How to get a crystal clear epoxy finish after filling cracks/voids in slabs??

Sam Keays

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6
Hey all,

I have some damage to the end of a slab that I would like to preserve with epoxy instead of cutting the damage off.

I have tried this before on small sample pieces and I am not getting the result I'm looking for. I want the finished result to be a clear epoxy fill that is smooth and level with the rest of the slab. I slightly overfill the void with epoxy so that when it settles in, it's pretty close to flush with the rest of the slab surface. When I go to sand it smooth to match the table surface, I am using 220 grit on an orbital sander and it just seems to make white and cloud scratch marks all over the epoxy, therefore making it unclear.

What is the best way to sand/smooth the epoxy down flush with the slab surface, yet maintain a crystal clear finish in the epoxy??


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Hey Sam, I don't know, but just wanted to let you know I deleted the duplicate thread that was in General Woodworking. This is the right place to get an answer! :thumb:
 
Sam,
I think you stopped sanding the epoxy part too soon. If you keep going through the grits the scratches will get finer and finer. Just keep going until you are satisfied and then do a final buff to see if it's clear enough. I usually go up to 1500 grit (wet).
 
Sam,
I think you stopped sanding the epoxy part too soon. If you keep going through the grits the scratches will get finer and finer. Just keep going until you are satisfied and then do a final buff to see if it's clear enough. I usually go up to 1500 grit (wet).

Awesome thanks Ted. This next part may sound like a dumb question, but are you sanding wet through all the grits up to 1500? And this may sound even dumber, but how are you sanding wet? Just by simply adding a little water to the surface being sanded? Or are you using a special wet polisher?


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Sam, I need to qualify my methods. I don't do a lot of flat work, so my method is used on bowls, but it should translate. For flat work I'd go dry as far as my paper selection would take me. I can go to 800 grit before I have to switch to wet/dry paper worked by hand with water lubricant, and that may be good enough. I see maybe two problems with doing a slab. One possible thing is that sanding the area of the epoxy to a very fine grit to get a clear finish would affect the way the surrounding wood takes your final finish. Usually, the smoother the wood the less finish gets absorbed, so that spot next to the epoxy might look different. Another possibility is that wet sanding will put an epoxy/grit slurry into the grain of the surrounding wood and that will affect the finish as well.
Maybe someone with a little more slab filling experience will chime in.
 
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For holes I mix 50% epoxy with 50% acetone, then add sawdust and pack it in the holes leaving it a bit proud. Wait until it cures, sand, then use the same finish that is on the rest of the piece
 
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