Creating and Finishing a BACK

[lostwax]

Morning all..excellent thread
I have been working on Mintabie opal for a while now and one of the problems I'm having is actually getting enough thickness to actually do a decent back.
A lot of these rough pieces are only 4-6mm thick and have a thin seam of color (1-2mm)..usually between layers of black potch on one side and dull grey or potch the other.
Anyway what I find is the better color is near the black potch and I'm ending up with stones that are only 2-3mm thick with backs that are flat but still contain traces of sandy material.
I'm prepared to live with that because I fear trying to go any thinner will just cause heartache and add to my "inlay only" material

So I guess it comes down to what you're working with as to how good you want or can do the back of the stone.
In my case most of the stones will be going in titanium pendants with only a small hole in the back to show that the opal is a solid and not a doublet.

Which I guess brings up another topic...would you rather see the dirty back of a stone in a pendant or ring, or have it completely incased, and how do you tell if it's a doublet or solid?

Cheers

Sean

[Kookielee]

I read your post before I went to club last week. Then, after having worked on some boulder, I found a small piece of gem opal (not Mintabie) in the jar that had light gray on one side, and darker gray on the other. So I did what you said there, and cut the light off first, preparing the face. It did face up well enough too. I didn't have time to finish the stone that day, but I did take some photos of where it's at now...



This stone is 11.6 mm long, 6.75 wide, and at this point about 5.8 at the thickest part, with maybe 1mm of colour over most, thinner on one edge, and a thick spot at one corner. It started in the same shape, already a rub. I just removed the top light potch, and a little sand (not every spec yet). I was surprised to find colour at all on that edge I said was thin. You couldn't see it from the side at all. And I put a slight polish on the face, for the purpose of these photos. I'm not using water here.



The corner with the thick colour has sand and such that will probably mean I'll be cutting most of it off. Then there's that spec of sand near the bottom of the side, that will mean either I'll nip that corner off, or I'll make the stone thinner from the back. The back is not entirely parallel to the face yet, so some of that already has to come off to even it up. Then you have the dome - it won't be a high one, that's for sure. I'll probably just round the edges a bit, leaving most of the face almost flat. Final shape will either be a freeform/triangle, or teardrop, depending on how things turn out.

This is typical of many of the opals I cut, although many of them don't start out this thick. They come from different places and look different, but how I deal with them is about the same.

Now comes the constructive criticism part... Have I done it right so far? and are my plans along the lines of being right?


And your questions - they're good ones! If it's a solid, it's good that people can see that it is. There is a trust factor, and while you know you are honest, a buyer might not trust your word. What people at the club sometimes do is make a sort of partial bezel thing in silver. It's hard to put verbally... It's like the back is fully covered, but they only do partial sides, making sure there is enough to stabilize the stone in it's setting, but not covering all the way around. It's probably somewhat like leaving a small hole in the back, only it's on the sides instead. They pick more protected areas... A rectangle would expose a small portion of left and right, but top and bottom are covered. A triangle would cover the corners, leaving only a very small area on each side exposed. I don't know if that's good or bad, thinking of possible damage during wear, but that's what I've seen some do.

As long as I trust the seller, I would prefer to cover the whole thing but the face, for the stone's protection, that goes for sides and backs. And I couldn't give a stuff about a dirty back, as long as the front is good. So when I first start setting mine, that's what I'll do. If I ever start selling, that might make things a bit different, though.

[PinkDiamond]

Nice Janice! Looks great so far! I'm looking forward to seeing how this one comes out. Enjoy!!

[OpalFlash]

Hey Janice,

this stones remembers me at my first opal I grinded... same color, same shape...just a little bit more crystal like and not so dark. I did it like you and finished the back at last.
I think you have to get the corner a little bit smoother. First picture looks good but second pic of that side shows the thinner colorbar and that maybe why you didn't grind the side as round as the other side. It's very difficult to give advices just based of 2 photos.. but I think it would be better if you round the other corner as well.

