Paint driers are metal carboxylate catalysts that speed the oxygen-driven cure of alkyd, oil-modified and epoxy ester paints, and formulators choose them from 3 function classes: primary, through and auxiliary driers. A drier, also called a siccative, is dosed as % metal on binder solids, and alkyd gloss paints pair a surface metal such as cobalt with zirconium and calcium. The wrong balance shows up in the film: excess cobalt wrinkles it and shifts its colour, while zinc slows the surface and keeps it smooth.
Driers are one of the 15 families of paint additives, and this page covers how they work, the 3 classes and their metals, 4 alternative systems including cobalt-free and octoate-free driers, selection for 6 paint types, all 8 drier substances with a page on this site, 3 drier defects, the CLP, REACH, Ecolabel and US rules, the ASTM tests and how to source a grade. Two rules frame every choice in the EU: since 2025-02-01 a paint is Repr. 1B when its 2-ethylhexanoates sum to 0.3 % or more, and an EU Ecolabel paint carries at most 0.10 % w/w of driers in total.
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 Driers and Why Do Oxidative Paints Need Them?#
A drier (siccative) is a metal salt of an organic acid, such as a 2-ethylhexanoate (octoate) or neodecanoate of cobalt, manganese, zirconium or calcium, that speeds the oxygen-driven crosslinking of alkyd, oil-modified and epoxy ester paints. The salt is supplied as a solution in a carrier such as white spirit, dearomatized hydrocarbon or xylene, so a drier is specified by its metal, its acid and its metal content.
Three examples show one drier per class. Cobalt octoate (CAS 136-52-7) is a primary drier, zirconium octoate (CAS 22464-99-9) is a through drier and calcium octoate (CAS 136-51-6) is an auxiliary drier. All three are used together in alkyd gloss paints, and the class table below gives one sourced metal level for each.
Driers act in binders that cure by autoxidation, the reaction of the binder with atmospheric oxygen that crosslinks the film. Alkyd, oil-modified and epoxy ester binders cure this way, while two-component polyurethane paints cure by a catalyzed isocyanate-hydroxyl reaction and need a catalyst instead. The binder is the film former among the paint raw materials. Binder, pigment, extender, solvent and the additive package are described under paint raw materials.
Which Drying Stages Do Driers Shorten?#
Driers shorten 3 drying stages that the US AIM rule names for quick-dry enamels and measures by ASTM D1640/D1640M-14(2022): set to touch, tack free and dry hard. The 3 stages and their quick-dry enamel limits under 40 CFR 59.401 are listed below.
- Set to touch: 2 h or less.
- Tack free: 4 h or less.
- Dry hard: 8 h or less.
The 40 CFR 59.401 definition applies to a nonflat coating applied from the container at 16 to 27 °C (60 to 80 °F) with a 60-degree gloss of 70 or more, so the three times describe a fast air-drying enamel, not every alkyd paint. ASTM D1640/D1640M-14(2022) covers drying, curing and film formation of organic coatings; hardness after the dry-hard stage is a separate measurement, by pendulum or pencil, described in the test section below.
How Do Paint Driers Work? Autoxidation in the Film#
Paint driers work by speeding autoxidation: a primary (surface) drier starts the oxygen uptake at the film surface, a through drier carries the cure into the lower film, and an auxiliary drier adjusts the rate of both. Pirs and co-authors (Acta Chimica Slovenica, 2015) followed the autoxidation of a high-solids long oil alkyd resin of 90 % solids by FT-IR spectroscopy. In that study, a strontium through drier combined with a cobalt or an iron bispidon surface drier accelerated the reaction.
Balance between the classes matters because each metal acts at a different depth of the film. Excess cobalt causes wrinkling and a change of color, as the cobalt data sheet in the class table states. Zinc retards surface drying, which prevents wrinkling and orange peel and slightly increases the dry time.
3 Types of Paint Driers Compared#
The 3 types of paint drier are primary (surface) driers, through driers and auxiliary driers, and in the data sheets of the class table alkyd gloss paints combine cobalt or manganese with zirconium and calcium.
