The Language of Finishing: Paint and Coatings Glossary G–H

Practical definitions for galvanizing, gloss, grounding, spray-gun operation, high-performance coatings, inspection, and surface preparation.

This installment of The Language of Finishing covers industry terms beginning with G and H. The definitions apply across automotive refinishing, OEM production, aerospace and aviation, rail, marine, protective coatings, powder coating, electrocoat, floor coatings, roof coatings, linings, wood finishing, and other professional coating sectors.

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G

Galvanic Corrosion

Industry areas: Protective Coatings, Marine, Aerospace, Automotive, OEM

Galvanic corrosion can occur when dissimilar metals are electrically connected in the presence of an electrolyte, such as water containing salts. The more active metal may corrode preferentially.

Coating selection, electrical isolation, joint design, drainage, sealants, and material compatibility can help manage the risk.

Galvanized Steel

Industry areas: Structural Steel, OEM, Powder Coating, Architectural Metal

Galvanized steel is steel protected by a zinc coating. The zinc provides barrier protection and can also provide sacrificial protection to exposed steel.

Galvanized steel may require cleaning, removal of passivation treatments, weathering, chemical preparation, or light abrasive blasting before painting. The correct procedure depends on the galvanizing process, surface condition, and coating system.

Galvanizing

Galvanizing is the application of zinc to iron or steel for corrosion protection. Common methods include hot-dip galvanizing and continuous sheet galvanizing.

The appearance and surface condition can vary according to the galvanizing process, steel chemistry, cooling, handling, weathering, and post-treatment.

Gage and Gauge

Industry areas: Inspection, Application Equipment, Process Control

Gage and gauge are alternative spellings for an instrument used to measure or indicate a physical property. ASTM coating standards frequently use the spelling “gage,” while equipment manufacturers and general industry often use “gauge.”

Examples include pressure gauges, wet-film gauges, dry-film thickness gauges, and vacuum gauges.

Gauge Pressure

Gauge pressure is pressure measured relative to surrounding atmospheric pressure. A pressure gauge reading of zero normally indicates that the measured pressure is equal to local atmospheric pressure.

Gauge pressure differs from absolute pressure, which uses a perfect vacuum as its reference.

Gassing

Industry areas: Powder Coating, Castings, Galvanized Steel, Concrete Coatings

Gassing is the release of air, moisture, or another gas from the substrate or coating during heating, application, or cure. It may produce bubbles, pinholes, craters, or blisters.

Gassing is commonly associated with porous castings, galvanized surfaces, concrete, trapped contamination, and parts containing seams or voids.

Gel Coat

Industry areas: Composites, Marine, Transportation, Fiberglass Products

A gel coat is a pigmented or clear resin layer applied to a mold or composite surface to provide appearance, weather resistance, water resistance, and surface protection.

Gel-coat application requires control of material preparation, catalyst ratio, film thickness, spray technique, mold condition, and cure.

Gel Time

Industry areas: Plural-Component Coatings, Floor Coatings, Linings, Composites

Gel time is the interval required for a reactive material to reach a gel-like state under specified conditions.

Gel time is affected by material temperature, ambient temperature, mixing ratio, batch size, catalyst level, and product chemistry. It should not automatically be treated as identical to pot life or working time.

Generic Coating Type

A generic coating type identifies a broad family of coatings based on binder or curing technology, such as epoxy, acrylic, alkyd, polyurethane, polysiloxane, or zinc-rich coating.

Products within the same generic family can have very different application requirements and performance. A generic description does not replace the manufacturer’s product data.

Glass-Flake Coating

Industry areas: Linings, Marine, Chemical Processing, Offshore

A glass-flake coating contains thin glass flakes that align within the coating film and create a more difficult path for moisture, chemicals, and gases to reach the substrate.

These high-build systems may require specialized mixing, pumping, spray equipment, thickness control, and holiday inspection.

Gloss

Industry areas: Automotive, Aerospace, OEM, Architectural, Wood Finishing

Gloss is the visual impression associated with the way a surface reflects light, particularly in a mirror-like direction. Surface smoothness, coating chemistry, color, texture, film thickness, cure, and application affect perceived gloss.

Terms such as flat, matte, eggshell, satin, semigloss, and high gloss are descriptive categories, but their numerical ranges can vary among manufacturers.

