PLGN 1.08 Special process colours
When any colour is to be used on rough surfaces, or where a marked change of colour is to be made, an amended process may be required and the finishing system for that surface amended to include the additional coats necessary.
The finishing system for a surface that is to be significantly lighter than the previous colour (e.g. from Black to White) may also need to be amended to include the application of further coats of finish or the use of different colours or products as undercoats prior to finishing.
Some strong colours, such as Poppy and Monarch in the revised BS4800 range, cannot be made with the same hiding power as ordinary colours if they are to have satisfactory durability and purity of colour and therefore may require extra coats to be applied to achieve full opacity.
These strong colours, known as 'Special Process Colours' are identified as such in colour cards from the supplying stockists or the Trade Technical Advice Centre (see below) with specific instruction on how many coats to apply to achieve full opacity. Some of this information will also be given on the can labels. This may involve the application of further coats of finish or the use of different colours or products as undercoats prior to finishing.
Refer to BS 6150: 2006 Code of Practice for Painting of Buildings Appendix B: Paint Colours (or as amended). See relevant colour card for further guidance.
Colour Guidance
- NCS: All colours with a colour intensity of 60 or more. e.g. (1060-Y10R).
- Colour Palette: BB, RB, BG colours with chroma value >350.
- Colour Palette: YY, YR, GY colours with chroma value >450.
- Colour Palette: RR, GG colours with chroma value >400 e.g. 45YY 71/664.
This is not an exclusive list. Contact the Trade Technical Advice Centre to confirm colour requirements.
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