Although mill additions make up only a minor part of enamel formulations, they have an important effect on the properties both before and after firing.
Mill additions for enamels can be classified into four groups :
Below an overview of typical mill additions to porcelain / vitreous enamels and their function(s)
| Milling Addition | Function |
| Aerosil | for set-up |
| Aluminium oxide | matting agent and to increase heat resistance of ground coat |
| Aluminium hydroxide | equivalent to aluminium oxide |
| Aluminium powder | increase heat resistance in ground coat |
| Antimony trioxide | increase adherence of ground coat |
| Barium chloride | for set-up in cover coat |
| Barium carbonate | for set-up in cover coat |
| Bentonite | for set-up |
| Borax | for set-up in ground coat |
| Boric acid | for set-up |
| Cadmium oxide | to stabilise Cd-Se red enamels |
| Clay | provide bubble structure |
| Cupric chloride | for self lustre enamel 1118 |
| EK-1000 | for continuous clean enamel |
| Feldspar | for ground coat |
| Gumst | increase filmstrength |
| Magnesium chloride | for set-up cover coat |
| Magnesium nitrate | to increase suspension and to prevent fishscales |
| Opacifier UV | opacifier |
| Potash | for set-up |
| Potassium choride | for set-up cover coat |
| Potassium nitrate | oxidizing agent for aluminium enamels |
| Quartz | to increase firing range and matting agent |
| Silicic acid | for set-up |
| Silver sand | for heat resistant ground coat |
| Soda ash | for set-up in ground coat |
| Sodium aluminate | for set-up in cover coat |
| Sodium nitrite | for set-up in ground coat |
| Sodium pyrophosphate | to decrease set-up |
| Sodium silico fluoride | for set-up cover coat |
| Tinoxide | opacifier |
| Titanium dioxide | opacifier |
| Trisodium phosphate | to prevent rusting in cast iron ground coat |
| Urea | to prevent hairlines in cover coat |
| Zirconite | opacifier |
| Zircon oxide | opacifier |