Gloss Meter

A gloss meter measures specular reflection at a specified geometry. Common measurement angles include 20, 60, and 85 degrees.

Results should identify the measurement angle, instrument, calibration standard, surface condition, and test procedure. ASTM D523 covers the measurement of specular gloss.

Gloss Retention

Gloss retention is a coating’s ability to maintain its original gloss during weathering, cleaning, chemical exposure, ultraviolet exposure, or service.

It is commonly expressed by comparing gloss after exposure with the original measured value. Good gloss retention does not necessarily prove that all protective properties remain unchanged.

Graffiti-Resistant Coating

Industry areas: Architectural, Transit, Rail, Public Infrastructure

A graffiti-resistant coating is designed to reduce the adhesion of graffiti materials or permit their removal without unacceptable damage to the underlying finish.

Systems may be permanent, renewable, or sacrificial. Cleaning products and procedures must be compatible with the selected coating.

Gravity-Feed Spray Gun

Industry areas: Automotive Refinish, Wood Finishing, Aerospace, General Industrial

A gravity-feed spray gun positions the material cup above the gun so gravity assists coating flow into the fluid nozzle.

Gravity feed can operate with relatively low fluid pressure and small quantities of material. Cup connection, venting, fluid-nozzle size, gun angle, and coating viscosity affect performance.

Grit

Industry areas: Abrasive Blasting, Sanding, Surface Preparation

Grit can refer to angular abrasive-blasting media or to the particle-size designation of coated abrasives such as sandpaper.

The same grit number should not be assumed to produce identical results across different abrasive types, manufacturers, or preparation methods.

Grit Blasting

Grit blasting uses angular abrasive particles propelled against a surface to remove contamination and produce a profile.

The resulting cleanliness and profile depend on abrasive type, particle size, shape, velocity, angle, nozzle distance, and the original surface condition.

Grinding

Industry areas: Surface Preparation, Concrete Coatings, Metal Fabrication

Grinding uses an abrasive wheel, disc, or other powered tool to remove coating, corrosion, laitance, weld irregularities, or substrate material.

Grinding can smooth sharp edges and welds or produce a surface texture. It may also polish or smear contamination if the wrong tool, pressure, or abrasive is used.

Ground

Industry areas: Electrostatic Application, Electrical Safety, Powder Coating

An electrical ground is a conductive connection to earth or another approved reference intended to safely carry electrical charge.

In electrostatic coating, the workpiece, booth, equipment, containers, and other conductive objects may require effective grounding in accordance with applicable codes and equipment instructions.

Ground Continuity

Ground continuity is the presence of a continuous conductive path between an object and the grounding point.

Visual contact between a part and a hook does not prove effective grounding. Coating buildup, corrosion, dirt, loose connections, and worn contact points can increase resistance.

Grounding

Grounding is the act of connecting conductive equipment, workpieces, containers, or structures to an approved electrical ground.

Effective grounding helps control static charge, supports electrostatic transfer, and reduces shock and ignition hazards. Grounding and bonding are related but distinct electrical-safety practices.

Grounding Strap

A grounding strap is a conductive strap, cable, or assembly used to connect equipment or a workpiece to ground.

It must be properly sized, securely connected, protected from damage, and inspected according to the equipment manufacturer’s instructions and applicable requirements.

Guide Coat

Industry areas: Automotive Refinish, Aerospace, Surface Preparation

A guide coat is a thin contrasting material applied over primer, filler, or another surface to reveal low spots, scratches, pinholes, and other irregularities during sanding.

The guide coat is removed as the surface is sanded and is not normally intended to remain as a functional coating layer.

Gun Distance

Industry areas: All Spray Application

Gun distance is the distance between the spray-gun tip or air cap and the surface being coated.

Excessive distance can increase overspray, dry spray, and material loss. Holding the gun too close can create runs, excessive build, poor pattern development, or uneven coverage. The correct distance depends on spray technology, coating, pressure, tip, and part geometry.

Gun Extension

A gun extension increases the reach of a spray gun or positions the spray head away from the gun body. Extensions may be straight, angled, fixed, or specialized for internal surfaces.

Length and design affect balance, triggering, fluid flow, pressure loss, atomization, cleaning, and safe operation.

Gun Technique

Gun technique is the way an operator positions and moves a spray gun. It includes distance, angle, travel speed, overlap, triggering, stroke direction, and handling around edges and complex shapes.