I finished my first welo this weekend and not only the first welo... it's my first tearshape high dome one. Puh it's really hard to get an oval by hand with a dremel and its even harder to get a beautiful high dome by polishing it by hand but I did it!
I really hope that I can get the camera from my friend again to show you that stone. I'm a little bit proud of it and I looked at it for maybe 2hours now. Like a wacko. It's very funny to look at cause it is crystal clear like glass and cause of the high dome it magnifies everything underneath it and the color shows through the whole stone.

Greetz,
Steve

[PinkDiamond]

I know what you mean, Steve. I just got my first two Welos from Doug at TopShelfOpals, and they are absolutely mesmerizing, and once you start moving them and the light starts to play in them you just sit there turning them and can't pull yourself away. They're like... psychedelic, man! Must be what it's like to be on an acid trip!!

[OpalFlash]

Haha! That's true! I cannot speak about acid trips but once I was in Amsterdam for holiday and we tried out magic mushrooms and yap... that's it.
Flickering colorful experiences with moving floating colors everywhere... like sitting in a cube of crystal opal. I never did it again but now I'm fully on opal and it kicks.

My girlfriend likes opals aswell, but she doesn't have the addiction (thank god!). This weekend I stared at the welo in the kitchen light for about half an hour. Then I put it away... after watching TV for 10minutes I said "Erm.. I think I will look at this opal in my hobbyroom again" and she answered: "OMG! Be sure that it won't look different after 10 minutes. You're crazy!"
Nah... different lights, different color, different pleasure.
Sometimes I really think I'm sick... but hey... I'm not alone and that's great!

Sorry for going OFF-Topic... so back to the backs.

Greetz,
Steve

[Kookielee]

I have a few more photos, but I'm not sure if they'll be helpful, and I'm not sure if I'm understanding you correctly...try this...



Notice the spec still left in the colour bar (though colour isn't showing in this photo, you can see the line). I had to round the face some to get that sand out, and will still have to do something to get the spec. The left side is the deep colour section that has flaws. The right shows flaws that will have to be removed too, rounding that corner. So this triangle will end up with well rounded corners, if it ends up a triangle.

Originally, I didn't see the thin colour at all, and I was making the back more parallel to this thicker side, what I thought was going to be the face. When colour started showing up at the thin edge. it made the possible face bigger, so I quit grinding the back altogether, just to see what it would face up like including that thin section. Let's try this photo, maybe it'll show what I'm talking about



What appears to be purple in the bottom of this photo wasn't originally visible, only what appears to be blue. That blue was also visible around that corner to the edge that's now lying on the ground. At the top in this photo is the corner with the thin colour. As you see, work needs to be done on that corner, it will be rounded. Also, you can tell that the stone is thicker on this corner because I stopped grinding when the colour showed up on top.

I guess what I'm trying to demonstrate is that when I'm working with this lower quality opal, it's more a matter of dealing with original shape, colour bar, and flaws than a choice of thickness of stone and planned shape. I start grinding, deal with the many issues, and let the stone dictate to me what it would look best as. I try to imagine it beforehand, but nine times out of ten, something comes up, and it just doesn't work out as planned. Many times I've been pleasantly surprised, but then, sometimes I spoil the stone completely instead. I always try to get the biggest brightest face. The rest can be incidental, including a dirty back. I'm wondering if there is a better way, one that is a little less 'hit and miss' guesswork. Guesswork really is a good word to describe the way I feel when I'm dealing with gem opal at times. I figure most issues have a right and wrong, and if I learn the proper way to deal with each one, it'll take a lot of the guesswork away. Experience does too, I know...

And this stone demonstrates a typical way that I do things. Face first, at least in its early stages, then sides and back. Without using a dop stick, I can then polish back and front at the same time, and don't have to trim my fingernails for at least a week . Don't know if any of this is right, but it just seems to be the way it works out, for reasons just like with this stone.

I've tried a dremel too, and that's why I stick with the grinder. I can't do a dome with a dremel to save my life!

But there is hope for me... This is the kind of opal I'm better at...



Did this last week too...

[OpalFlash]

Hey Janice,

it's like you said and like I'm doing it aswell. With cheaper stuff you really have to follow the color, hoping that there comes no sand again or simply no color. I have some pieces in my desk where I followed the color... nice pieces but ugly shapes and thin material.

