CUTTING /STABILIZE ETHIOPIAN OPAL

[sedaopals]

Ethiopian opal has a high water content and un less treated a large majority will develope stress fractures.I still have Ethiopian stones i cut which are still intact after 5 years.Keep your rough opal damp until you cut it as the matrix and opal work against each other when complety dried out.When rubbing down i dont use steel wheels due to the vibration.My progression is 280-600-1200-3000 grit wheels.I use a fine trim saw to cut of any matrix.I also use a lot of running water when rubbing and polishing the stones.After the inital rubbing i set the stone aside near my work lamp to check for any cracks.If this happens i cut it away and re shape the cab often with no futher cracks.I tend to cut the cab a bit on flat side as its seems to show off the colour more.
If you buy material in the rough you can keep it as a natural specimen ,cut a cab and hope it is ok or you can stabilize the stone as follows.
OPTICON
Opticon is my main form of stabilizing Ethiopian opal.
-Immerse the stones in a canning style jar filled with enough resin to cover the stones and tighten the lid so water cant enter.Condensation can turn the resin cloudy.
-Place the jar in a ordinary slow cooker filled with enough water so the jar dosent float.
-Turn the heat up to 150-170-use a thermometer to check the temp-i use a kitchen meat thermometer.
-Strain off the excess resin and place on tinfoil and vacume for at least one hour.
-Using a artist style brush paint the stone with a weak mixture [40 to 1] of resin and hardner and re vacume for 15 minutes.
-Remove any excess moisture with a acetone cloth.
-When the stones are no longer tacky polish or re polish as the case may be.
GLUES
I have also pre rubbed the stone and heated it under strong lights and applied a super glue for glass covering over the stone and then finished polishing it.There is one other product which i havent used but HXTAL glue for glass also works-you will have to search the internet for more information on that one.
If you sell the stone you will have to mention it is treated to the purchaser.Some of the colours of Ethiopian are amazing and these methods will preserve the stone.
With some specimens i have that are badly fractured i soak in parrifin oil.This may be absorbed in to the matrix but it makes the specimen look fresh and shines as if its in water.
TERMS USED BY SELLERS
HYDROPHANE -an opaque variety of opal that becomes translucent or transparent when wet. You can test your opal by placing it dry under a light -wet your hands slightly and what sticks to it is hydrophane.
GUM OR BUTTER OPAL- A light weight porous material -can be with neon colours.Called gum as its like chewing gum and sticks to your finger.Keep dry.This material can be cut dry or hydrate slowly for a few days.
Dont dunk in water suddlenly as some have been known to explode.
Have fun cutting.
Regards Paul Sedawie-

[opalfireinfo]

Hi Paul,
Thanks for the tips on stabilizing this new opal.
Do you use opticon on the wet stones or do they have to dry first? Does the opticon affect the color the way water does?
Will the opticon seal a damp stone so the color enhancement from the wetting stays, or will it dry out eventually?
Can I safely cut a dry piece and expect it to not crack later?
What percentage am I likely to lose to cracking?
How heat sensitive is it? Can I safely use dop wax?
How can I tell if my opal has been soaked in oil? Isn't that a very bad thing to do to opal? How can I safely clean it if it has been oiled?
How much weight will I lose if I buy the opal wet or damp and it dries out in transit? I'd hate to buy or sell a parcel and have it significantly lose weight in transit.
And finally (you thought I'd never end) what about durability of the cut stones? if they are soft, can they safely be set in a ring?
A related question is: Will the opal change every time it gets wet after it is cut and set? I'm afraid that my average customer will be unhappy if her opal loses all its color every time she washes her hands!
I can see that it is softer than Aussie material, but is it really brittle, as I have heard? So is it safe to set a domed cab in a ring? Is it even safe to set, or will all my jewelers hate me?
Ok, enough questions....I'll have more later I'm sure...
Thanks for all your help, Paul, I hope you can give me some guidance here. This new opal is so pretty, but I don't want to to cause me problems down the line...
Mike

[opalfireinfo]

Hi again Paul and all,
So I notice that Paul's instructions include using a vacuum pump to suck the superglue into the opal.