The table compares the 3 classes by metals, role in the film, sourced example levels with their basis, strengths and limits.
| Class | Metals | Role in the film | Example level (product, basis, source) | Strengths | Limits |
|---|---|---|---|---|---|
| Primary (surface) driers | Cobalt, manganese, iron, vanadium; cerium as a rare-earth top drier | Start the oxygen uptake at the film surface | Octa-Soligen Cobalt 12 (Borchers TDS): 0.03-0.08 % Co metal on binder solids; Octa-Soligen Manganese 10 (Borchers TDS): 0.01-0.05 % Mn metal on binder solids; Octa-Soligen Iron 7/8 (Borchers TDS): 0.1-1.0 % Fe metal on binder solids, full effect only above 150 °C (302 °F) | Fast surface dry; cerium gives a light color | Excess cobalt wrinkles the film and changes its color; manganese can discolor pale or clear paints; iron needs stoving |
| Through driers | Zirconium, strontium, bismuth; lead (legacy, restricted) | Carry the cure through the lower film | Octa-Soligen Zirconium 18 (Borchers TDS): 0.05-0.30 % Zr metal on binder solids; strontium: see the through driers page | Zirconium gives better color and lower yellowing than other secondary driers | Bismuth octoate's sourced paint role is a polyurethane catalyst; lead driers fall under the lead rules of the regulation section |
| Auxiliary driers | Calcium, zinc, lithium, potassium; barium | Adjust the rate of the primary and through driers | Octa-Soligen Calcium 10 basic (Borchers TDS): 0.03-0.30 % Ca metal on binder solids; Octa-Soligen Zinc 10 (Borchers TDS): 0.03-0.50 % Zn metal on binder solids; Borchers Deca Barium 12.5 (Borchers product page): 0.1-0.5 % Ba metal on binder solids | Zinc prevents wrinkling and orange peel | Zinc slightly increases the dry time |
The class lists follow the class pages of this site: vanadium, lithium and potassium are members without a sourced level here, cerium sits with the surface driers and barium with the auxiliary driers. Each level in the table is one product's data-sheet value, not a range for the whole class.
Which Metals Act at the Surface and Which Through the Film?#
Cobalt, manganese, iron and cerium are the surface metals with sourced product data. Cobalt is combined with zirconium and calcium in alkyd gloss paints. Manganese is used with cobalt in alkyd gloss and pigmented alkyd paints and can discolor pale or clear paints. Iron carboxylate serves stoving, dark baking finishes and anticorrosion primers, because it reaches its full effect only at stoving temperatures. Cerium is a rare-earth top drier with a light color.
Zirconium, strontium and bismuth make up the through class beside legacy lead. Zirconium drier works with cobalt or manganese and calcium in alkyd gloss paints and gives better color and lower yellowing than other secondary driers. Strontium carried the autoxidation of the high-solids alkyd in the 2015 FT-IR study together with cobalt or iron surface driers. Bismuth is listed in the through class, and its sourced role in liquid paint is described under selection by paint type below.
Calcium, zinc and barium are the auxiliary metals with sourced product levels. Calcium drier is used in alkyd gloss and epoxy ester paints, both in solventborne alkyd primers and in epoxy ester primers of the selection table. Zinc is the anti-wrinkling metal of the class, and barium has one product level in the class table.
Which Carboxylic Acids Carry the Metal?#
Paint drier metals are carried by 3 acid types: 2-ethylhexanoic acid in the octoates, neodecanoic acid, and natural acids in salts such as cobalt naphthenate, cobalt tallate and lead naphthenate. Product lines follow the acid: the Hex-Cem line is based on 2-ethylhexanoate, the Ten-Cem line on neodecanoate, and 10 % Cobalt Hydro-Cure IV on neodecanoic acid salts for waterborne paints only. Octoate-free driers replace 2-ethylhexanoic acid with neodecanoic, isononanoic, ricinoleic or other acids, and they are not drop-in replacements, because the longer acid chains lower the metal concentration and change the viscosity.
