Wet sanding - hot to?

tinanFebruary 19, 2013

*oops subject was supposed to be "how to"

I need to wet sand my concrete countertop. Can I use a regular orbital sander with the discs with no holes (don't want wet stuff coming up through) plugged in to GFCI or will that result in potential hazard?

This post was edited by tinan on Tue, Feb 19, 13 at 22:20

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Is this for the purpose of exposing the aggregate and polishing the surface?
You can hone the concrete with dry diamond sanding discs, then polish it with wet polishing pads, but for that you would need an air sander or an electric one made for water exposure. It's gonna cost ya. The dry diamond discs are about $40 a piece. I bought a couple of them for my soapstone countertop project.

    Bookmark   February 20, 2013 at 6:22PM
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No I don't want a honed surface, just to remove the irregularities and rough spots left by my amateur concrete pouring and troweling skills. Dry sanding would create hazardous dust, this is an indoor project. I hand sanded part of it, but you can imagine that takes a lot of effort and destroys the wet dry sandpaper pretty fast!

    Bookmark   February 21, 2013 at 12:05AM
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Christopher Nelson Wallcovering and Painting

" Dry sanding would create hazardous dust, "

In what way?

    Bookmark   February 21, 2013 at 5:10AM
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Sophie Wheeler

There are specialty stone grinding equipment pieces that will cost you quite a bit. For the cheap version, you'll need an air compressor, an air powered random orbit sander, diamond grit sanding pads, and copious amounts of water. As in this is NOT an indoor project unless that indoor location is a basement workroom with a floor drain and a filter to capture the solids in the slurry before they stop up the drain. It's an outdoor project.

    Bookmark   February 21, 2013 at 7:26AM
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christophern, sanding concrete creates silica dust which is very harmful to inhale and impossible to completely capture even with a vacuum.

So it sounds like the consensus is no wet sanding with my orbital sander. I'll try the hand sanding diamond pads first, ordered them today. I can control the amount of water/surry and wipe as I go. I'm troweling on an overlay layer to smooth things out, after talking to the Rapid Set tech support guy, that may minimize my need to sand as well.

people do do this indoor,s as many countertops are pour-in-place, but I expect it to be messy - pouring the concrete was but I managed to contain the mess!

    Bookmark   February 21, 2013 at 12:11PM
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After the overlay layer, the countertop is pretty smooth. I only needed to sand some edges, and it's basically done! I am not going for polished concrete, this is a hand troweled surface. I ordered a set of diamond grot hand pads for stone and concrete polishing, they arrived yesterday and worked like a charm for removing some rough edges and rounding the sink edge a bit. They can be used wet or dry - wouldn't be great for large areas, but for edges etc they are good. A bit of the black/green grit wears off on the light gray concrete though.

    Bookmark   February 25, 2013 at 10:53AM
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