What is Colloidal Silica?

[Medskipper]

In the June issue of MBM they have an article on GRP repairs. Now I have done a few of these in my time! I always use a gel coat in the final stages of the repair but they suggest in step seven that you use Colloidal Silica to thicken the gel! I have not heard of this before and wonder if anyone has used it and to what effect? Where would you purchase it?

While we are on the subject, I have always found that a large repair of this kind is far easier to do and made to look good than a scratch in the gel coat that is too deep to just rub down or compound. Does anyone know how to deal with a scratch of this kind? too deep for compounding and too shallow to fill properly? Is the trick to make it much deeper and then fill, rub down and then compound?

Regards Barry


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[coliholic]

SP Systems on the Isle of Wight sell it, http://www.spsystems.com it's also known as micro ballons although micro balloons might be a bit different now I come to think of it. Comes in quite a big tub (5 inch dia about 4 inches deep) that weighs virtually nothing and costs about a fiver a tub. Mix up your gelcoat and hardener and then spoon in as much of the CS as you want to get a nice thick consistency and the gel coat will then hold on virtually any surface without sliding off. Also very good to use with epoxy 'cos you can't get a gelcoat as such for use with epoxy so you just thicken up the "top layer" using the CS. Good stuff, works well.

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[coliholic]

SP Systems on the Isle of Wight sell it, http://www.spsystems.com it's also known as micro ballons although micro balloons might be a bit different now I come to think of it. Comes in quite a big tub (5 inch dia about 4 inches deep) that weighs virtually nothing and costs about a fiver a tub. Mix up your gelcoat and hardener and then spoon in as much of the CS as you want to get a nice thick consistency and the gel coat will then hold on virtually any surface without sliding off. Also very good to use with epoxy 'cos you can't get a gelcoat as such for use with epoxy so you just thicken up the "top layer" using the CS. Good stuff, works well.

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[cliff]

SiO2 with a particle size of 1~5 nano metres althought this can be as high as 50 ~ 60 nM.

Used extensively in the paper industry and as a thickening agent for epoxy and other manmade resins.

West System do one as do other "resin suppliers"

Be careful of the dust and please don't sneeze when you have a spoonfull of it in your hand - it will go everywhere.

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[gjgm]

any fibreglass specialist will supply it, but it does seem to come in rather industrial volumes! But a carrier bag size weighs about 5g i d think. Dont mix it too thick into gelcoat or you ll find it doesnt "dissolve", and you ll get a grainy paste.

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[itsonlymoney]

Dont know the answer to your first question but regarding the "scratch" the answer is yes it is neccasary to make it deeper in order to take the filler. A dremel tool works well or just gouge it out manually.
Ian

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