Good equipment cannot compensate completely for poor technique. Consistent gun movement is essential for uniform film thickness and appearance.

Gun Washer

Industry areas: Automotive Refinish, Industrial Finishing, Maintenance

A gun washer is equipment designed to clean spray guns and related components using solvent, water, or another approved cleaning fluid.

The cleaning process must be compatible with the gun, seals, coating, and environmental requirements. Electrostatic equipment requires special attention to electrical and manufacturer restrictions.

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H

Hand-Tool Cleaning

Industry areas: Maintenance Painting, Protective Coatings, Field Repair

Hand-tool cleaning uses nonpowered tools such as scrapers, wire brushes, chisels, and sandpaper to remove loose rust, loose coating, and other surface contamination.

It is generally slower and less aggressive than power-tool or abrasive-blast cleaning. Hand-tool cleaning does not automatically remove tightly adherent mill scale, coating, or deeply embedded contamination.

HAP — Hazardous Air Pollutant

Industry areas: Environmental Compliance, OEM, Spray Finishing

HAP means hazardous air pollutant. HAPs, also called air toxics, are substances regulated because they are known or suspected to cause serious health or environmental effects.

Coating operations may be subject to HAP-content, emission, recordkeeping, work-practice, or control requirements. The U.S. Environmental Protection Agency maintains information about regulated hazardous air pollutants.

Hardener

Industry areas: Automotive Refinish, Epoxies, Polyurethanes, Floor Coatings

A hardener is a component mixed with certain coatings to produce the intended chemical cure. It may also be called an activator, converter, or curing agent, depending on the product.

The specified mixing ratio must be followed. Adding extra hardener does not necessarily make the coating cure faster or become harder and can damage performance.

Hardness

Industry areas: OEM, Automotive, Aerospace, Floors, Wood Finishing

Hardness is a coating’s resistance to indentation, scratching, gouging, or another defined deformation.

Different hardness tests measure different responses and should not be treated as interchangeable. ASTM D3363 covers a pencil method for evaluating coating-film hardness.

Hazardous Location

Industry areas: Spray Booths, Mixing Rooms, Powder Coating, Electrical Safety

A hazardous location is an area where flammable gases, vapors, combustible dusts, or ignitable fibers may be present in quantities requiring specially designed electrical equipment and wiring.

The classification depends on the material, likelihood of presence, and applicable electrical code. Equipment must be approved and marked for the specific classification.

Heat Cure

Industry areas: Powder Coating, OEM, Automotive, E-Coat

Heat cure uses elevated temperature to initiate, accelerate, or complete a coating’s curing reaction.

The required cure is often based on part-metal temperature and time at temperature—not simply oven-air temperature.

Heat Resistance

Industry areas: Industrial, Aerospace, Automotive, Ovens, Exhaust Systems

Heat resistance is a coating’s ability to tolerate elevated temperature without unacceptable softening, discoloration, cracking, detachment, decomposition, or loss of protection.

Continuous-service and intermittent-service temperature ratings may be different.

Heater

Industry areas: Plural-Component Spray, High-Viscosity Coatings, Ovens

A heater raises the temperature of coating, air, water, or another process material. Fluid heaters can reduce viscosity and improve atomization or pumping.

Heating also shortens pot life and accelerates reaction in many plural-component coatings. Temperature and pressure ratings must not be exceeded.

Hiding

Industry areas: Automotive, Architectural, OEM, Wood Finishing

Hiding is a coating’s ability to obscure the color, pattern, or appearance of the substrate or previous coat.

Hiding depends on pigmentation, color contrast, applied thickness, application method, surface texture, and lighting. Visual hiding does not prove that the specified film thickness has been achieved.

High-Build Coating

Industry areas: Protective Coatings, Linings, Marine, Floors

A high-build coating is designed to produce relatively high dry-film thickness in one or a limited number of coats.

High-build coatings can reduce the number of application steps, but excessive thickness may produce sagging, cracking, solvent retention, incomplete cure, or stress.

High-Pressure Airless Spray

Industry areas: Protective Coatings, Roof Coatings, Marine, Construction

High-pressure airless spray atomizes coating by forcing it through a small tip orifice at high fluid pressure without adding compressed atomizing air at the gun.