But I don't have a vacuum pump. Am I doomed?

My solution so far has been to offer rough for sale, I haven't cut any yet, still hoping for more info. I wrote Paul off-forum with several more questions and I hope he will reply here.

I have received several sets of instructions for cutting this Welo from various sellers of rough and cut opal. All of them have sworn me to secrecy, however, so I can't tell you what any of them said.

But the advice sets were mutually exclusive, so everyone can't be right, or can they? Could it be that this opal CAN be cut most anyway you want, and it isn't as sensitive as we think?

I guess it depends on the rough too. I'm inspecting every piece before I list it to be sure it has no cracks, so the glue stage won't be necessary with my rough. I don't understand why someone would cut and polish cracked opal anyway.

I haven't determined yet about the sealing process. This goes against everything I believe about gemstones. My hope is that a complete polish, front and back, using an oil suspended diamond paste, will seal the opal well enough that no coating of the stone will be necessary. My worry is that it will continue to be hydrophane and the stone will change radically every time one of my customers washes her hands.

I mean, if we're treating it and sealing it and gluing it together and lord know what all else, we may as well be cutting andymoo concrete or Louisiana sandstone.

My solution will be to try several of these methods and report back with my results. I'll take some pictures too and try to describe what happens.

Stay tuned, same bat time, same bat channel....mk

[Iceopals]

I'm really looking forward to hearing about your cutting results. And to be honest, I think there would be nothing cooler than a ring that changed it temperament every time I got it wet. So don't go thinking that's necessarily a bad thing. Just not something you guys might like! As for the vacuum system, I'll bet it's to remove any air bubbles from showing up floating just below the cured surface, or breaking out after the glue is cured, rather than sucking the glue into the voids... Well, except for those air pockets that are possibly keeping the glue from filling in...............

[opalfireinfo]

Hi Ice and all,
yep, it amounts to the same thing, air comes out, glue fills space. I've seen it used before with super glue and epoxy and it works great. There are a lot of materials that it is commonly used on. I can see it for a specimen opal too, gluing and sealing, no problem. But to fill cracks with paraffin oil, as Paul suggests, or to vacuum pump a glue or filler into cracked rough, well... Or to sell a cut stone that is hydrophane and has CA holding it together? Is that courting disaster? As I recall, superglue isn't waterproof, and a stone with CA in it that gets wet and dries out may be weakening the bond with the CA film, especially as there's an expansion and contraction of the stone as it wets and dries.
Maybe I think too much.
mike

[Iceopals]

Not thinking too much! But I'm such a purist, I dislike stabilized material unless it allows material to be used that otherwise would be trash. But maybe it should go into earrings or a pendant, that wouldn't get wet so much? Now, a nice hydrophane stone without the cracks............

[opalfireinfo]

Hello all,
Time for an update. I've sold a few pieces of this new Welo rough, but I haven't gotten any reports back from cutters yet. I've asked some to respond here with their results so all can share the info.
I started cutting some pieces that I picked up from one of the sellers here, altho they aren't offering rough anymore. I haven't finished because i decided I wanted to let them dry before moving from the wet stages to the diamond compound stages.
I was told by the vendor to cut it dry, which I don't think I want to try. So I cut some wet and it handles like aussie except that it is soft. So a very light touch is necessary. I'm dopping with wood glue on a wooden dowel, but others report success with green wax. Also, you have to plan your cut, with notes and drawings if necessary, since this hydrophane material will sometimes lose the color as it gets wet, so soon it looks like you are cutting clear quartz. With most of this, the color is throughout, so it isn't much of a problem. I used a 600 lap to shape it, then went to 600 diamond wet resin pad to sand it. Then I let it dry out. That's where I am now. Next I'm going to 1200 diamond compound on a poly-pad, then 3000, 14K, and 50K. if I think it needs it, I'll take it out to 100K, but that's rare.
I'm going right to diamond at 1200 because of my frustration with the wet color fade. I also bought a dehumidifier for the shop. Once those puppies get dry and bright again, I'm not getting them anywhere near water. I think the diamond compound will slightly seal the stone, since the scratches are getting smaller and smaller and the diamond is in a silicone oil slurry. I plan to polish the backs too, in hopes that will help seal it. I forgot to shoot pics before cutting but I'll shoot it when its finished.
I hope others will report their experiences with this rough here as well. I am particularly interested in how it works out all of the cutters out there. Remember, light touch...
Thanks,
Mike

