Diatomaceous earth

I thot it was dead little plants.

[Herman]

I did some reseach, and of course started here: http://en.wikipedia.org/wiki/Diatomaceous_earth

DE is Kieselgur. A natural form of Fumed Silica. The industrial produced types have brand names like cab-o-sil, aerosil, fumed silica, amorphous silica, colloidal silica, whatever you name it.

Which makes life simple, as this is being used in composites all the time. Usually your thixotropic polyester resin has it, gelcoats, epoxy glue, etc.

But also bread, cheese, drugs (Fumed silica makes ingredients flow better during production) and many more applications than you would like.

DE is a natural material, and comes in many variaties, many with more or less wanted properties. Some are very sharp, some are cristalline, causing silicosis. Some are amorphous, which is the form that equals the fumed silica made industrially. The above mentioned link provides some good info.

[troy2000]

A quote about safety, from Herman's link - for those who don't want to read the whole article.

Safety considerations

The absorbent qualities of diatomite can result in a significant drying of the hands if handled without gloves. The flux-calcined form contains a highly crystalline form of silica, resulting in sharp edges. The sharpness of this version of the material makes it dangerous to breathe and a dust mask is recommended when working with it.

The type of hazard posed by inhalation depends on the form of the silica. Crystalline silica poses a serious inhalation hazard because it can cause silicosis. Amorphous silica can cause dusty lungs, but does not carry the same degree of risk as crystalline silica. Natural or dried diatomite generally contains very low percentages of crystalline silica. Diatomite produced for pool filters is treated with high heat (calcining) and a fluxing agent (soda ash), causing the formerly amorphous silicon dioxide to assume its crystalline form.

The crystalline silica content of the dust's particulate is regulated in the United States by the Occupational Safety and Health Administration (OSHA), and there are guidelines for the maximum amounts allowable in the product and in the air near the breathing zone of workers.

[Herman]

Thanks for quoting, health is an important issue. Protect yourself!

[Submarine Tom]

In it's pure form it is simply diotom skeletons minied from old sea beds where they settled to the bottom after dying many years ago.

Breathing the dust has a cumulative damaging effect so is to be avoided. The skeletons are razor sharp and very small (5 - 30 microns).

They make for a terrific parasite controller in the gut of any mammal (food grade only) and a fantastic pest suppressant in the

garden when applied in a water solution.

Around here, it can be purchased for $2US - $10US per kg (food grade) depending on quantity.

-Tom

[SeaJay]

Thanks for all of the feedback. I'm not worried about the health issues...its like anything else, use proper precautions. It can't be any worse to breath than microballons or cabo-sil. I think I'll give it a shot as I have a bunch of it for my pool filter and it is less money than cabo-sil.

[gonzo]

Microballoons are not too bad. Cabosil is. My concern with it, is that fumed silica sold as a load for epoxy is water free. Something sold to be used as a water filter may not need to be.

[Herman]

I have no idea of the situation in the UK, but here most fumed silica is Aerosil (Degussa) which is relatively water-free. I do however suspect that it is slightly hygroscopic. Once I get my industrial oven (it is ordered) I might run a test by heating a 20 liter pail with Aerosil for a while, and weighing it before and after (I have a 5000 gram scale, in 0,01 gram increments)

[gonzo]

Aerosil and Cabosil are the most common brands. They are very hygroscopic. If you leave the container open they make lumps and eventually become solid. Fumed silica has be treated at high temperature.