Tricks and Tips for Designing in CAD

As you see more and more of Brandy’s CAD (computer aided) designs in my shop, I thought it might be time to explain the design aspect of the process a bit more.  This will also help you if you are interested in placing a custom design order that requires CAD.

When do you need CAD?  CAD is extremely useful when you don’t want to make a design from scratch in metal, and especially when you have an idea that is more complicated, like my halo and multi-stone rings.  Imagine how long might take to make all those tiny little prong settings, for instance.  CAD is also useful when you have a specific stone and can’t find any stock settings that work.  But CAD doesn’t work well for flowy designs, and the geometry for certain shapes is incredibly complicated.  The more curves, ridges, settings, the more detail in other words, the longer it takes. 

Wedding Band CAD with Dimensions

A CAD ring will indeed take several hours in design work, or even more.  A simple setting might only be 30 minutes, but if you’re designing a complicated gallery for instance, adding all those curves and finalizing the dimensions can take an afternoon.  After that, the CAD model has to be “printed” in plastic , then cast in base metal, then molded, then again cast in the desired metal.  You can also go straight to casting from your plastic model, but if you then need another one, you have to print again, and printing can cost up to $100.  3D printers are expensive, and the printing process is slow.  Long story short, you are looking at a few hundred dollars before you so much as have a first casting.

Since CAD works on a mathematical basis, you need all your dimensions pretty well worked out before you can begin, and you may need to refine them as you design, or go back and forth with your CAD person.  This includes inside diameters of bezels, thickness of bezel walls, prongs, etc, for each part of your ring.  Brandy, who is very good at this, often supplies these after I give her the stone, or stone dimensions, the basic ring dimensions and my drawings.  She knows how deep a setting has to be to fit a stone, what wall thickness is required for a bezel, how much space to leave between stones, and other things you’d never think of if you haven’t done this a lot.  Nevertheless, sometimes Brandy and I have to sit together for a couple of hours and hash out specs as we try them out on the screen. 

This Cluster Ring is not Done Because We're Working on the Gallery , Often the Hardest Part

You also need to have a good sense of imagination, because a lot of time a model looks one way on the computer, another way when it is printed and cast.  One of my new rings ended up too heavy on the top, and the shanks were too thin to make it look balanced.  And when you plan to add stones in a beaded or burnished setting, you need to be able to visualize how the piece will look when it’s finished, because on the screen, and even in the silver casting, it will just be an empty canvas.

My Victorian Flower Earrings Before Setting

A Finished Design with the Same Setting

Sometimes other impracticalities intrude that you don’t think of.  Your finger is too small to support several stones in a row, or sizing will be an issue later.  Eternity bands have to be done for each size for instance, and in each case you have to change the design a little.  You also can’t just make a design bigger or smaller because you will want to shrink just certain aspects (i.e. the center setting but not the shank).  This means that certain changes in size necessitate many other changes down the line. 

               Finally, you have to think about practical aspects during casting and printing.  The ring I made (below) cannot be cast in one piece because the silicone could not get underneath the ring.  So Brandy made a gallery, lifted the top and made two designs that have to be assembled after casting.  Also, since you can’t cast in two metals at once, any two tone designs require two models that have to be fitted together and assembled.  

Shank is Too Narrow (The Thing on the Right is the Sprue)

Can't Mold in One Piece

Top is Too Thick, Needs a Galllery

Breaking an Apatite. Or: How Observation can Interfere with Experiment

So I had the brilliant idea of taking snapshots while my setter, Pierre, set an apatite into my new silver halo ring.  Dark blue sapphire outside, turquoise center, it was going to look fabulous.  Pierre has some very fancy setting equipment.  At his bench there is a huge microscope with very strong lighting that costs several thousand dollars, surrounded by lots of other smaller gadgets.  I guess you need that when you routinely set expensive gems.  Luckily, my apatite had only cost me about $20. 

Ring Inside Ring Holder

First, Pierre carefully clamped my ring into a ring holder, cushioning the outside of the shank with tissue so wouldn’t get marred.  The ring has to sit tight in order for the pressure from setting not to dislodge it.  Then Pierre separated the double prongs.  During casting, prongs that sit close together often have metal in between them, and it is cut apart with a separator disc.  Then the prongs are shaped into claws and the seat is drilled: that’s a little groove on the inside of each prong where the girdle of the gem will rest.  I like my gems set low, and the apatite fit perfectly into the opening.