The acid also decides the CLP entry. Every 2-ethylhexanoate salt, including iron 2-ethylhexanoate (CAS 19583-54-1, EC 243-169-8), falls under the group entry 607-230-00-6 described in the regulation section, while cobalt neodecanoate stays outside it. Natural-acid salts carry their own lines: cobalt naphthenate (CAS 61789-51-3, EC 263-064-0) has no Annex VI entry, and its REACH joint submission notifies STOT RE 1 H372, Skin Sens. 1 H317 and Aquatic Chronic 3 H412. Cobalt tallate (CAS 61789-52-4, EC 263-065-6) has no Annex VI entry and a majority notification of H302, H317 and H411, and lead naphthenate (CAS 61790-14-5) is covered by the lead compounds entry 082-001-00-6 only.
Which Alternative Drier Systems Exist Beyond the 3 Classes?#
Four drier systems sit beside the 3 classes: cobalt-free catalysts based on iron or manganese, octoate-free driers on neodecanoic or other acids, driers for waterborne alkyds, and japan drier.
The table lists each system with what it replaces, sourced product examples and the point to watch.
| System | What it replaces | Example (product, level, basis, source) | Watch-out |
|---|---|---|---|
| Cobalt-free driers | Cobalt | Borchi OXY-Coat (Borchers product page), iron complex in 1,2-propylene glycol: 0.5-3 % product as supplied on resin solids (ladder study); Borchers Dry 0411 HS (Borchers product page), 6.85-7.25 % Mn with an organic accelerator: 0.1-0.5 % product on binder solids; Umicore ECOS polymer-bound driers, including a cobalt-free manganese polymer grade | Too much OXY-Coat may inhibit through-dry (Borchers product page) |
| Octoate-free driers | 2-Ethylhexanoic acid | Borchers Deca Zirconium 12 (Borchers product page), based on neodecanoic acid salts: 0.05-0.30 % Zr metal on resin solids | Not drop-in: lower metal concentration and different viscosity (Umicore octoate-replacement page) |
| Driers for waterborne alkyds | Solvent-carried grades | 10 % Cobalt Hydro-Cure IV (Borchers TDS): 0.03-0.08 % Co metal on vehicle solids; Octa-Soligen Zirconium 10 Aqua (Borchers product page): 0.05-0.30 % Zr metal on binder solids; Borchi OXY-Coat 1101 (Borchers product page): 0.25-2 % product on resin solids | Dri-Rx-HF (Borchers product page, 29-31 % bipyridyl): 0.2-0.5 % on vehicle solids in water-based paints protects cobalt against hydrolysis |
| Japan drier | See the japan drier page | See the japan drier page | See the japan drier page |
Cobalt-free catalysts need their own dosage: overdosing the iron complex may inhibit through-dry, and an excess of the high-solids manganese catalyst in the selection table could reverse the dry. Polymer-bound driers take a different route and incorporate the metal in a polymer to limit its bio-accessibility. Octoate-free grades answer the EU classification of 2-ethylhexanoic acid and its salts as Repr. 1B, set out in the regulation section. The name japan drier should not be confused with the SCAQMD Rule 1113 category "Japans", a faux finishing category of concentrated pigments ground in a slow-drying vehicle.
How to Choose Driers by Paint Type#
Choose the drier package by binder and cure conditions first: cobalt with zirconium and calcium for solventborne alkyd gloss paints, iron or manganese catalysts where cobalt must go, water-dispersible grades for waterborne alkyds, and iron for stoving finishes.
