Talk:Colloidal silica

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I've left a note on the editor's talkpage already, but is there any difference between "Colloidal silica" and fumed silica? I first encountered the term colloidal silica when searching for fumed silica/cabosil for use as a resin thickener at my local boating supply store. It appeared to have the same properties as the fumed silica to which I was accustomed. If they are the same thing, it would be good to merge the two pages. -Verdatum (talk) 15:34, 27 January 2009 (UTC)

Yes there is differences between colloidal silica and fumed silica. The first is made a bit similar precipitated silica, but have smaller particles and is not porous - so it resembles a fumed silica. A colloidal silica is delivered as a suspension and precipiated silica is delivered as a dry powder. The applications are also different. I think the different types of silica needs separate pages or else the main page would be very extensive. The pages needs further extensions, but it takes some time. --Langbein Rise (talk) 18:25, 27 January 2009 (UTC)

Thanks! This explanation, as well as the article makes sense to me, given my understanding of the word "colloid". Yet, when I bought this product labeled colloidal silica, I found a perfectly dry fine powder, as if to suggest that colloidal silica is silica used to create colloidal suspensions. No matter. A web search seems to support what you've stated. Another thought, again knowing next to nothing, could this have anything to do with what I've heard about hydrophilic vs. hydrophobic fumed silica? I understand the two exist, but don't know anything about how their chemical makeup or manufacture differs. -Verdatum (talk) 20:05, 27 January 2009 (UTC)

Hydrophilic silica is normally untreated, but have many silanol groups (>Si-OH) on the surface making it hydrophilic. Hydrophobic silica is any type of silica treated with hydrophobic groups.--Langbein Rise (talk) 20:22, 27 January 2009 (UTC)