How to Read a Paint Drier Specification: Metal Content, Viscosity and Drying Performance
September 3, 2026 · Technical
The COA Is the Specification
Paint driers are metal soaps — the active ingredient is the metal content, not the product name. A 'cobalt drier' from two suppliers at 6% and 10% Co are different products, and comparing them by name alone is the most common dosing error in alkyd formulation.
Five Parameters to Check
| Parameter | What It Tells You | Typical Value (our Cobalt Octoate) |
|---|---|---|
| Metal content | Effective strength per kg; drives dose calculation | 8.0 ± 0.2% Co |
| Solvent carrier | Compatibility and VOC contribution | 200# solvent oil (mineral spirits) |
| Viscosity | Pumping, dosing accuracy, sedimentation tendency | 150–250 mPa·s @ 25 °C |
| Flash point | Transport and warehouse classification | ≥ 40 °C (closed cup) |
| Acid value | Free acid balance; very high values can affect resin stability | ≤ 15 mg KOH/g |
Standardizing Dosing Across Suppliers
Express the dose as metal on resin solids, not as product weight. Example: 0.1% Co on resin solids with an 8% Co drier equals 1.25% product on resin — while a 10% Co drier needs only 1.0%. Our data sheets give both, so switching sources does not change your paint.
Composite Drier Practice
Fast surface dry (cobalt octoate or cobalt naphthenate) plus a secondary through-dry system — zirconium octoate and cerium octoate for non-yellowing systems, manganese octoate or lead naphthenate where regulations allow — is the standard route to balanced film properties without cobalt over-dosing.
Verification Before Bulk Orders
Order a 1 kg sample, measure metal content by titration or AAS, and run a standard drying-time test on your own resin. Compare against the COA before approving the batch — see our quality checks guide. Third-party analysis (SGS/Intertek) is available on request for any order.