The table matches 6 paint types to a drier package, a sourced example with its basis and the point to watch.
| Paint type | Drier package | Example (product or guide formulation, basis, source) | Watch-out |
|---|---|---|---|
| Alkyd paint formulation: solventborne alkyd gloss | Co + Zr + Ca | Borchers CTT 2022 control alkyd: 12 % Co drier 0.15, 5 % Ca drier 0.38, 12 % Zr drier 0.54 parts per 100 parts base paint; 12% Cobalt Ten-Cem (Borchers product page): 0.03-0.08 % Co metal on vehicle solids in conventional alkyds | Wrinkling at excess cobalt |
| High-solids long oil alkyd | Mn catalyst, Fe complex, accelerator | Borchi Dragon (Borchers product page): 0.5-3 % product on resin solids; Dri-Rx-HF (Borchers product page): 0.2 % on vehicle solids in high solids | Excess Borchi Dragon could reverse the dry; Hein advised avoiding Co with Ca in high solids (as reported by Pirs et al. 2015) |
| Water-based enamel paint formulation: waterborne alkyd enamel | Water-dispersible Co, Mn, Zr | 5 % Manganese Hydro-Cure (Borchers product page): 0.01-0.05 % Mn metal on vehicle solids; Octa-Soligen Zirconium 10 Aqua: 0.05-0.30 % Zr metal on binder solids | Hydrolysis of cobalt (Dri-Rx-HF protects it) |
| Primer formulation: solventborne alkyd anticorrosive primer | Ca premix + combination drier | Heubach guide formulation 299-03: Octa-Soligen Calcium 10 basic 0.10 (premix), Octa-Soligen 173 1.20 (let-down), parts by weight per 100; PVC 38.4 % | Anti-skinning agent added separately while stirring |
| Epoxy paint formulation: epoxy ester primer | Ca + Co | Heubach epoxy ester primer guide formulation 734-04: Ca drier 0.25 (premix) + 0.35 (let-down), Octa-Soligen Cobalt 6 0.20, parts by weight per 100 | Calcium split between premix and let-down |
| Stoving (baking) enamel | Fe | Octa-Soligen Iron 7/8 (Borchers TDS): 0.1-1.0 % Fe metal on binder solids | Full effect only above 150 °C (302 °F) |
Climate narrows the choice further. High atmospheric humidity severely inhibits manganese, and cerium is recommended over zirconium at high humidity, low temperature or both, so humid or cold application conditions shift the package. Each paint type's full additive package, with the drier package as one line of it, is set out in paint formulations by paint type.
Two-component polyurethane paints cure by the catalyzed isocyanate-hydroxyl reaction, not by autoxidation, so they take a catalyst instead of a drier package. Bismuth octoate serves there as a tin-free catalyst of that reaction in 1K and 2K solventborne polyurethane paints, at the product level shown in the substance table.
What Is a Combination Drier?#
A combination drier is a single drier product that supplies more than one drier metal, so one addition delivers several metals to the let-down. In the solventborne alkyd anticorrosive primer guide formulation of the selection table, Octa-Soligen 173 is that combination drier at 1.20 parts by weight in the let-down, after 0.10 parts of a basic calcium drier in the premix.
The same guide formulation adds its anti-skinning agent separately while stirring and has a pigment volume concentration of 38.4 %. A guide formulation states parts by weight of the product, not % metal on binder solids, so converting it to a metal level needs the metal content of the product and the binder solids of the paint.
Which Metal Ratios Do Published Alkyd Formulations Use?#
The control alkyd of a 2022 ladder study uses a zirconium-to-cobalt metal ratio of about 3.6 to 1 and a calcium-to-cobalt ratio of about 1.1 to 1. Its drier package, listed in the selection table, is 0.15 parts 12 % cobalt drier, 0.38 parts 5 % calcium drier and 0.54 parts 12 % zirconium drier per 100 parts base paint. Calculated from the drier strengths, that is 0.018 parts cobalt, 0.019 parts calcium and 0.065 parts zirconium metal per 100 parts base paint (ratios calculated as 0.065 / 0.018 and 0.019 / 0.018).
Pirs and co-authors (2015) dosed an 18 % strontium drier at 1:1, 1:3.5 and 1:10 to the surface drier, a 10 % cobalt drier at 1 wt % on resin solids or an iron drier at 0.78 wt %, and found the lowest ion diffusivity at the 1:1 ratio; these are study levels, not a recommendation. The same paper reports that Hein advised avoiding cobalt with calcium in high-solids alkyds, because calcium promotes cobalt activity and premature top-drying. The epoxy ester primer of the selection table splits its calcium drier between premix and let-down and adds a 6 % cobalt drier.
