If you make a resin piece in a mold or frame, or even if you create a dam around the edges with tape or similar, you will almost certainly get a sharp, unattractive and unwanted ‘lip’ around the edge of your resin. This is from the meniscus effect where the resin holds on to the surrounding edge in a tiny curve, the same as water in a glass if you look really carefully. Resin creates a concave meniscus, resulting in this little sharp and raised edge once it is cured.
So, how to fix the lip of the edge of your cured resin?
Well, it all depends. If you plan to trim down your piece at the edges anyway, then the lip will be cut off when you trim the sides. Problem solved.
But a lot of the time, our pieces are not intended for, or not suitable for trimming. So that means we just have to deal with it.
In this video, I am treating the lip on a resin and alcohol inks piece, that has been poured into a round mold to use as a coaster. But the process would be the same for a larger resin piece too. I then cover the entire back of the piece with another thin coat of resin, and dome it right up to the edges. But you may also wish to brush just the edges of the piece providing you can keep your sanding marks just to the very edge. You can do it if you sand carefully just along the lip. You could also sand with a rotary tool just to remove the lip along the edge and then brush on a thin resin top coat just to cover the edge.
Check out my earlier video and article on how to fix flaws in resin where I brush on a very thin coat to cover scratches in a piece that has been selectively sanded.