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Written by Administrator
Wednesday, 01 October 2008 19:05

Apply dry developers the right way

October 2008

One of our readers sent us a comment about dry developer grain size.

Here is his letter, edited for a better understanding:
‘‘The technical data sheet of the dry developer xxx shows there is no particle sized under 0.1 µm, while you state a 1/100 µm (10 nm) figure. If the dust-storm cabinet comes with a 5 µm filter, no particle at all may go through; hence the developer formulae is not modified.’’

Here is our answer:
The dry developer xxx is not the only one of its kind on the market. Further without giving away any industrial secret, you may know that dry developers comprise magnesium silicate, alkaline earth carbonates, amorphous silica and other additives, for instance to enhance whiteness or increase fluorescent indications seeability under (UV-A) radiation.

Top quality dry developers are made from synthetic materials: there is no asbestos (so no asbestosis risk), silica is crystalline silica-free (no risk to induce silicosis). Asbestos was found in some dry developers 30 years ago. It may come with some "natural" raw materials.

Amorphous silica as found in some dry developers formulae may have a very small grain size.

As far as we know the first step to amorphous silica is to have silica (SiO2) react with fluorine, become then the silicon-tetrafluoride which is now atomized at very high temperature to give back silica -- totally amorphous silica, in the form of nanoparticles.

The average grain size of this silica is 12 nm, i.e. ca 1/100 µm.

The Van der WALLS forces then helps particles to coalesce together, but a significant part of the powder is made of independent nanoparticles.

Last Updated ( Wednesday, 25 May 2011 19:18 )