Complete Table of Paint Drier Substances#
The table lists all 8 drier substances with a page on this site, with CAS number, class, function in paint, an example level with its basis and source, and the CLP hazard line.
| Substance | CAS | Class | Function in paint | Example level (product, basis, source) | CLP hazard line |
|---|---|---|---|---|---|
| Cobalt octoate (cobalt 2-ethylhexanoate) | 136-52-7 | Primary | Surface drier, combined with zirconium and calcium in alkyd gloss | Octa-Soligen Cobalt 12 (Borchers TDS): 0.03-0.08 % Co metal on binder solids | Harmonized CLP Annex VI index 607-230-00-6 (group entry "2-ethylhexanoic acid and its salts"): Repr. 1B H360D; Danger (ATP18, Delegated Reg. (EU) 2022/692, applicable since 2023-11-23; Notes A, X, 12 added by ATP20, Delegated Reg. (EU) 2023/1435, applicable since 2025-02-01) |
| Manganese octoate | 15956-58-8 | Primary | Surface drier and cobalt replacement metal, used with cobalt | Octa-Soligen Manganese 10 (Borchers TDS): 0.01-0.05 % Mn metal on binder solids | Annex VI 607-230-00-6: Repr. 1B H360D; Danger (ATP18, since 2023-11-23; Notes A, X, 12 by ATP20, since 2025-02-01) |
| Zirconium octoate | 22464-99-9 | Through | Through drier with cobalt or manganese and calcium; low yellowing | Octa-Soligen Zirconium 18 (Borchers TDS): 0.05-0.30 % Zr metal on binder solids | Annex VI 607-230-00-6: Repr. 1B H360D; Danger (ATP18, since 2023-11-23; Notes A, X, 12 by ATP20, since 2025-02-01) |
| Strontium octoate | 2457-02-5 | Through | Through drier; accelerated autoxidation with cobalt or iron surface driers (Pirs et al. 2015) | See the strontium octoate page | Annex VI 607-230-00-6: Repr. 1B H360D; Danger (ATP18, since 2023-11-23; Notes A, X, 12 by ATP20, since 2025-02-01) |
| Bismuth octoate | 67874-71-9 | Through | Tin-free isocyanate-hydroxyl catalyst in polyurethane paints | Borchi Kat 24 (Borchers product page), 23-25 % Bi: 0.01-0.12 % product on total solid binder | Annex VI 607-230-00-6: Repr. 1B H360D; Danger (ATP18, since 2023-11-23; Notes A, X, 12 by ATP20, since 2025-02-01) |
| Lead octoate and lead driers | 301-08-6; lead naphthenate 61790-14-5 | Through (legacy) | Legacy through drier; replacement guidance only | Legacy: alternatives are zirconium, strontium and calcium driers | Annex VI 082-001-00-6 (lead compounds): Repr. 1A H360Df, Acute Tox. 4* H332, Acute Tox. 4* H302, STOT RE 2* H373**, Aquatic Acute 1 H400, Aquatic Chronic 1 H410 (Danger); lead 2-ethylhexanoate is also covered by 607-230-00-6 (Repr. 1B H360D) |
| Calcium octoate | 136-51-6 | Auxiliary | Auxiliary drier in alkyd gloss and epoxy ester paints | Octa-Soligen Calcium 10 basic (Borchers TDS): 0.03-0.30 % Ca metal on binder solids | Annex VI 607-230-00-6: Repr. 1B H360D; Danger (ATP18, since 2023-11-23; Notes A, X, 12 by ATP20, since 2025-02-01) |
| Zinc octoate | 136-53-8 | Auxiliary | Retards surface drying against wrinkling and orange peel | Octa-Soligen Zinc 10 (Borchers TDS): 0.03-0.50 % Zn metal on binder solids | Annex VI 607-230-00-6: Repr. 1B H360D; Danger (ATP18, since 2023-11-23; Notes A, X, 12 by ATP20, since 2025-02-01) |
| All other paint additive substances |
Four further drier salts are sections of the class and system pages rather than pages of their own: cobalt neodecanoate on the octoate-free page, and cobalt naphthenate, cobalt tallate and iron 2-ethylhexanoate on the primary driers page.