[opalfireinfo]

Hi again,
After too long, I got them dry enough to work again. I don't want to wet them again, I now understand why the fellow told me to cut it dry, it takes forever to dry out. To speed it up, I'd recommend storing them in a sack of salt. I used rice, but salt should be better. In the tropics we always had rice in the salt shakers to keep the salt dry.
So I went from 600 wet diamond resin pad to 1200 diamond compound in an oil base. No color fade! Then thru higher stages to 50K. Turned out nicely, so what did I learn?
1. Water is a big pain. Paul's advice in the first post here must refer to older production. I'm cutting Gondar (Welo) white and clear base here now, I dunno what exactly he was cutting then, but don't store this stuff wet because the color fades. Water is useless with this stuff. I don't really understand why he is showing his rough wet when it won't look like that after cutting it. But the pictures look great. I am going to try shaping it with a 600 or even a 1200 bonded diamond steel disc and use oil as a lubricant instead of water. Light silicone oil in a spray bottle or drip tube should do it, these pieces don't need much shaping. Then I'm going directly to diamond pads for sanding and so on. If you do use water lube with your usual diamond cutting wheels or discs, allow time for it to dry before the polishing stages. Paul is probably correct about the vibration from steel wheels though. I use discs and I don't have that problem, but if your wheels wobble or run rough, it could be a problem. The good side is that this material is very soft. It cuts very fast on steel wheels so use a light touch.

2. It is brittle, so be careful along the edges. I wouldn't use anything rougher than 600 and I just got a new 1200 disc so I wouldn't have to use the 600 so much.
3. It does not like heat, so be careful in the higher grit polishing stages. It has a grain related to the color structure.
4. It is so soft, it scratches easily. High domes are beautiful in the magazines and jewelers windows but extra care must be taken for this material. Ring setting will be a particular problem and jewelers may come to hate us.
5. It's the prettiest thing I've ever seen.
Here are pics of my first two:


and



Please forgive the crusty edge (I've sanded it smooth) and the specks on the face of the opal. I had to have them there to focus on. The first one is a stairstep pattern, one of the "almost harlequins" we were talking about elsewhere on the forum.
I have another bigger and nicer, high dome cab which I scratched while removing it from the dop stick, hence my caution about softness. When I repolish it, I'll post a pic of it too.

I'm thinking that this material would be perfect for hand cutters, working with a couple of diamond files and some sandpaper, finished with rubbing compound or tripoli? Or even diamond compound?

I hope we'll get some more pics of the Ethiopian from others too.
Mike

[azvinnie]

Hiya' Mike. Thanks for the posts on cutting this rough. But I'm curious about the one that got scratched coming off the dop. As in just what scratched it. That would be a good clue about whether we need to buy some "kid gloves" to handle it.

