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Portable Plural-Component Systems | Article 19 of 24 | Pressure and Spray Technique
Last Updated: 10/01/2026

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Portable Plural-Component Coating Systems for Contractors

Article 19 of 24

Pressure, Temperature, Spray Pattern, and Application Technique

A plural-component proportioner can deliver the correct ratio and still produce unacceptable work if pressure, temperature, tip selection, spray pattern, or gun technique is poorly controlled. Professional application requires the entire system to remain stable—from the material containers and feed pumps to the mix manifold, heated hose, spray gun, tip, and surface.

A Spray Pattern Is Evidence

The spray pattern is not merely a visual preference. It provides immediate evidence about atomization, viscosity, pressure, tip condition, material supply, pump stability, and application technique.

A properly adjusted pattern should be evenly atomized and distributed across the fan without heavy edges, fingers, tails, pulsing, excessive fog, or an unstable center. The exact appearance depends on the coating, tip, pressure, and application method.

The applicator should learn to recognize changes in the pattern before those changes become widespread film defects.

Pressure Has Several Jobs

Pressure must move each component through its individual circuit, overcome restrictions in the mix manifold and static mixer, deliver mixed material through the whip hose, and atomize the coating through the spray tip.

The required pressure is influenced by:

Material viscosity and temperature
Mix ratio and the viscosity difference between components
Feed-pump condition and inlet pressure
Pump size, speed, and mechanical condition
Filter and strainer restriction
Fluid-hose diameter, length, elevation, and condition
Mix-manifold and static-mixer restriction
Whip-hose diameter and length
Spray-tip orifice size and wear
Required production output and spray-fan quality

Pressure should be raised gradually and only to the level needed to achieve stable delivery and acceptable atomization. Excessive pressure increases overspray, rebound, hose movement, component wear, tip wear, leakage risk, and injection-injury severity.

Pressure Balance Does Not Prove Correct Ratio

The A-side and B-side pressure readings do not have to be identical. Component viscosity, pump size, meter design, restrictions, and system configuration can produce different normal pressures.

An expected pressure relationship should be established during successful startup and ratio verification. A significant change from that established relationship can warn of:

An empty or low material container
Air entering a component circuit
A blocked inlet, filter, hose, valve, mixer, or tip
A failed feed pump or proportioning pump
A leaking check valve, seal, or packing
Incorrect material temperature or viscosity
An incorrect valve position

Pressure readings are diagnostic information. Actual ratio must be established by the approved ratio-verification method.

Temperature Controls Viscosity and Flow

Heating generally lowers coating viscosity. Properly controlled heat can improve material flow, reduce the pressure needed for atomization, improve mixing, and support consistent output.

Temperature also affects chemical reaction and usable mixed-material life. Excessive heat may shorten the time available between mixing and gelation, increase reaction speed, damage temperature-sensitive materials, or cause coating defects.

Condition	Possible Effect
Material too cold	High viscosity, excessive pressure demand, poor atomization, slow pumping, cavitation, weak mixing, or heavy spray-pattern edges
Material too hot	Shortened mixed-material life, accelerated reaction, excessive misting, sagging, pinholing, or material degradation
Unequal component temperatures	Different component viscosities, unstable pressures, difficult pumping, or poor mixing
Temperature fluctuating	Changing output, pressure, fan quality, film build, and reaction rate during application

Use Approved Temperature Limits

Do not select an operating temperature simply because the equipment can reach it. The coating manufacturer must establish the permitted material-temperature range.

Confirm:

Storage and preconditioning temperature
Permitted feed-container temperature
A-side and B-side heater setpoints
Heated-hose setpoint
Maximum permitted fluid temperature
Required substrate and ambient-temperature range
Expected working time at the actual spray temperature

Temperature measured at a drum, heater outlet, or control-panel sensor may not represent the temperature at the mix manifold or spray gun. Long hose runs, wind, cold steel, hot sunlight, insulation condition, and production rate can produce meaningful temperature differences.

Selecting the Spray Tip

The spray tip helps determine both the fluid-delivery rate and fan width. Tip selection must consider the coating manufacturer’s requirements, proportioner capacity, hose configuration, surface geometry, specified film thickness, and applicator control.

