5 replies to this topic

[Deano 1]

I recently read ( but can't remember where ) that the dark in dark aluminium was charcoal intimately milled. Does anybody know if this is right, if so is it safe to mill AL powder and charcoal with stainless balls.

[MDH]

That's incorrect. The process used in Indian blackhead invloves burning sheets of aluminum with paper in between it in an atmosphere with no oxygen. German is dark because it is fine mesh.

[Deano 1]

That's incorrect. The process used in Indian blackhead invloves burning sheets of aluminum with paper in between it in an atmosphere with no oxygen. German is dark because it is fine mesh.

Thanks for that. If you think about it, the paper burnt in an oxygen free atmosphere is just charcoal. Time for experiments me thinks:rolleyes:

[digger]

Thanks for that. If you think about it, the paper burnt in an oxygen free atmosphere is just charcoal. Time for experiments me thinks:rolleyes:

There has been allot of debate on this point. I have genuine Super H and it is not black. It is described by them as stearin coated aluminium flake (the stearin added as a coating agent during milling). The spec is produced from 99.5% aluminium, it lists the acetone soluble content (stearin) but no mention of carbon.

Here is a link to the spec Click Me

[Potassium chlorate]

I have genuine German Black too, and it's not black but greyish, although more grey=not bright, than uncoated flakes.

However, the black Al that is black isn't bad either and usually 30-40% cheaper.

[pyrotrev]

Most very fine metal powders tend to be grey...black in colour regardless of the colour of the bulk meteal when polished - it's something to do with scattering/absorbtion of light by irregular surfaces. The only ones I've ever seen that look metallic were some quite fine (6...9 micron) aluminium flake powders with quite a high stearin content that seemed to have the individual flakes sticking together in an oriented fashion (like slates on a roof) to form larger reflective units.