Paint Defects and the Additives That Prevent Them

Paint defects are faults that appear in a liquid paint or its film at one of 4 stages, in the can, in the wet film, during drying or in service, and this index sorts 15 of them. These paint film defects are listed with what each looks like, its main cause, the additive family that prevents it and the test that confirms it. Storage defects such as settling show in the can, application defects such as foaming and sagging in the wet film, drying defects such as wrinkling while the film forms, and service defects such as blocking and delamination in the dry film.

The directory groups the 15 defects in stage order: 3 storage, 6 application, 3 drying and 3 service defects. Their fixes come from 10 of the 15 families of paint additives, from defoamers and leveling agents to driers and adhesion promoters. Below the directory, the page adds 4 defects covered on additive pages, one product example with its level basis for each family, the current ASTM and ISO edition of each confirming test, a 5-step diagnosis and the EU rules that limit 4 common fixes: MEKO, octoate driers, BIT and silicone defoamers.

How we check: regulations and classifications are read at the body that issues them, standards at the standards body, and every additive level names its basis and its source; the full method is in methodology and fact-checking.

What Are Paint Defects?#

A paint defect is a visible or measurable departure of a paint or its film from specification, such as sediment in the can, sags in the wet film, wrinkles during drying or blocking in service. The specification sets the values a paint must meet, such as Krebs unit (KU) viscosity, gloss, drying time, block resistance or adhesion rating. A defect is a shortfall against one of these values, and it first shows at one stage of the paint's life, which narrows the list of causes.

Each defect has an additive side and a process side. The additive side is the family whose choice or level prevents the defect, such as a defoamer against foam or a rheology modifier against sagging. The process side covers mixing, surface preparation and application conditions. This index covers the additive side for each defect and leaves the process fixes to the individual defect pages.

The index covers defects of liquid paint formulation only: waterborne and solventborne architectural paints, wood stains and varnishes, primers and industrial liquid paints. Their defects follow from the balance of binder, pigment, solvent or water and additives, which is set out under paint formulation fundamentals. Defects of auto refinishing, art paints and powder coatings are not covered here.

All 15 Paint Defect Pages by Stage#

The 15 paint defects in the table below are grouped by stage: 3 storage defects in the can, 6 application defects in the wet film, 3 drying and film-formation defects and 3 service defects in the dry film. The table compares each defect by stage, appearance, main cause, the additive family that fixes it and the confirming test.

Read each row from left to right: the stage narrows the cause, the cause points to the additive family, and the test confirms whether the fix worked. A cell that reads "see the ... page" marks a defect whose appearance or cause is set out in full on its own page, with the process side beside the additive side.

Storage Defects in the Can#

Pigment settling appears in the can during storage because the low-shear structure of the paint is too weak to hold the pigment, and rheology modifiers of the anti-settling class prevent it. Dense pigments such as aluminum paste, micaceous iron oxide (MIO), zinc dust and anticorrosive pigments settle when that structure fails. Waterborne paints build the structure with hectorite, synthetic hectorite, attapulgite or bentonite; solventborne paints with organoclays, fumed silica, polyamide and polyolefin pastes, castor wax or urea. Syneresis is treated as part of settling on the settling page.

Viscosity loss appears in a latex paint during storage or after tinting because one ingredient breaks the thickener network, and a change of rheology modifier class prevents it. Four causes act on that network: high-HLB tinting surfactants that displace the hydrophobes of associative thickeners, the enzyme cellulase that attacks cellulose ethers, pH drift below the activation pH of alkali-swellable thickeners (ASE and HASE), and hydrophilic glycols that lower associative viscosity. The fixes follow the cause: enzyme-resistant cellulosic grades, HASE or HEUR thickeners that resist microbial and enzymatic attack, HASE added to HEUR in medium and deep tint bases, and in-can preservation.

Pigment flocculation appears in the can and the wet paint because the dispersed pigment is not stabilized well enough, so particles re-associate, and dispersants prevent it. Dispersion runs in 3 steps, wetting, mechanical breakdown and stabilization against flocculation, and a failure of the third step shows as color drift, gloss loss, a rise in viscosity, floating and flooding, or settling. One weak dispersion therefore feeds 2 other defects on this index, floating and flooding and settling.

Application Defects in the Wet Film#

Paint foaming appears during manufacture and application because air enters the paint and surfactants hold it there, and defoamers prevent it. Adams (Journal of Coatings Technology, 1998) names the sources of air as stirring and milling, filling, 2K curing reactions in urethanes, porous substrates, and roller and spray application. Emulsifiers, wetting agents and dispersants then migrate to the air-liquid interface and stabilize a surfactant-lined lamella. A 2015 CoatingsTech paper on defoaming test methods adds that zero-VOC paints need more surfactant, so a defoamer that worked in an earlier formula may no longer suffice. The same paper measures foam as air content, % air = (A - B)/A × 100, where A is the density of the unfoamed paint and B the density after shaking or stirring. Air content from the low-shear shaker method correlates with KU, and air content from the high-shear dissolver method with ICI viscosity.

