Acts as a drier for oil colours and mediums.

Cobalt driers made from cobalt octoate or cobalt naphtenate are the only recommended siccatives for artists oil colours and mediums as their addition in the correct proportion has a minimal effect regarding darkening and embrittlement of the paint film.

Constituents

Cobalt Octoate, White Spirit.

Product Application

Cobalt driers may be added to oil and alkyd colours, oil mediums and drying oils in recommended measured quantities.

Cobalt driers are known as ‘surface’ siccatives (driers) and will only speed the drying of the surface of the paint film. They are not ‘through-film’ siccatives and do not perform as successfully with thick films of oil (i.e. impasto technique)

Langridge recommends that Cobalt Driers should be added to an oil medium or artists’ drying oil rather than mixed directly into the oil paint. Measuring quantities of driers directly into small amounts of colour is difficult and prone to miscalculation.

Langridge recommends addition to mediums and oils to reduce the likelihood of over use and to simplify the artists’ studio practice. Once mixed with an oil or medium, the artist can dispense with concerns about constant ongoing additions of driers.

Add Cobalt Driers as an approximate 1% addition. (i.e. To 500ml of Linseed Oil add 5ml of Cobalt Drier.)

Shake or stir well together.  When initially mixed together, the driers will impart a blue/green cast to the oil or medium with which it is mixed. Exposed to indirect sunlight for a few days will remove this colour difference (Exposing the oil or medium to indirect sunlight will not sun bleach or thicken the material).

If used in correct proportions, the colour of the cobalt drier will not interfere with oil paints’ brightness or colour saturation.

Driers made from lead, manganese and other proprietorial mixtures that do not wholly contain cobalt driers are to be avoided as they promote darkening and loss of flexibility. However, even Langridge Cobalt Driers are to be used sparingly as its over-use will destroy paint films. 

Additional Product Information

Problems with ambient temperature and humidity

Because artists drying oils (oils that dry to a hard, non-reversible film) absorb oxygen to harden, so the ambient temperature and humidity have an effect on the speed and success of film hardening.

Oils, oil paints and oil mediums should not be applied in temperatures below 10o F or above 40o F.

Relative humidity level should not exceed 50%. Moisture in a high humidity environment will create a fine layer of water on top of the paint film preventing oxygen from being absorbed. This will dramatically slow the hardening of the oil, potentially weakening the paint film even when fully dry.

Temperature and relative humidity can be controlled in the artists studio with heating/cooling devices and the use of dehumidifying devices.

Accelerating the drying rate of a completed painting

Cobalt Driers should not be applied to a painting to accelerate the drying of an already laid paint film.

If a painting is taking longer to dry than is expected, it is recommended to place the artwork in a dry, warm, dust-free area with a steady airflow across the surface.

Once paint has been applied to a painting no attempt should be made to add driers or rapid drying

mediums on top to accelerate drying. This can lead to cracking and potential flaking of the paint film.

Accelerating the drying rate of varnishes

Cobalt Driers cannot speed the drying of artists’ varnishes as they contain no oil. Artists’ varnishes dry by evaporation of the solvent. If a varnish remains tacky for longer than is recommended by the manufacturer, this may be due to latent solvent trapped in the preceding paint film. As it attempts to evaporate through the surface it will solubilize the resin of the varnish. Place the artwork in a dry, warm, dust-free area with a steady airflow across the surface.

Thinning

For best results thin with Distilled Gum Turpentine. However, Langridge Low Toxic Solvent may be substituted. 

Appearance

Langridge Cobalt Driers is a dark blue colour liquid with characteristic White Spirit odour.

Clean Up

Clean measuring containers with Artists White Spirit. Langridge Low Toxic Solvent may be substituted.

For further washing apply a small quantity of Marseille or other pure olive oil soap to release any remaining colour. Wash thoroughly in warm water. Leave to fully dry before using for oil colours.