But even with the better rough stuff you have to check the bar very carefully before you can define the shape.
First I try to find out a shape where I can keep as much opal as possible (without any crack). After that I really stare into the opal trying to imagine what pattern it would be, what color will show up and then... as a third step I decide which shape would kick out the color at it's best.
Sometimes you have stones where you have to do it in a certain way, cause no other way would cut a stone.

At the beginning I didn't cut opals in different stones but now I see, that there is sometimes no other way to get out of sandy places or cracks without loosing too much. Sometimes I cut the opal right at the crack, so that both pieces don't have a crack anymore, but that's different with every stone.

Yap.. I'm ginding with a dremel and with my hands... I know what your speaking about with you nails. On Saturday I looked at my hands and started laughing cause it was like "bling bling" cause of the 2500grit and cerium oxide. Like having a manicure.


Greetz,
Steve

[starbird]

Hi Jenny,
Also Pink, Janice, Sean, Steve and Dien. As uaual I'm late to the Party!
This is a very interesting thread so I thought I'd chime in here. Since I started cutting at an early age and we all know bad habits are hard to change, especially when you think you know everything as a teenager and develope these techniques. I still do thing sometimes unconventially, but that's how I've done them for 40 or 50 years so just because I do them this way just means they have worked for me(or I wouldn't still be doing them) but that might not be the best way. (my disclaimer)
I always start with studying the piece trying to decide which direction the colorbar will face best. Next I try to determine where the colorbar runs and any changes in depth, brightness, colors Etc. If it's necessary to work the sides or Rub the top or any other area to expose an area to determine what the color does as a whole. I pay no attention to the other parts of the stone including the back, I haven't yet at this point determined the size or shape. After I've determined pretty much where I can obtain the best color and considering the largest yield. At this point if I have a particular area that will produce the best gem this rub will yield I study where I can possibly cut other gems from this same piece without sacrificing the original gem, also at this point I check to see if there is a possibility of a two sided stone keeping in mind the back side quite often won't be parrllel to the top if you chase another colorbar for the back or if the primary bar is thick enough to finisn also for the back.
After this study, remember I've just determined the approximate main color for the top, I "chase" the main color keeping several things in mind all at once, where the best color goes, any imperfections, sand, blanks(common opal) irregularities both good and bad. I stay just short of what I persieve to be the best color, sometimes grinding beautiful color down the drain to get to the "best" possible GEM.
As I'm shaping, cutting out "bad spots" accenting, if possible, watching the thickness and overall shape. This is the first time I seriously consider the shape of the top and the first time "START" thinking about the back.
Once I've worked out the final shape of the top, while I'm cutting, I take the top and down the sides 2 to 3 mm to a 14,000 finish, virtually complete.
Once that is done, if possible, I try to cut the rest of the stone, just mentally roughly 1/3 of the top face trying to keep a minimum of 2 to 3 mm., quite often if the colorbar is so gorgeous I'll take it down to " zero" and reset that side changing the overall shape and determine the overall shape with a minimum depth of that previous zero side trying to maintain at least 2mm. Then the finished shape has to be a graceful and pleasing shape.
I then finish the backside and any other rough areas I've exposed to 14,000, redop and refinish the top and any other surfaces I consider Gem to 50,000, giving the complete Gem at least 14,000 finish even if the bottom is left with discolorations, pits, sand, or other imperfections. If I have small imperfections in the finished face I will leave them if they're minimal and don't degrade the finished gem in the end. I photograph at maximum enlargement which magnifies these Imperfections and they are easy to see in the photos but if I've left them they are minimal and don't distract with the naked eye. If I get to the point where I could remove them without sacrificing the beauty of the finished gem then, of course, I totally remove them.
Keep in mind now I'm cutting rough that's set for decades and have already culled material with "issues" so what I'm cutting I don't have to worry if my working it is going to cause additional problems with cracking or crazing etc. to include possibly HOT DOPING 2, 3, 4 times. I very seldom have any rubs crack from heating for the dop and I dop extra hot, sometimes 2 to4 hours on the dop pot ledge. I increase the pot temp by making a dop lid out of a jar lid that I screw on a cabinet pull on the top and relieve cut one side enough to hold 12 to 15 dopsticks at a time, this also keeps the dust or anything else out of the wax pot, and I usually work 10 to 15 Gems at one time over about 1 1/2 days. This hotter dop requires me to introduce new, clean wax much more frequintly because the hotter temp scorches the wax after a while, sometimes removing and discarding dop wax every other week or so.
If I'm on a roll I can completely finish 10 Gems a day, but quite often a special gem will take me a week to finish. Each piece possess its own beauty that you are trying to discover and expose and you use whatever technique that individual gem requires. I've been known to study and manipulate all the scenarios I can think of, one special project for over 40 YEARS, others not unusual to study 1 to 2 years, good thing I've lived this long!!
Starbird