Cratering and fish eyes appear as the wet film flows out, and leveling agents and wetting agents prevent them; their causes, including contamination, are set out on the cratering page. One fluorine-free, polyether-modified polydimethylsiloxane (PDMS) leveling product is described by its producer as reducing picture framing and fish eyes, and its level is in the families table below. Leveling agents also prevent orange peel, the next defect of the wet film in the directory.

Paint sagging appears on vertical surfaces when the low-shear viscosity of the wet film recovers too slowly after application, and rheology modifiers prevent it. The time the film needs to rebuild its structure after application shear is the sag window. Solventborne paints gain sag resistance from organoclays, fumed silica, castor wax, polyamide or diamide waxes and ureas; waterborne paints from hectorite, synthetic hectorite or attapulgite combined with associative thickeners. Roller spatter appears when elastic, high-molecular-weight thickener networks such as plain hydroxyethyl cellulose (HEC) break into droplets at the roller nip. Hydrophobically modified HEC (HMHEC), associative ethyl hydroxyethyl cellulose (EHEC) and Newtonian HEUR grades reduce it.

Floating and flooding appear as uneven color in the drying film because pigments of different mobility separate, and dispersants prevent them. Solvent evaporation sets up density, temperature and surface-tension gradients and Benard-cell eddies that carry the pigments apart. Two dispersant routes equalize pigment mobility: controlled-flocculating additives, at the cost of some gloss, and polymeric wetting and dispersing additives that deflocculate all pigments. Titanium dioxide must be stabilized as well, or it floats against the well-stabilized color pigments. The rub-up test confirms the defect: the still-wet film is rubbed, and the color difference between the rubbed and unrubbed area is the criterion.

Drying and Film-Formation Defects#

Surfactant leaching appears on fresh latex paint films because surfactants and other water-soluble materials migrate to the surface as water staining, and wetting agents and coalescents are the families that act on it. The ASTM practice for this defect is written for latex paint films and attributes the staining to the leaching of surfactants or other water-soluble materials. The additive side of the fix therefore sits in the surfactant load of the wetting and dispersing package.

Paint wrinkling appears while the film dries, and driers are the additive family that prevents it. Its causes are set out on the paint wrinkling page. On the additive side, one zinc drier product is claimed by its producer to prevent both wrinkling and orange peel in alkyd paints, and its level, given in % zinc metal on binder solids, is in the families table below. Every drier level on this site uses that basis, % metal on binder solids.

Loss of dry in alkyd paint is a drying defect of oxidatively curing paints, and driers are the additive family that acts on it. Drying stages and drying time are measured by ASTM D1640/D1640M-14(2022), the method used for both wrinkling and loss of dry. Both defects therefore share one additive family and one test method.

Service Defects in the Dry Film#

Paint yellowing appears in the dry film in service, and driers and neutralizers are the additive families that act on it. In waterborne paints, residual dimethylethanolamine (DMEA) and triethylamine adipate salts yellow on heating, so the choice of amine neutralizer decides part of the color stability. In alkyd paints, zirconium gives better color than other secondary driers, and aluminum driers resist yellowing. The oxidative causes of alkyd yellowing are set out on the paint yellowing page.

Blocking appears when 2 painted surfaces stick together face to face, and matting agents and waxes prevent it. ASTM D4946-89(2025) tests accelerated face-to-face blocking of architectural (trade sales) paints with a subjective rating. Industrial coatings on metal are tested by ASTM D3003 and wood finishes by ASTM D2793, so the paint class decides the method.

Paint delamination is a loss of adhesion between coats or to the substrate, and adhesion promoters and wetting agents are the additive families that act on it. Wetting agents act on the substrate side, helping the paint wet the surface it must hold to. Adhesion promoters for paint split into 2 types with their own sections on the family page: silanes and chlorinated polyolefins. The causes, from contamination to intercoat conditions, are set out on the paint delamination page.

Defects Covered on Additive Pages#

4 more paint defects are covered on the page of the additive that prevents them: skinning, flash rust, mold growth on the film and in-can spoilage. The table lists each with its stage, appearance, additive class and a product example or test.

Skinning concerns oxidatively drying paints: a solid layer forms on top of the liquid paint in the container, and waterborne paints are less prone to it (Danish EPA, 2004). Flash rust concerns waterborne paints on steel, where flash-rust inhibitors stop rust from forming while the film dries. Mold growth and in-can spoilage are the 2 biocide defects, one on the dry film and one in the container, and each has its own ASTM test.

Which Additive Families Prevent Each Defect?#

10 additive families prevent the 15 defects in the directory: defoamers, leveling agents, wetting agents, rheology modifiers, dispersants, driers, coalescents, neutralizers, matting agents and waxes, and adhesion promoters. Five defects have 2 families acting on them: cratering, orange peel, surfactant leaching, yellowing and delamination.

