Cranfield (Spectrum) Linseed Oil Paste

From the Cranfield website:

An almost transparent painting medium based on refined linseed oil and alumina. It is similar in consistency to Studio Oil Colours in tubes. It does not promote quick drying and may be used to extend oil colours. It can be used in large ratios where the desired effect is to increase yellowing and darkening of pale colours. It will not increase gloss.