Orifice size: Influences material flow and the pressure required for atomization.
Fan designation: Influences the approximate pattern width at the manufacturer’s stated test distance.
Tip condition: A worn tip may deliver more material and produce a wider, poorly controlled fan.
Tip compatibility: The tip and guard must be approved for the gun, pressure, coating, and application.

If the maximum approved pressure cannot produce an acceptable pattern, do not continue increasing pressure beyond the permitted limits. Confirm material temperature, restrictions, equipment output, and tip selection. A smaller approved orifice may atomize more effectively, but it will also change output.

Establish the Pattern at the Lowest Effective Pressure

Confirm that the materials, proportioner, temperatures, and ratio verification are acceptable.
Install the approved tip and guard using the required pressure-relief procedure.
Begin at a low fluid pressure.
Spray onto an approved test surface.
Increase pressure gradually until tails and heavy edges disappear and the fan becomes evenly atomized.
Stop increasing pressure once acceptable atomization is achieved.
Confirm output and wet-film thickness under actual application conditions.
Record the approved tip, pressures, temperatures, and test result.

The lowest effective pressure is not the lowest pressure at which material leaves the gun. It is the lowest pressure that produces the required atomization, fan stability, output, and film quality.

Reading the Spray Pattern

Pattern Condition	Possible Causes	Professional Response
Tails or fingers	Insufficient atomization pressure, material too cold, excessive viscosity, worn or incorrect tip, inadequate equipment output	Confirm temperature and system condition; increase pressure only within approved limits; verify tip selection.
Heavy center	Incorrect tip, unsuitable pressure, material characteristics, or excessive gun distance	Evaluate tip, pressure, temperature, distance, and test-surface results.
Pulsing fan	Cavitation, air in supply, low material level, unstable feed pump, restriction, proportioner problem	Stop spraying and correct the supply or equipment problem before continuing.
Excessive fog or mist	Excessive pressure, material too hot, incorrect tip, excessive distance, wind, or poor containment	Reduce pressure when possible; verify temperature, tip, distance, ventilation, and site controls.
Pattern becoming wider	Tip wear or pressure and viscosity change	Inspect the tip and verify output, pressure, temperature, and film build.
Pattern pulled to one side	Partial tip obstruction, damaged tip, contamination, or gun problem	Stop, relieve pressure, inspect, clean by the approved procedure, and replace damaged parts.

Professional Gun Technique

Good equipment cannot compensate for uncontrolled gun movement. The applicator must maintain consistent distance, angle, speed, overlap, and triggering.

Keep the Gun Perpendicular

Point the gun directly at the surface whenever geometry permits. Arcing the gun creates a heavy film in the center and a thin film at the ends of the pass. Fanning the gun at an angle can produce uneven film build and increased overspray.

Maintain a Consistent Distance

Use the distance required by the coating and equipment manufacturer. Moving too close can produce a narrow, heavy pattern with runs or excessive texture. Moving too far away can increase overspray, dry spray, material loss, and uneven film.

Move Before Triggering

Begin gun movement before pulling the trigger and release the trigger before stopping the pass. Triggering a stationary gun deposits excessive material at the beginning or end of the stroke.

Maintain Uniform Speed

Film thickness increases when the gun slows and decreases when it speeds up. Adjust the spray plan, access, staging, and crew position so the applicator can maintain a controlled movement without overreaching.

Control the Overlap

Overlap each pass by the amount required to produce uniform coverage with the selected fan. Approximately 50 percent is common for many airless applications, but the approved procedure and observed film-thickness results govern. Aim consistently at the edge or centerline established by the spray plan.

Edges, Corners, Welds, and Complex Geometry

Complex shapes interrupt the normal spray pattern. Edges and outside corners may receive less coating because part of the fan passes beyond the surface. Inside corners can receive excessive material, turbulent overspray, or poor penetration.