The table lists each family with the defects it prevents and one product example with its level basis and source.

Each example level belongs to one product and its basis, never to the family as a whole. The bases differ by family: a dispersant level is % as supplied on pigment, a drier level is % metal on binder solids, and the other examples are % as supplied on total formula. Rheology modifiers and driers each cover 4 rows of the directory: settling, viscosity loss, sagging and spatter for the first, wrinkling, loss of dry, yellowing and orange peel for the second.

Which Tests Confirm Each Defect?#

Each paint defect is confirmed by a named test, and the table below gives the current ASTM or ISO edition for 8 test groups, from sag resistance to surface tension.

Orange peel has 2 measurements by paint class: DOI gloss by ASTM D5767-18(2023) for industrial finishes and draw-down leveling by ASTM D4062-24 for architectural paints. Surfactant leaching is evaluated by ASTM D7190-10(2023), the Practice to Evaluate Leaching of Water-Soluble Materials from Latex Paint Films. Adhesion has 2 ASTM routes: tape testing by ASTM D3359-23, with Method A (X-cut) mainly for films above 125 µm (4.92 mils) and Method B (lattice) for films up to 125 µm, and pull-off testing by ASTM D4541-22 with portable testers. ASTM D3359 is similar to, but not technically equivalent to, ISO 2409. Roller spatter is rated by ASTM D4707-24.

ASTM D1309, the accelerated settling test for traffic paint, was withdrawn in 2020 and is historical only; settling is now tested by ASTM D869-21. Tests without a page of their own, such as the spatter, leaching, blocking and drying-time methods, stay in the directory row of their defect.

How to Diagnose a Paint Defect#

Diagnose a paint defect in 5 steps: note the stage at which it appears, match its appearance to a directory row, test the cause named there, change one additive at a time, and confirm the fix with the named test. The 5 steps are listed below.

1. Note the stage: in the can, in the wet film, during drying or in service.
2. Match the appearance to a row of the directory table and read its main cause.
3. Test the cause before changing the formula, for example KU, pH, air content or gloss.
4. Change one additive at a time, at levels around the product example of its family.
5. Confirm the fix with the test named in the directory row and the tests table.

A single change in paint additive dosage shows which additive moved the result, while 2 changes at once hide it. A ladder of levels around the product example, stepping the dose up and down, shows the working range of the fix; the ladder method is set out under paint additive dosage. The test you confirm with should be the same test that first showed the defect, so the before and after values compare directly.

Regulatory Limits on Common Defect Fixes#

4 common defect fixes carry EU rules: methyl ethyl ketoxime (MEKO) against skinning, octoate driers against wrinkling and loss of dry, 1,2-benzisothiazol-3(2H)-one (BIT) against in-can spoilage, and silicone defoamers against foaming. The table gives the instrument, entry and date of each rule and what it means for the paint.

Note 12 makes the octoate rule a sum rule: the 0.3 % trigger applies to all 2-ethylhexanoates in the paint together, never to each drier assessed separately. Cobalt carboxylates are not substances of very high concern; only cobalt dichloride, sulfate, dinitrate, carbonate and diacetate are on the Candidate List.

MEKO stays legal in paints for professional users, and the restriction targets supply to the general public. VOC limits, biocide approvals, CLP labels and restricted substances for every family are covered under paint additive regulations.

For silicone defoamers, the entry 70 limit applies to residual D4, D5 and D6 with no derogation for decorative paints. US and Indian rules for these fixes sit on the regulation pages, and this index gives no values for them.

Getting Help With a Defect: Formulation Review and Additive Quotes#

A defect that persists after the additive fix in the families table needs a formulation review, and an additive change needs quotes from suppliers of that additive class. A review looks at the whole additive package and at the process side of the defect page, not at one additive alone.

A formulation-help request names the paint type, the defect, the current additive package and the location, and a quote request names the additive family or substance, the grade or performance target, the paint type, the annual volume, the packaging and the delivery country. Sourcing by additive class is explained under paint additive suppliers and manufacturers.

Prices depend on grade, pack size, volume and delivery country, so this site publishes none. The quote form collects exactly these factors, so each supplier answers the same specification.

Which Paint Types Show Which Defects?#

Latex paints show 3 of the directory defects, spatter, viscosity loss and surfactant leaching, and alkyd paints show 2, loss of dry and wrinkling. The latex defects come from the thickener network and the surfactant load of the water phase, and the alkyd defects from the drier package of an oxidatively curing film.

Paint formulations differ by paint type, so the same family carries a different fix in a latex and an alkyd paint. Each additive package is set out in paint formulations by paint type. The 2 paint types with defect links are listed below.

• Latex paints: spatter, viscosity loss, surfactant leaching; see emulsion (latex) paint formulation.
• Alkyd paints: loss of dry, wrinkling; see alkyd paint formulation.