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I am wanting to do a project where I make a paperweight which will look like a cutout from a pond, with koi swimming in it.

So, I've 3d printed some koi. I made a moldbox, put in a thin layer of silicone, and then stuck a smooth metal air can on top of that. I then filled in the walls and removed the air can, so I have a silione mold of a smooth cylinder with a small lip at the very base..

My plan is to fill it with normal resin for about a 1/8 of an inch, cure it, remove the disk, based it, and then re-insert it into a mold. I think the lip will hold it in place pretty well. I then plan to add some water clear resin, add a fish, and repeat as needed until the mold is full.

My concern is that whenever I've filled a wide flat area with resin, it's never been really level, it's always is a little raised on the top where the resin touches the mold wall. How do you deal with that? I assume sanding, but if you're sanding it... how do you return it to being water clear - what grits of wet paper would you use?

Or is there some other, better way?

That meniscus will remain with most resins. The concave meniscus is a thing when you underfill, it goes convex when you slightly OVERfill. It's a liquids thing.

The good news is you CAN remove it AND buff it back to shiny, but it's neither fast nor effortless.

You'll need multiple grades of sandpaper (I've used up to 2400grit for metal polishing in addition to a polish for example) AND polishes and a few hours of work, minimum. Brass polish, silver polish, toothpaste. Wet sanding AND dry sanding. There a series of videos on the nets where people embed things into a clear cubic resin cast then machine it into a sphere as well as fully polish it back up, so it's definitely doable - it's whether you think it will be worth the effort.

The same way computer case modders used to have to polish the scratches out of their acrylic inserts years ago (because clear plexi accumulates scratches just from you running your finger across it.

this video here demonstrates using masking tape and slightly overfilling the resin to create a convex meniscus. It might be a bit difficult to completely redo your mold, but this does held.




basically, if you can get your walls to exactly the right height that helps.

You could also try doing it so it's go the slight raise on the edge, wait until it's dry, and then remove the walls, and add a final layer of resin, using the slightly raised bit as a "wall".

I'm not sure if that'll give you a completely clear edge, however.