Compared with conventional paints, white basecoats are formulated with high loadings of pigment. Pigment/binder ratios as high as 1.2/1.0 w/w are not uncommon. This is necessary to achieve the required opacity at low film thicknesses of around 8 microns.
(ii) Solvents
Both sheet fed and DWI type end uses rely upon rollercoating as the method of application and both the enamels or lacquers, as well as the resins upon which they are based, contain high boiling point, slow evaporating solvents such as Solvesso® 150 or 100 (Esso Chemicals), Shellsol®AB (Shell Chemicals), Dowanol® PM and PMA (Dow Chemicals). Due to the faster coating speeds and higher oven temperatures in 2 piece can manufacture, very slow solvents are imperative in order to avoid solvent popping and to realise good flow of the enamel.