2 replies to this topic

[sasman]

I have just managed to purchase some 5413 H super Aluminium powder ..

Now on Skylighters page it mentions "3 micron, coated. Eckhart #5413-H Super" .. Now it clearly says 3 microns..

Now on eckharts page See here it mentions That 5413 H super is <45 microns?.. Now that seems a lot bigger than 3 microns?..It also mention's wet sieveing? is that how they sieve fine powder with a liquid?

[Richard H]

Unsure on the particle size, but either way 5413H is the fabled 'dark pyro' aluminium and I trust you will use it very carefully indeed. It is likely the particle size will be much smaller than 45 microns, since the data merely states 'less than'.

[Mumbles]

From what I understand this is just a mistake in conversion. <45 is the same as -325 mesh. 325 mesh is the smallest practical screen size I've heard used. After this the wires are just too thick. They use something called the sedimentation method to approximate mesh after this point. It is described in Glitter: Chemistry and Techniques when talking about best Al. I don't know it exactly, but pretty much you add some powder to a liquid and stir it up. Depending on how long it takes to settle determines the mesh size. Each metal and particle shape has it's own value for different liquids used. This may be what they call "wet sieving", but I don't know for sure.

Anyway back off the slight tangent. Somewhere along the line, somebody got the idea that this Al was -600 mesh. With how thick the wires would have to be, the opening would be a very small micron like that. Thus when they heard that the Al was -600 mesh they looked up the microns, it was something like 3 micron, and it stuck. It is really annoying actually. If I had a microscope and a way to measure the particle size I would show the chemical resellers, and those morons on ebay, that their Al was more like 15-20 micron.

Edited by Mumbles, 21 November 2005 - 09:21 PM.