He gave me a ring for our third anniversary which would be too big for my ring finger but fit his perfectly! We commissioned a ring of the same design to fit my ring finger and now we have matching rings! But my ring is definitely too feminine for him.
I thought - I should be able to cast a ring with tools and instrument in the dental lab, as the steps to fabricating a dental crown and jewellery are quite similar.
1) obtaining a wax Model. Start from scratch with jewellers' wax ring blanks.
or with a ring that fits made out of cheap metal. Take a mould of it and flow wax in the putty. You could modify it's shape.
2) Sprue, invest and cast
4) If there are large porosities, consider soldering. Could also electroplate at a jewellers.
Thank you Chia and Melissa, the best friendly lab techs one can find!! Wouldn't have been possible without your help and expertise.
Step 1: Have a Ring in His Size
He gave me a ring for our third anniversary which would be too big for my ring finger but fit his perfectly! I commissioned the same ring to fit my ring finger and now we have matching rings! But definitely too girly for him.
I thought I should be able to cast a ring with tools and instrument in the dental lab, as the steps to fabricating a crown and jewellery are quite similar.
Step 2: Modify Ring to Liking
If you are already happy with the shape of your current ring (possible a ring of cheap metal in the right size), you can skip this step.
This modifying of the ring's shape could be done after obtaining the wax model but as the ring was quite thin, I preferred to build it up first so it would be more sturdy when removing from the mould.
Built up with expired composite resin - definitely more expensive than wax.
If it's the right size, try not to get any CR on the internal fitting surface of the ring.
Try in the ring on his finger to check how it looks.
Step 3: Making a Mould of the Ring
I used putty to make a two-part mould. (my one part mould failed).
Push putty into middle of ring then push it back downwards to reduce bulk at the center.
Make sure putty covers around half of external part of ring too.
After that has set, make other half of putty mine kind of bonded together still - you might want to put vaseline between the 2 layers of putty.
Step 4: Wax Model From Mould
Flow wax into mould carefully, making sure there are no air bubbles.
My plan was to melt both half and put the 2 parts of the putty together but that didn't work as I couldn't get both halves molten. Anyway, doubt if it would have come free from the putty.
I removed both halves from the putty (unfortunately in a few pieces) and melted them together (hot blade between the 2 halves).
Step 5: Shape Wax Mould
Shape wax by adding wax, smoothening wax. When happy with shape, smoothen with sand paper.
I used rough black sandpaper usually used to polish dentures, and 3M interproximal polishing strips.
Try on wax Model on his finger to check fit. A bit snug is better as you would need some excess to polish off later - this ring turned out slightly too loose for him.
Step 6: Sprue and Investment.
When satisfied with shape, add sprues. My friendly lab tech, Chia, helped me with this.
Note: my sprue was insufficient. Should have it thicker, longer or with a button reservoir.
Step 7: Casting.
I had help with this step.
Lodestar (6g) was used.
Step 8: Polishing
As it can be seen, my ring didn't have a sprue attached due to insufficient alloy used. This resulted in porosities.
Remove the excess metal with a disk. Polish with rough green stone, brownies and greenie.
Don't polish the internal surface too much or it might get too loose. My original ring fits on my thumb and I check fit of the new ring that way. Of cos it would be best to check on the recipient of the ring.
Step 9: Solder
After polishing, there were still quite a lot of porosities.
Just as we can solder PFM crowns for tighter contacts, we could solder the porosities :p
Drill porosities for a larger, rougher surface. Sandblast. Place flux and heat till red hot. Add solder.
Polish so soldered areas are flush. We used gold orthodontic solder so it appears a lighter yellow than Lodestar's gun metal grey. I going it's less obvious than a large porosity.Looks a bit like fried eggs to me. Yum.
The lab techs suggested bring it to the jeweller's for electroplating to get rid of porosities but we like it's grey gun metal colour.
Step 10: Get Married!
So it's not perfect, more of an organic shape with some speckles and little gold fried eggs. But it's the effort that counts :)
A solid ring with a unique gun metal colour.