One of my biggest issues when I started electroforming was trying to find out the true size of my ring. Often, the epoxy would create a lump on the inside of the ring behind the stone leaving huge gaps when I put the ring on my ring mandrel to find out the size.
There are a couple solutions to this issue that I've found to be extremely helpful, you'll need a few tools to do this.
Method 1: Using The Right Ring Sizing Tools
So you have a ring that's not completely round. I bring you one of my first rings that I have refused to sell since I've gotten much better at ring making using this medium, so it just sits in a box of rejects.
You can clearly see the flat part where the epoxy was placed behind the stone. When I put this ring on my round ring mandrel to see what size it is I don't get an accurate measure because there are huge gaps between the ring and mandrel.
You'll never get an accurate size if your ring doesn't sit flush to the mandrel on all points. There is another ring mandrel that can help fill in those gaps better. It's a mandrel with a flat edge. This can often be all you need if your ring just has a small part of flat area and the rest is perfectly round. But if not, then you'll need a set of ring sizers.
Let's try putting this ring on the flat edge ring mandrel and see how much of a gap we get.
It's a lot better, you'll get a more accurate size than with the round ring mandrel, but, you can see there are still gaps. This is when the ring sizing set will come in handy. Check to see what size your ring is sitting at on the flat edge mandrel. Find that size on your ring sizing set, go up one size, and try the fit on your own finger.
Hopefully the ring isn't too big on you because it will make it that much harder to find the size. Try the ring on after trying on the ring sizer, does the ring feel tighter than the ring sizer or looser? Go up or down in size using your ring sizing set to match the fit to the ring. Find the closest fit and that's your ring size.
Method 2: Remove The Gap
Yup, it's as simple as that. The epoxy is only there to act as filler, to fill the gaps between stone and metal so you have a good sturdy base. Technically, you don't need to apply epoxy to the inside of the ring. So here's what I now do to make perfectly round rings.
I still apply my epoxy the same, inevitably it gets on the inside of the ring. But once that epoxy dries, I take my super handy needle files, the half round one in particular, and file that epoxy all the way down to the ring shank on the inside of the ring.
The right ring is what my ring looks like after applying epoxy, the left ring is what it looks like once it's all filed down so that the epoxy is only filling the gaps. Next, I paint with conductive paint then electrofom in to a perfectly round, easy to size, ring!
If you have any questions please leave them below and I'll get back to you!
*Note: I apologize for the super small last 2 photos. I'm working on taking new ones so you can see better detail.