ARTISTS' OIL COLOUR PRUSSIAN BLUE
Colour Index Name: Each pigment can be universally
identified by its Colour Index Generic Name. For example, Cobalt Blue is
Pigment Blue 28, abbreviated to PB28.
Series: The Series number indicates the relative price of
the colour and is determined mainly by the pigment cost. Series 1 is the least
expensive, and Series 5 is the costliest. Where there is no series column, this
indicates the price is uniform across the range.
T/O—Transparency/Opacity: Transparent colours are marked ‘T'
and semi-transparent ‘ST. Opaque colours are marked ‘O' and Semi-Opaque ‘SO';
however, transparency is relative, and the ratings are only provided as a
guide. In addition, any thin film of colour will appear more transparent than a
thicker one.
Permanence: The permanence of an artist's colour is defined
as ‘its durability when laid with a brush on paper or canvas, graded
appropriately and displayed under a glass frame in a dry room freely exposed to
ordinary daylight and an ordinary town atmosphere. In simpler terms, they resist change when exposed to light
and the atmosphere.
- AA - Extremely Permanent
- A - Permanent
- B - Moderately Durable
- C - Fugitive
- For further information on some colours, the rating may
include one or more of the following additions:
- (i) A rated in full strength may fade in thin washes
- (ii) Cannot be relied upon to withstand damp
- (iii) Bleached by acids, acidic atmospheres
- (iv) Fluctuating colour; fades in light, recovers in dark
- (v) Should not be prepared in pale tints with Flake White,
as these will fade
- (vi) A rated with a coating of fixative
Lightfastness: Lightfastness is shown with an ASTM rating
for the pigment. The ASTM abbreviation stands for the American Society for
Testing and Materials. This organization has set standards for the performance
of art materials, including a colour's lightfastness. It has the highest
lightfastness available in this system, and V is the lowest, though ratings I
and II are considered permanent for artists' use.
Where no ASTM rating is given for a Winsor and Newton
colour, it is labelled as N/L, meaning "Not Listed," this usually
indicates that the ASTM has not yet tested the pigment or the type of range. It
does not necessarily imply a lack of lightfastness.
In these cases, we recommend referring to the Winsor and
Newton permanence rating, which evaluates colour on many aspects, including
lightfastness, and indicates a colour's ability to resist fading.
