The finest marble dust for making brilliant white grounds. Our whiting is dry ground from marble deposits in the United States. Dry grinding reduces it to a powder without destroying its particle structure, which is essential in making strong grounds and providing tooth on the surface of the grounds. The low surface area of our marble (when compared to precipitated chalk) keeps oil absorption low, which is ideal when adding it to paint and painting mediums. In painting grounds, it makes a durable surface with tooth for egg and casein tempera, distemper, encaustic, oil paint, and watercolors.
Both limestone and marble are calcium carbonate (CaCO3), which is also the composition of the mineral calcite. Marble is a metamorphic rock composed of recrystallized calcite. The metamorphism of limestone causes the calcite grains to grow in size and interlock with one another. The result is that marble is noticeably denser and harder than limestone. Limestone forms under deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores and hence contains invertebrate fossils. However, the metamorphic changes that convert limestone to marble almost always destroy these fossils.
Add to paint and mediums to create textural and bodying qualities to paint without affecting the color. Marble dust has a little color in drying oils, so it can be added to oil paint without affecting the tint of the color.
| Properties | |||
| Extender Pigment | Marble, Ultra-Fine | Marble, Fine | Marble, Medium |
| A premium, ultra-fine particle size, wet ground marble with a closely-controlled particle size distribution. NSF listed. | A fine particle size marble with a closely-controlled particle size distribution. It is the coarsest wet ground marble. Provides the lowest possible oil absorption. | A medium particle size marble featuring a careful control of oversized particles. | |
| Chemical Analysis | |||
| Calcium Carbonate (CaO3) | 95% | 95% | 98% |
| Silicon Dioxide (SiO2) | 0.3% | ||
| Typical Physical Properties | |||
| Mean Particle Size | 3 microns | 11 microns | 17 microns |
| Hegman Fineness | 8 | 3 | – |
| Brightness (Hunter Y) | 96 | 92 | 92 |
| Retained on 325 Mesh Screen | 0.003% | 0.1% | 11% |
| Moisture | 0.12% | 0.12% | 0.2% |
| Acid Insolubles | 2% | 2% | 3% |
| Oil Absorption | – | 9 g oil / 100 g pigment | – |
| Solid Density (lbs. gal) | 22.7 | 22.7 | 11 |
| Bulk Density, Packed | 60 lbs./ft3 | 90 lbs./ft3 | 109.5 lbs./ft3 |
| Bulk Density, Loose | 40 lbs./ft3 | 65 lbs./ft3 | 51 lbs./ft3 |
| Specific Gravity | 2.7 | 2.7 | 2.7 |
| Refractive Index, mean | 1.6 | 1.6 | 1.6 |
| Mohs Hardness | 3 | 3 | 3 |