Quartz for filler

[Chris...]

Silica

Hello all!
What exactly should I look for when buying silica to mix my own filler?
Is it quartz powder what I´m looking for and what´s the right particle size?
I will buy from Kremer Pigments, here in Germany. They also have stores in the U.S. and a website in english.
www.kremer-pigmente.de/englisch/homee.htm
But i´m a little bit confused by the offered variety.
So could someone have a look at their catalogue, please, to tell me which one´s the best for the purpose.
www.kremer-pigmente.de/intl.catalog/epigmen14.htm#fillersfromstone

Thanks,
Chris

 

[jecollins]

Consider glass bubbles

Instead of silica, you can get very low density glass bubbles as a filler material. The stuff looks and feels like powder, but it's very lightweight. Here's a reference: http://products3.3m.com/catalog/us/...erials_3_0/command_AbcPageHandler/output_html

 

[Chris...]

So it seems like there´s no `too fine´. I was even more concerned too use something too coarse.
Some time ago I got some quartz from a crushing mill (?) I came by. But it looks more like the sand you see in hourglasses.
With glass bubbles would you use the same amount of weight? I guess they will significantly increase the volume of the mixed filler compared to silica. But that should be just fine.

Cheers,
Chris.

 

[jecollins]

Bubbles are much lower density than silica. Basically they are hollow beads of silica. So if you go by weight, you will have WAY too much, by at least a factor of 10. Go by volume or by texture. I would just add the bubbles until it was a good "spreading" consistency.

 

[Pam Wedd]

Hi Chris
I think the finer the better. I use to get stuff called Minex 10, from my pottery supply store, then the next time it was Minuex 4 and then finally Minex 2 - although you couldn't really tell to look at, it was progressively less fine. I think if it is too coarse then the particles don't pack tightly enough, making the filler more porous to moisture migrating from the inside out, and leading to paint blistering.
The finer silica, the tighter it packs, the less moisture migration, the less chance of blisters.
This is my latest theory. For what it's worth.
Haven't heard of these glass beads but anything to save weight.....
Good luck.
Pam

 

[Dan Lindberg]

I tried, (maybe not hard enough) to mix the glass beads into some filler I was mixing, and I couldn't get them to stay down, ie, they would float to the surface when ever the mix was allowed to sit.

On my last project, I replaced about 1/2 the silica in some OT filler with cab-o-sil and that worked OK. While the cab-o-sil isn't as light as the glass beads, it's a lot lighter then the silica. I think this saved about 6-7 lbs in the weight of the finished canoe, a 17 ft OT. The cans were old and the silica settled out, so I just left it there on 3-4 of the 5 - 1 qt cans. I replaced it with an equal volume of the cab-o-sil.

Dan

 

[Chris...]

So far, thanks folks!
Now we have silica powder, colloidal silica/cab-o-sil and glass bubbles.
And there´s also diatomaceous earth.
Think, i´ll have to make some tests...

By the way Pam, interesting website you got there.
Great article on painting and the photo of your canoeing cat made my day! Thank you!

Chris