It is commonly used for high production and high-solids protective coatings. High-pressure injection injury is a medical emergency, even when the injury initially appears minor.

High-Solids Coating

Industry areas: Protective Coatings, OEM, Marine, Linings

A high-solids coating contains a relatively high proportion of nonvolatile material compared with conventional coatings of the same general type.

High solids can provide greater dry-film thickness with less volatile loss, but the material may require careful control of temperature, mixing, atomization, pressure, and film build.

High-Transfer-Efficiency Application

High-transfer-efficiency application refers to equipment or methods designed to increase the percentage of coating deposited on the intended workpiece.

HVLP, electrostatic application, rotary atomization, properly controlled air-assisted airless, and automated application may improve transfer efficiency. Actual results depend on the complete process and operator technique.

Hold Point

Industry areas: Inspection, Quality Assurance, Protective Coatings, Aerospace

A hold point is a defined stage of work that cannot proceed until a required inspection, test, review, or approval has been completed.

Examples include acceptance of surface preparation before priming or final holiday testing before equipment is placed into service.

Holiday

Industry areas: Linings, Pipelines, Protective Coatings, Floors

A holiday is a discontinuity in a coating film that exposes or provides a conductive path to the substrate or underlying conductive layer.

Holidays can include pinholes, voids, cracks, misses, or other openings that may be too small to see. They are especially important in immersion, lining, containment, and pipeline service.

Holiday Detector

A holiday detector is an electrical instrument used to locate discontinuities in a nonconductive coating applied over a conductive substrate.

Low-voltage wet-sponge and high-voltage spark-testing methods serve different coating thicknesses and conditions. ASTM D5162 covers discontinuity testing of nonconductive protective coatings on metallic substrates.

Hook

Industry areas: Powder Coating, Electrostatic Coating, OEM

A hook supports a part on a conveyor or rack during pretreatment, coating, and curing. In electrostatic application, the hook commonly forms part of the electrical path between the workpiece and ground.

Coating buildup on hooks can reduce grounding, change part orientation, create defects, and interfere with transfer efficiency.

Hook Mark

A hook mark is the uncoated, damaged, or visually different area where a rack or hook contacts the part.

Hook location should be considered during part and process design so the contact point does not compromise appearance, assembly, corrosion protection, or electrical performance.

Horizontal Surface

Industry areas: Protective Coatings, Floors, Roofs, Inspection

A horizontal surface is a surface oriented approximately level. Horizontal areas can collect water, dust, chemicals, debris, and excessive coating.

Their exposure and drainage conditions may make them more severe than nearby vertical surfaces.

Hose Whip

Industry areas: Airless Spray, Abrasive Blasting, Compressed Air

Hose whip is uncontrolled movement of a pressurized hose caused by a rupture, failed coupling, sudden release, or unsecured connection.

Proper hose inspection, pressure ratings, restraints, couplings, depressurization, and manufacturer-required safety devices help reduce the hazard.

Hot-Dip Galvanizing

Industry areas: Structural Steel, Infrastructure, OEM

Hot-dip galvanizing protects iron or steel by immersing it in molten zinc, producing a bonded zinc coating.

When the galvanized surface will be painted or powder coated, surface age, wet-storage stain, passivation, contamination, roughness, and preparation must be evaluated. ASTM D6386 addresses preparation of hot-dip galvanized surfaces for painting.

Hot Spray

Industry areas: Industrial Liquid Coatings, Protective Coatings, Wood Finishing

Hot spray applies coating after controlled heating to reduce viscosity and improve atomization or flow.

Heating may also shorten pot life, increase solvent evaporation, or accelerate chemical reaction. Only equipment and temperatures approved for the coating should be used.

Housekeeping

Industry areas: Spray Booths, Powder Coating, Mixing Rooms, Safety

Housekeeping is the routine control and removal of overspray, powder, dust, coating residue, contaminated rags, spills, and combustible deposits.

Good housekeeping supports finish quality, grounding, ventilation, fire prevention, worker safety, and regulatory compliance.

Humidity

Humidity is the amount of water vapor present in the air. In coating work, relative humidity is commonly measured and compared with coating-manufacturer limits.

Humidity can affect condensation risk, solvent evaporation, waterborne film formation, cure, blushing, amine blush, corrosion, and surface contamination.