Apply required stripe coats before the full coat.
Use a controlled spray angle without excessively fanning the gun.
Avoid concentrating the full fan directly into an inside corner.
Use an approved smaller fan or alternate method when geometry requires it.
Inspect backsides, shadow areas, welds, bolts, stiffeners, penetrations, and difficult transitions.
Verify wet-film thickness in representative areas rather than judging coverage only by appearance.

Plan the Spray Sequence

A spray sequence should allow the applicator to maintain a wet edge, reach all surfaces safely, control overspray, and stop at logical boundaries.

Divide the work into manageable sections.
Identify start points, stop points, laps, seams, and termination areas.
Coordinate spray direction with wind and ventilation.
Apply difficult details and stripe coats in the specified sequence.
Position hoses so they do not contact uncured coating or pull the gun operator off line.
Provide sufficient access and lighting to maintain proper distance and angle.
Account for the mixed material’s working time and required flush interval.

Monitor the System During Production

Approved startup settings are a baseline, not permission to ignore the equipment during production. Monitor:

A-side and B-side pressures
A-side, B-side, and hose temperatures
Feed-pump operation and material levels
Proportioner speed and changeover behavior
Ratio, pressure, temperature, and flow alarms
Leaks at pumps, filters, hoses, manifolds, and gun connections
Spray-pattern consistency
Wet-film thickness, coverage, texture, sagging, pinholing, and overspray
Ambient, substrate, humidity, and dew-point conditions

Stop Spraying When the Process Changes

Do not spray through an unexplained change. Stop at once when any of the following occurs:

Off-ratio, pressure, temperature, or flow alarm
Unexpected pressure imbalance or pressure loss
Temperature outside the approved range
Cavitation, pump racing, surging, or loss of prime
Sudden spray-pattern or output change
Material color or consistency change
Evidence of inadequate mixing or abnormal cure
Blocked mixer, hose, gun, or tip
Material leak or damaged high-pressure component
Environmental conditions outside the specification

Mark the time and location of the last known acceptable application. Quarantine suspect work until the cause has been identified and the coating disposition has been authorized.

Production Records

Document the operating conditions that produced the accepted work:

Project, date, time, work area, and applicator
Product, component designations, and lot numbers
Proportioner and spray-gun identification
Spray-tip manufacturer, type, fan designation, and orifice
A-side and B-side pressures
A-side, B-side, and hose temperatures
Ambient, substrate, humidity, and dew-point readings
Wet-film-thickness readings and material consumption
Pattern observations and equipment adjustments
Alarms, interruptions, corrective actions, and affected areas
Start time, stop time, and completed area

Technical References and Further Study

Graco XM Plural-Component Sprayers—Operation Manual — Equipment-specific instructions for pressure and temperature limits, spray operation, alarms, ratio control, flushing, and shutdown.
WAGNER TwinControl Operating Manual — Manufacturer procedures for operating, monitoring, adjusting, flushing, and maintaining TwinControl plural-component equipment.
Graco—The Basics: An Overview of Airless Sprayers — Technical guidance on airless atomization, pattern quality, tip selection, pressure, and spray technique.
Graco—Choosing and Understanding Airless Spray Tips — General guidance concerning tip orifice, fan size, output, and tip selection.
Current coating manufacturer product data sheets, application instructions, safety data sheets, plural-component setup guides, and project specifications.

Manufacturer references are included as technical examples and educational resources. Their inclusion does not constitute a product endorsement. Use the current manual for the exact equipment model, configuration, and software version being operated.

Professional Responsibility

Plural-component spray systems may operate with hazardous, reactive, heated, flammable, sensitizing, or extremely high-pressure materials. Follow the coating and equipment manufacturers’ current written instructions, safety data sheets, pressure-relief procedures, ventilation requirements, grounding and bonding requirements, personal-protective-equipment requirements, project specifications, and applicable regulations. Equipment adjustment and application must be performed only by trained and authorized personnel.

No part of this material may be reproduced, distributed, transmitted, stored, or used in any form without prior written permission from Azimuth Spray Systems, LLC, except for brief quotations used with proper attribution.

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Tags: plural component spray pressure, coating temperature control, airless spray pattern, plural component application, industrial spray technique, spray gun distance, coating atomization

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