Which Paint Defects Do Driers Cause or Prevent?#
Drier choice decides 3 paint defects that have pages of their own: wrinkling, yellowing and loss of dry, each with a drier cause and a drier fix.
The table links each defect to its drier cause and its drier fix.
| Defect | Drier cause | Drier fix |
|---|---|---|
| Paint wrinkling | Excess cobalt; cobalt with calcium in high-solids alkyds promotes premature top-drying (Hein, as reported by Pirs et al. 2015) | Zinc drier, which retards surface drying |
| Paint yellowing | Manganese can discolor pale or clear paints | Zirconium drier, with better color and lower yellowing than other secondary driers |
| Loss of dry in alkyd paint | See the loss of dry page | See the loss of dry page |
Cobalt-free catalysts add a dosage risk of their own: overdosing the iron complex may inhibit through-dry, and an excess of the high-solids manganese catalyst could reverse the dry, so a cobalt-free package is set by a ladder of levels.
Drier defects show up in the drying film, as the table shows. All other defects and their additive fixes are collected under paint defects.
How Are Paint Driers Regulated? CLP, REACH and US Rules#
Every octoate drier falls under one harmonized CLP group entry, Annex VI index 607-230-00-6 for 2-ethylhexanoic acid and its salts, classified Repr. 1B H360D (Danger) by ATP18, Delegated Regulation (EU) 2022/692, applicable since 2023-11-23. ATP20 (Delegated Regulation (EU) 2023/1435, applicable since 2025-02-01) added Notes A, X and 12, and under Note 12 a paint is Repr. 1B when the sum of all 2-ethylhexanoates plus free acid is 0.3 % or more; the entry sets no specific concentration limit. REACH Annex XVII entry 30 lists the same salts in Appendix 6 by Commission Regulation (EU) 2023/1132, applicable since 2023-12-01, so an octoate drier or a paint with an individual octoate concentration of 0.3 % or more is not supplied to the general public and is packed "Restricted to professional users"; professional supply stays legal.
The table lists the instruments that reach paint driers, with their dates.
| Instrument and date | What it requires | Driers affected |
|---|---|---|
| CLP labeling of paints: Annex VI 607-230-00-6, ATP18 (Delegated Reg. (EU) 2022/692), since 2023-11-23; Note 12 by ATP20 (Delegated Reg. (EU) 2023/1435), since 2025-02-01 | Repr. 1B H360D for the acid and its salts; a paint is Repr. 1B when the sum of all 2-ethylhexanoates plus free acid is 0.3 % or more | Cobalt, manganese, zirconium, strontium, bismuth, calcium, zinc, iron and lead 2-ethylhexanoates |
| Restricted and banned substances in paint: REACH Annex XVII entry 30, Appendix 6, Commission Reg. (EU) 2023/1132, since 2023-12-01 | No supply to the general public at an individual concentration of 0.3 % or more; packaging marked "Restricted to professional users" | Octoate driers (restricted for consumers, not banned in paint) |
| REACH Candidate List; Directive (EU) 2026/2450 of 2026-10-21 (OEL) | Candidate List: cobalt dichloride (2008-10-28), cobalt sulfate, dinitrate, carbonate and diacetate (2010-12-15); OEL for "cobalt and inorganic cobalt compounds" | Cobalt carboxylates are neither listed nor named |
| Lead in paint: CLP 082-001-00-6 (CLP00, since 2010-12-01); Annex XVII entry 30, Appendix 5; 16 CFR 1303 (since 2009-08-14) | Repr. 1A H360Df with specific limits Repr. 2 H361f at 2.5 % or more and STOT RE 2 H373 at 0.5 % or more (as lead); no supply to the general public; US limit 0.009 % (90 ppm) of the nonvolatile content or dried film | Lead octoate and lead naphthenate (legacy) |