Hybrid Powder Coating

Industry areas: Powder Coating, Indoor OEM Finishing

A hybrid powder coating combines two principal resin technologies, commonly epoxy and polyester, to balance appearance, application, cure, and performance.

Epoxy-polyester hybrids are widely used for interior products but generally are not selected where long-term exterior ultraviolet resistance is required.

Hydraulic Atomization

Hydraulic atomization is another term for atomization created by forcing liquid coating through a small orifice at sufficient pressure. It is the operating principle of airless spray.

The term distinguishes pressure-generated atomization from compressed-air atomization.

Hydroblasting

Industry areas: Protective Coatings, Concrete, Marine, Industrial Maintenance

Hydroblasting is a general term for cleaning or removing material with pressurized water. Depending on the industry, it may refer to pressure washing, high-pressure water cleaning, waterjetting, or hydrodemolition.

Because the term is broad, specifications should define the required pressure range, surface condition, contaminants to be removed, and acceptance standard.

Hydrophobic

Industry areas: Architectural Coatings, Concrete, Water-Repellent Treatments

Hydrophobic describes a surface or material that tends to repel water rather than readily wet or absorb it.

A hydrophobic treatment may reduce liquid-water penetration while still allowing some water-vapor transmission. Performance depends on the material, substrate, application, and exposure.

Hydrophilic

Hydrophilic describes a surface or material with an affinity for water, allowing water to spread, wet, or interact readily with it.

Hydrophilic surface behavior can affect cleaning, wetting, adhesion, condensation, and coating application.

Hydrolysis

Industry areas: Immersion Coatings, Linings, Marine, Chemical Service

Hydrolysis is a chemical reaction involving water that can break down susceptible coating components.

Long-term heat and moisture exposure can cause certain coatings to soften, lose adhesion, crack, or otherwise deteriorate through hydrolytic attack.

Hydrostatic Pressure

Industry areas: Below-Grade Coatings, Tanks, Linings, Concrete, Roofing

Hydrostatic pressure is pressure exerted by a liquid at rest due to the weight of the liquid above the point being considered.

In below-grade concrete and containment work, moisture pressure from behind a coating can contribute to blistering, delamination, and leakage.

Hygrometer

Industry areas: Coating Inspection, Application, Environmental Monitoring

A hygrometer is an instrument used to measure humidity. Modern coating inspectors commonly use electronic environmental meters, while psychrometers determine humidity using wet- and dry-bulb temperatures.

The instrument should be used, verified, maintained, and documented according to its instructions and the governing inspection procedure.

HVLP — High Volume Low Pressure

Industry areas: Automotive Refinish, Wood Finishing, Aerospace, Industrial Finishing

HVLP means high volume low pressure. An HVLP spray gun uses a relatively high volume of compressed air at controlled low air-cap pressure to atomize liquid coating.

HVLP can provide good finish quality and transfer efficiency when supplied with adequate clean, dry air and correctly matched air caps, fluid nozzles, pressure, and technique.

A gun should not be identified as HVLP solely because the inlet pressure has been reduced. HVLP performance depends on the gun’s tested design and operating limits.

Referenced Standards and Industry Resources

• ASTM D523 — Specular Gloss
• ASTM D3363 — Film Hardness by Pencil Test
• ASTM D5162 — Holiday Testing of Protective Coatings
• ASTM D6386 — Preparation of Hot-Dip Galvanized Surfaces for Painting
• U.S. EPA — Hazardous Air Pollutants
• OSHA 29 CFR 1910.107 — Spray Finishing
• AMPP — Surface Preparation Standards
• AMPP/ICRI — Surface Preparation of Concrete

Continue Exploring the Language of Finishing

This G–H installment is part of The Language of Finishing: A Paint and Coatings Industry Glossary. Additional installments will continue through the remaining alphabet, followed by a dedicated standards, organizations, and acronym index.

Technical Notice: This glossary provides general educational definitions. Terminology can vary among industries, manufacturers, standards organizations, contracts, and jurisdictions. Always consult the coating manufacturer’s current technical data sheet, safety data sheet, equipment instructions, project specification, and complete current edition of any referenced standard.

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Tags: coatings glossary G-H, galvanized steel coatings, coating gloss, spray gun technique, electrostatic grounding, coating hardness, high-build coatings, holiday detection, HVLP spray guns