COBALT SICCATIVE

Cobalt Drier

Among all drying additives available to the oil painter, cobalt drier is the most potent and the most widely used in professional studio practice. A surface siccative based on cobalt octoate dissolved in mineral spirits, it accelerates the oxidative drying process of oil paint by catalysing the absorption of oxygen at the surface of the paint film, dramatically reducing drying time even in small quantities.

The SCHAAL Cobalt Drier can be added directly to oils, mediums, or paint on the palette, giving the artist precise control over working and drying time at every stage of a painting.

Key properties

• Powerful surface drier — significantly accelerates drying time of oil colors and mediums
• Based on cobalt octoate : the only siccative recommended for fine art use, with minimal impact on the long-term flexibility and colour of the paint film
• Compatible with all drying oils, oil mediums, and professional oil colors
• Does not significantly alter color saturation or transparency when used in correct proportions
• Ideal for thin to medium paint layers and for artists working in successive sessions
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How to use Cobalt drier is a surface siccative — it accelerates drying at the surface of the paint film, not through its full depth. It is therefore best suited to thin and medium layers. For thick impasto work, it is less effective and can cause surface wrinkling while the underlying paint remains wet.

The recommended addition rate is 1% to 5% by volume, approximately 2 to 3 drops per walnut-sized amount of paint or medium. For larger quantities, add approximately 5ml of cobalt drier per 500ml of oil or medium, shake well, and use the prepared mixture as needed.

Critical warning Cobalt drier is immensely powerful and must never be overused. Excessive amounts cause the surface of the paint film to dry too rapidly, trapping wet paint underneath — leading to wrinkling, cracking, and long-term paint film failure. Measure carefully, always err on the side of less, and never add it directly to light or white colours without testing first, as it may impart a faint blue-green cast. Work in a well-ventilated space and avoid prolonged skin contact.

To simplify your studio practice, consider pre-mixing cobalt drier directly into our Linseed Oil or Painting Medium at the recommended 1% ratio, rather than adding it to each colour individually. For fast-drying impasto work with added body, explore our Medium Gel, which already incorporates cobalt drier in a balanced formula.