Thanks.
Vince

[opalfireinfo]

no kid gloves needed, I turned around to look at something and scratched it against the side of my arbor. Not a common hazard.
I did take out an old well worn diamond file though, and worked it out by hand. Just the dry file, and I'd tap it on a towel to clean off the swarf. I find this material to be easy to work by hand, I'll have to try a dremel on some of it, well, my old foredom flex-shaft really.
I'm starting to see more of the darker body material now, which isn't nearly so hydrophane. I'll take notes when I cut the next batch. I have a bunch of new rough I want to test before I list it.
Some of this material is so exotic, it has a form I call "egg" opal, where a center of yellow to amber opal forms with a shell of white or clear around it. Others are just the opposite, with white or clear centers and darker shells. The play of color seems to form its own structure without regard to the body color. This is some wild looking opal. There's a lot of the rectangular and triangular geometric forms too, some real interesting patterns.
Mike

[opalfireinfo]

this is the one that got scratched, it came out ok...

I dug out an old well worn 600 diamond disc and used oil to do some grinding and rough shaping today. It cuts way too slow for LR or Brazilian opal but this Ethiopian is like butter and even a dull knife works. Then I'm using my 1200 spool for final sanding. This way I never have to get the material wet.

Quite different from the material Paul describes in the initial post of this thread, this opal I'm cutting now and selling as rough here on the site does not have a high water content. That was from the older locations that I'm not seeing much of anymore. This new material is bone dry and should stay that way. The major seller who cuts his own Ethiopian here on site has talked about the long wait for the stones to dry out from the cutting process. He is a far more patient man than I.

There is a piece of equipment made by Graves called a spool polisher. When I was young, it was made with maplewood spools, now they use phenolic. It's waterless and uses diamond compound for 6 stages or so. Has anyone here ever used one? When I was young it cost $85 bucks, now it's $285. I've always wondered if they were any good.
I've used wooden laps and wheels dressed with diamond paste before, actually, that's what I used for this stone at the 1200 stage. I've used dowels and matchsticks in my flexshaft to hold diamond polish for carvings. Wood is a good medium for holding diamond compound.

The other problem I found was my dopping method. Didn't think ahead about the water problem. Wood glue soaks off real easily, IN WATER!!!
So I froze them, since wood glue says not to freeze it, and they came off, but not like popping off wax dops. The wood glue got kinda brittle and broke. Too scary for my old heart, so no more wood glue for dopping. I may go back to wax, but I'm looking at other things like tacky-stick stuff that holds my posters on the wall, or double sided tape, some of those are pretty strong.

It's always something...
Mike

Mike

[PinkDiamond]

Very nice, Mike! Looks lovely!! I'm not a cutter, but I know many cutters from other forums I'm on have said they dop with blue tack, or it could be blu tak or something weird like that, but I remember quite a few said they liked using it, and when I asked what it was, what they described was exactly what you mentioned; poster putty for attaching posters directly to the wall. Gemologists occasionally use it to hold gemstones over a light source, so hopefully it will work for you. Keep us 'posted' ...heh..., and again; nice opal!

[opalfireinfo]

Thanks, Pink. Sure is rewarding when they turn out nice.
I forgot to mention it is 9 mm x 13.5 mm x 4.5 mm and weighs 2.54 carats.
I'll list it soon and there'll be lots more pictures there.
Thanks,
Mike

[sedaopals]

WELO ROUGH OPAL I have been cutting this material since it frist came out in 2008 and i have some stones on the site here which are still good solid stones.Some cutters cut it dry but i always prefer wet cutting even though i have large industrial fans to suck out dust.I cut it similar to ridge material but im a bit softer with rubbing as it is a slightly softer stone.When wet some sample stones i tested incresed there weight by app 8 % a amazing amount.I have taken some stones in and out of water many times and it still hasnt cracked.I have also stated cutting doublets which come out interesting.While this is a new field it dosent have much history but i feel it has a good future.Some specimens i keep in a glass jar just to admire the beauty in the stone when it becomes transulant.Some cheap stones can look stunning in the domed gem glasses which magnifiy its stunning patterns.Have fun Paul Sedawie

[PinkDiamond]

Good to see you post, Paul. I was just trying to refer elflife8 to you for natural amethyst in the amethyst thread that's going, so check out that thread and show her some of the real stuff.