[Gemjunkie]

Holy cow, Chuck, I'll have to try to bid more on your opals.


Or just feel more guilty when I win one cheap.

[Gemjunkie]

OK, I definitely promise to fell more guilty.

[starbird]

Philip? Guilty??
Oh NO, I'm the guilty one, kuze thats pure HEAVEN!! What else could be that much fun, when you take a knoby or chunk of crystal thats full of mud and the more you clean or softly grind the skin and, alas! what emerges is this glorius color, gleaming and shining out like a headlight from this little ball of mud.
Earlier this evening I was sitting in my easy chair and my darling wife was in her spot about 12 feet across the family room and the only light was a 100 watt table lamp a couple of feet on my side table and the TV in the other direction about 12 feet, and I held up a piece of Hot Crystal and it shined clear across that 12 feet and she told me the colors she could see from there!!
Now how could you do that with any other Gem??
What do you mean Opaholic? Pure Heaven

[OpalFlash]

Hi and thank you for giving us the information of your way to do it. Ah... and welcome to the party!

Got the Camera back, so I will post some pics now. Get ready ^^

This is a Cooberpedy one...





It's difficult to catch the whole color in that stone. The flatter front part is stunning bright with fire from almost every angle. The higher part is 3D with 2 different colorbars inside. The colors are rolling through the whole back but not as bright as the front, but brighter than on the pics.
After rubbing the piece down I saw the shape and I though this is a funny one, so why bringing it into another shape? Looks little bit like a foot of an duck and the colorplay is just great.


Okey... here's my first high dome Welo one (sorry...no pics of the different phases):


It's so clear like glass and funny to watch. Cannot capture all the colors with photos. Try to make some videos of all stones soon to show you the colorplay. I'm poud of the shape, cause I did it freehand all the way and I wonder how I did it.
Look at the bottom... It's like I do it with slightly rounded corners again:



Okey...last but not least my stone I rubbed down yesterday. Puh I really don't know what to do with it, cause it seems that the color is brighter on flat surfaces that on the rounded top. On the other side it's a funny colorplay cause of the tip. The color rolls faster on the tip, than on the top... like a gearbox or something like that. Look at it:


That's the rough with water coverage to show how it would look like polished. It was totally dry before... I put it quickly into water and took the pictures fastly so that the water didn't cause the welo to change it state.


So bright red fire like an explosion. Just woow. But the top makes me nervous. I would like to have a proper grining machine where I can do kind of facetting. I think This stone would look gorgeous with this emerald fecetted shape.


Greetz,
Steve

[scribblygum]

Hi all,

I'm back from my holiday in Tasmania. It was really good....except there's no opal in Tassie.
They do have FAB crocoite though, and my son has a crocoite fetish. (you know crocoite is bright orange, thin, needle-like crystals, very rare and very exotic...found in only a few places in the world, the best of which is in Dundas, near Zeehan, Tasmania.) We bought some nice bits. I've no idea why.

Gee this thread is interesting. I'm glad I asked such a dumb question. I'm watching it all with interest and learning heaps. Those photos are FANTASTIC. Keep up the clicking cameras, a picture paints a thousand words. Chuck, what an interesting post. I'm learning heaps from you guys. I'm hoping now the kids have gone back to school I can get stuck into a bit of 'back - finishing practice!"

I might take some photos and you can all critique them. I'd rather be told what I wasn't doing well before too many are ruined. Still working on cheap stuff, but have also started some very pretty pieces given to me. I'm hoping they'll work out nicely.

[mehoose]

And you didn't drop in?