More faceting questions from the Mail Bag:
I have a quick couple of questions I hope you have time to answer for me. My bother-in-law brought back some Australian opal from his six month trip in Australia. Some of the opal is translucent and he wants me to try to facet some of it. I have never cut opal before and I warned him I had zero knowledge about opal. I know that opal is soft, Mohs hardness of 5-6.5 and heat sensitive so it should be cold dopped. I was planning on dopping the material with super glue to cut the pavilion and then transfer the stone using epoxy to cut the crown. I then wrap a cold wet paper towel around the stone and dop with epoxy glue to cut the crown and use a small torch to heat the dop attached with super glue and remove it. When the crown is done I put the stone in Attack and let it set over night to dissolve the epoxy. I could use super glue for both side of the stone and put the finish stone Acetone to dissolve the super glue or even use the same wet towel and torch process. Is there a better way to do this? I am concerned about the heat when I transfer the stone and the potential adverse impact the Attack or Acetone might have on the opal after I finish the stone. What are your thoughts. Do I cut the opal with 600 lap or do I use some other lap? Finally, what type of lap and polish do I use for the pre-polish and polish? As mentioned above, I have never cut opal before. By the way, I use two of your designs, the Hexa Brilliant #5 and Bare Square #3 OMNI version, to cut a couple pieces of Cristinite. They turned out great. Thanks for sharing! I take your designs and rebuild them in Gem Cad. I figure if I can't rebuild them, then I don't understand the design. I still have a lot to learn about Gem Cad. Even with all the information in front of me, I have trouble building many of the designs in Gem Gad. I will be a long learning curve me to learn Gem Cad. Again, thanks for all the help you have provide me. The BA5T's and diamond powder for corundum are fantastic. The made polishing sapphires a joy. The Corian laps with the Voodoo Magic work for just about everything else. I still have problems polishing quartz but I will figure it out one of these days. Cheers, Mike Hi, Mike
Thanks for the kind comments and the good feedback re BA5T laps. Make sure you let Jon Rolfe know you like them, too…
As far as polishing Quartz, *everyone* has the issue – Quartz can be a real frustration. Thankfully, there are some emerging strategies for that. I’m about to release Voodoo Chrome; I’m experimenting with a Voodoo Zirconium for Quartz; and Jon Rolfe also has a couple of new laps out that are likely to be better for Quartz than most of what’s available right now. He’s got a “green wing”, and “cream way“, and a hybrid “mint way”. I haven’t had a chance to test those YET. We did use Voodoo Chrome at the last academy and it *killed* on the Quartz we cut there. Availability on that is some few weeks out…
Your approach to using GemCad is really good: Getting the feel for a design in GemCad before you’re grinding on a stone is SMART. I use this strategy myself – even on my own designs, if it’s been a while since I’ve cut that one. Much better to be very clear what you’re doing and how the meets will come in than to over-cut due to confusion or mistake…
As for faceting Opal, I don’t recommend faceting unless it’s VERY clear. If the Opal is very cloudy AT ALL, it’s going to be a dead-looking piece, and probably a waste of time and material. This is SUCH an issue, I even have a special lighting technique I use for materials like Opal and Rose Quartz to evaluate their suitability for faceting.
So, if the Opal is translucent, I recommend against faceting. You’ll have better ROI by carving or cabbing.
As for dopping Opal, I’m a fan of minimizing both heat shock and chemical shock to the material. I usually put a blob of wax on the dop, and then use my tabling adapter to grind that flat. I superglue to that wax for initial dopping. After transfer you can release via mild warming or via a jeweler’s saw, or even a hot knife.
I’ll usually use epoxy in the cone dop – with a blob of some kind of no-stick on the culet to prevent shrink-breakage (vaseline or something like that). I will usually release the stone using a technique taught to me by Carl Unruh: I put the stone and dop in a double boiler and SLOWLY run the temperature from room-temp up to a rolling boil. I put the stone and dop in an orphan sock to prevent dropping or chipping. Working through the sock, I use a wooden utensil to push the stone off the dop. Then, leave the whole thing in the double boiler, turn the heat off and walk away until it comes back to room-temp on it’s own. This is a very cautious way of doing things. And, one must make SURE that the epoxy one is using will heat release around 200F. Loctite brand 5-minute epoxy is what I usually use. It also won’t respond well to Attack, but cleans pretty easily with Easy-Off oven cleaner (lye).
As for sequencing Opal, I don’t cut many smaller pieces because it won’t pay, so I’m usually cutting at 600, pre-polishing on a Red Raytech 600 NuBond, and polishing these days with my new Voodoo Chrome (which will be available very soon).
I hope this stuff is useful, and hope that you keep in touch. Thanks again for writing with the great faceting questions!