| EU Ecolabel for paints: Decision (EU) 2025/2607, valid until 2032-12-31 | Driers classified CMR excluded (criterion 4.3(a)); total driers 0.10 % w/w or less in the final product; H400/H410 derogation only for cobalt driers up to 0.050 % w/w; derogated drier hazards H301, H317, H373, H412, H413 | Octoate driers excluded as Repr. 1B |
| VOC in paint: Directive 2004/42/EC Art. 2(5); 40 CFR 59.406 | EU: organic compound with an initial boiling point of 250 °C (482 °F) or less at 101.3 kPa; US AIM: g/L less water and exempt compounds | Drier carriers (white spirit, dearomatized D40 or D60 hydrocarbon, xylene) count; the carboxylate is non-volatile |
| US TSCA and California Proposition 65 | Inventory listing; Prop 65 warning for listed chemicals | TSCA: the 7 non-lead octoate CAS numbers of the substance table, 2024 CDR active (EPA SRS, 2026-11-03); Prop 65: lead via "Lead and lead compounds" (cancer, 1992-10-01) and "Lead" (developmental, female and male reproductive toxicity, 1987-02-27) |
Cobalt neodecanoate (CAS 27253-31-2) has no Annex VI entry, and its REACH joint submission (30.04 % of notifiers) notifies Acute Tox. 4 H302, STOT RE 1 H372, Skin Sens. 1 H317 and Aquatic Chronic 3 H412; see the product SDS. No cobalt carboxylate is on the REACH Candidate List. The EU binding occupational exposure limit of Directive (EU) 2026/2450 for "cobalt and inorganic cobalt compounds" is 0.01 mg/m3 inhalable and 0.0025 mg/m3 respirable (as cobalt), with transitional values of 0.02 and 0.0042 mg/m3 until 2032-11-20 and transposition by 2028-11-20, and the entry does not name cobalt carboxylates.
The EU Ecolabel for paints, Decision (EU) 2025/2607, repeals Decision 2014/312/EU and excludes driers classified CMR, so no octoate drier enters an Ecolabel paint; the derogation for cobalt driers up to 0.050 % w/w can apply only to a cobalt drier that is not CMR. These drier rules are one part of the paint additive regulations of the EU and the US. VOC, biocide, CLP label and restricted-substance rules for every family are on paint additive regulations.
US rules reach driers through lead and VOC. 16 CFR 1303 bans consumer paint with more than 0.009 % (90 ppm) lead of the nonvolatile content or dried film since 2009-08-14, down from 0.06 %, and paints for motor vehicles and boats are outside its scope. Drier carriers count in US AIM VOC, calculated in g/L less water and exempt compounds (40 CFR 59.406), and SCAQMD Rule 1113 has no drier category.
How Is Drier Performance Tested? Drying Time, Hardness and Metal Content#
Drier performance is measured with 3 test groups: drying time by ASTM D1640/D1640M-14(2022), film hardness by pendulum (ASTM D4366-16(2021)) or pencil (ASTM D3363-22), and metal content of the drier solution by ASTM EDTA and oxidimetric methods.
The table assigns each test its current ASTM designation and what it shows for driers.
| Test | Standard and edition | What it shows for driers |
|---|---|---|
| Drying stages | ASTM D1640/D1640M-14(2022) | Set-to-touch, tack-free and dry-hard times of the film |
| Pendulum hardness | ASTM D4366-16(2021) | Hardness development of the cured film |
| Pencil hardness | ASTM D3363-22 | Film hardness by pencil test |
| Metal content of the drier solution | ASTM D2613-01(2023) (calcium or zinc, EDTA); D3804-02(2021) (iron, EDTA); D3969-01(2025) (zirconium, EDTA); D3970-05(2023) (cerium, oxidimetric); D3988-05(2023) (vanadium, EDTA) | Actual metal strength of the drier as delivered |
| Color of the drier solution | ASTM D1544-04(2023) | Gardner color of a transparent liquid |
Three EDTA methods for cobalt (D2373), lead (D2374) and manganese (D2375) in paint driers were withdrawn in 2016 without replacement, and ASTM D600, the specification for liquid paint driers, was withdrawn in 2021 without replacement, so none of them is a current method. Every other paint test method is described under paint test methods.
