A painter is setting up a spray gun for the next product to be applied. Which factor should primarily determine the fluid nozzle and needle size?

2. A painter is switching a gun from clearcoat to a high-build primer-surfacer. Painter A says the needle, fluid tip and air cap should be changed together as a matched set. Painter B says the high-build primer-surfacer generally calls for a larger fluid tip than the clearcoat. Who is right?

3. During a static pattern test on masking paper, an HVLP gun leaves a pattern that is heavy at both ends and thin in the center. Which adjustment is most likely to correct it?

4. A static pattern test shows a heavy, wet center with starved, light ends. Painter A says the atomizing air pressure may be too low for the material. Painter B says the pattern (fan) control valve is probably opened too wide. Who is right?

5. A gun sprays a crescent-shaped pattern. The painter rotates the air cap 180 degrees and sprays again, and the crescent now curves the opposite way. What is the most likely fault?

7. A painter needs a narrower pattern to coat a door jamb while keeping the gun otherwise set up for the same material. Which control should be adjusted to narrow the fan?

9. An HVLP gun atomizes well on a short hose near the regulator but poorly at the far end of the shop. All of these could reduce the air reaching the gun EXCEPT:

10. A shop is adding a branch drop from the main air line to a new spray station. Where should the branch line connect to the main line?

11. Oil or water carried through the compressed-air supply into the spray gun can cause all of these EXCEPT:

12. A painter is cleaning a solventborne gun at the end of the day. Painter A says the whole gun can be soaked overnight in lacquer thinner to loosen dried paint. Painter B says clogged horn holes should be opened with a fine wire or a small drill bit. Who is right?

13. A painter has just finished spraying waterborne basecoat. Which cleaning practice is correct?

14. A gravity-feed gun spits and sprays intermittently during a coat. All of these are likely causes EXCEPT:

15. A clearcoat TDS calls for a bake of 30 minutes at 140°F metal temperature after the specified flash. When should the painter start timing the 30 minutes?

17. A shop begins using a UV-cure primer with a UV-A lamp. Painter A says areas shadowed by a body line will still cure fully from heat conducted out of the lit areas. Painter B says the operator needs UV-blocking eye and skin protection while the lamp is on. Who is right?

18. A painter switches from a gravity-feed cup to a siphon-feed cup setup. Which statement about the siphon-feed setup is correct?

19. On a humid day, waterborne basecoat is flashing slowly between coats. Which equipment approach best speeds the flash without risking the finish?

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