Putting a layer on an existing layer of epoxy- what grit sandpaper?

Hi guys, I've read online that you should sand the epoxy with course sandpaper (100 grit) and I also read you should sand it with fine sandpaper (200+grit) before putting on another layer of epoxy. What do you guys think? course or fine sandpaper?

Thanks for all the help so far I really appreciate all the amazing members of this forum!!!

 

If the epoxy has cured, and has an 'amine blush' on the surface (like WEST epoxy) you will have to give it a wash first before sanding it.
If it has not fully cured, you should be able to add another coat of epoxy without sanding.
The purpose of sanding the epoxy is basically to provide a 'key' for the next layer.
You do not want to be too brutal - if you are not careful, you could easily start removing material that helps to form the strength, rather than just lightly sanding it to 'key' it.
Other folk like @fallguy on here have a lot of experience with epoxy and can advise you better.

 

Epoxies have open windows where chemical or primary bonding can occur; some are 24; some longer, but I always sand next day to get rid of roughness.

Use 40-60 grit papers. You won't get good bonds polishing epoxy. You'll find rather quickly the fine balance between roughing the surface and cutting through light glass.

I use an rts400 festool and hundreds of sheets of paper so far. Epoxies are very hard on sanding papers.

You can also use peelply to reduce the need for sanding or develop a uniform sirface and no drips or runs.

 

Heavy grit will destroy the glass.
You won't see it very well.
120 is what I use, by hand.

If the glass weave is sticking out before sanding, you have really wasted your time and glass.