The metal methods check the stated metal strength of a drier solution, which is the input of every metal-on-binder-solids calculation.
Sourcing Paint Driers: Metal Strength, Carrier and Quote Requests#
Paint driers are bought as solutions of a stated metal strength, and a request names the metal, the acid (octoate or neodecanoate), the carrier, the paint type, the annual volume, the packaging and the delivery country.
The table gives the metal content of 5 drier solutions, each from its product data sheet.
| Product (producer, data sheet) | Metal | Metal content |
|---|---|---|
| Octa-Soligen Cobalt 12 (Borchers TDS) | Cobalt | 11.7-12.3 % Co |
| Octa-Soligen Manganese 10 (Borchers TDS) | Manganese | 9.8-10.2 % Mn |
| Octa-Soligen Zirconium 18 (Borchers TDS) | Zirconium | 17.7-18.3 % Zr |
| Octa-Soligen Calcium 10 basic (Borchers TDS) | Calcium | 9.8-10.2 % Ca |
| Octa-Soligen Zinc 10 (Borchers TDS) | Zinc | 9.8-10.2 % Zn |
Annual volume follows from the metal level. Worked example: 15,000 kg of paint at 40 % binder solids holds 6,000 kg of binder solids, a target of 0.06 % cobalt metal on binder solids needs 6,000 x 0.0006 = 3.6 kg cobalt, and a 12 % cobalt drier supplies it in 3.6 / 0.12 = 30 kg (calculated). US imports of prepared driers fall under HTS 3211.00.00.00, with a general duty of 3.7 % and a column 2 duty of 25 % (USITC, read 2026-11-03; Chapter 99 additional duties not included).
US suppliers deliver an English safety data sheet of 16 sections with the initial shipment and after an update (29 CFR 1910.1200(g)). Lead driers get no quote request on this site, because they are legacy substances; the lead octoate page gives their replacement. Sourcing and qualifying producers and distributors is covered on paint additive suppliers and manufacturers.
Three related pages cover the calculation, regional sourcing and the market.
- Drier dose from metal strength and binder solids: paint drier calculator
- Producers and distributors in India: paint additive manufacturers in India
- Market size, segments and leading producers: paint additives market
How Driers Interact With Other Additive Families#
Driers interact with 3 other paint additive families: anti-skinning agents, whose effect depends on the drier metal, catalysts that cure non-oxidative binders, and light stabilizers, whose blends can shift tack-free time. The 3 interactions are listed below.
- Anti-skins: volatile oxime anti-skins are especially effective with cobalt and not efficient with cobalt replacements, and non-volatile antioxidant anti-skins are recommended in cobalt-replacement strategies; see anti-skinning agents.
- Catalysts: polyurethane paints cure by the isocyanate-hydroxyl reaction, which bismuth octoate and other catalysts speed in place of a drier; see catalysts for polyurethane paints.
- Light stabilizers: a producer claims a shorter tack-free time in alkyd paints for its newer UVA/HALS blend, Tinuvin 5071, than for its older blend; see UV absorbers and light stabilizers for paint.
How Much Drier Does an Alkyd Paint Contain?#
Drier levels in an alkyd paint depend on the metal and the product: the cobalt, zirconium and calcium products of the class table give 0.03-0.08 % cobalt, 0.05-0.30 % zirconium and 0.03-0.30 % calcium metal on binder solids.
No single class-wide drier level is given on this page, because each value belongs to one product. The drier mass follows from batch mass times binder-solids fraction times target % metal, divided by the % metal of the drier solution. Ladder studies that start from such a level and step it up and down are explained under paint additive dosage.