Separating the Prongs

Unfortunately, the lighting of his microscope was so strong that my iPhone couldn’t cope, so I asked Pierre to lower it.  Which he promptly did, but not without mentioning that he could no longer really see what he was doing.  I should have taken that as a cue.

Having placed the apatite into the ring, Pierre proceeded to push the prongs over the gem with his metal bezel pusher.  

Pushing the Prongs over the Stone

As a final step, he rubber wheeled the prongs.  This means sanding them down with a soft rubber disc so that the places where he marred the metal with the bezel pusher – something which is unavoidable – are filed back out.  Normally this is the tricky step because you don’t want the rubber wheel to scratch the stone. 

Rubber Wheeling the Prongs

As it turned out, in this case, the moment during which the little apatite incurred major damage was minutes earlier.  It happened shortly after the light was turned off in order to accommodate my iPhone.  Ahem.  The third photo shows you approximately when Pierre chipped it. 

Long story short, my apatite didn’t live.  And now there’s a pretty tourmaline in the center of that same ring.  So that’s how it goes.  Apatite is risky business.  With a sapphire, this would probably not have happened.  But from now on, I’m not going to ask Pierre to work in the dark! J

Chip in Girdle on Right Next to Where the Prong Would have Been (Plus Scratches You Can't See)

Working with Cabochons and Rose Cuts

If you are used to working with only faceted stones, you’ll find that cabs and rose cuts are an entirely different animal.  Very little of what you know transfers over to the non-faceted gem world.  Cab pricing and weighs are different, they are judged on a different scale, and most commercial settings don’t work.

First, be aware that cabs and rose cuts are not usually clean gems.  The facet grade rough is – well – faceted, and cabs are the next grade down before rose cuts and then beads.  Cabochon material is therefore rarely as clean as faceted stones.   The quality often ranges from very good (near facet grade) to very poor (totally dead and opaque).  Obviously, I don’t recommend the latter.  Cabs don’t have brilliance either, rather, when set right, they glow, despite inclusions.  Cabs usually rank better in terms of glow than rose cuts because the facets of rose cuts don’t let the gem be as bright.  And of course the term “window” doesn’t apply because to not have window, you need back facets.  Technically, therefore, all cabs and rose cuts have window. 

Spinel Rose Cuts

When you buy cabochons, you can expect a lower per carat price than for faceted stones, but you also need to expect them to weigh more.  On average, cabochons weigh twice as much as faceted stones in the same size.  The exception are rose cuts, because they are flatter and the top facets remove extra weight.  The facets hide flaws, however, so your expectations of a rose cut should be lower than that of a cabochon.  Rose cuts usually weigh about the same as faceted stones.  Often, though, a high quality cab and a low quality faceted stones can come out the same in terms of price.

Finding the right setting for cabochons can be challenging.  Even calibrated stones often do not fit the settings that are fabricated for their size.  Many are too high so that the bezel wall doesn’t fold over right; or they are too low so that the stone vanishes under the bezel wall.  Yet others are slightly too big or too small – the latter applies to rose cuts in particular.  The smaller the cabochon, the more problematic it is if it doesn’t fit right.  So when you choose cabs, watch for high dome and low dome, as the terminology goes.  If you have a bezel already, bring it with you when you buy the stone and see how the stone looks in it. 

Round Commercial Bezels

Add to that, that many cabochons are not calibrated in the first place.  So you have to expect to be making the bezel by hand.  This is even more the case for rose cuts, which are often cut in irregular shapes, just following the natural lines of the material.  The expectation is that for either, you will make your own setting, or have it made. 

When I make bezels for cabs and rose cuts, I usually do a closed back.  I find that many gems look washed out when there is no metal behind them.  The light simply passes through them and that dulls the color.  The exception, for me, is when I channel set cabs for earrings, because then I like the light to pass through.  A ring or a necklace has your skin behind it at all times, and that doesn’t help the stone reflect out.  In earrings, that is not a concern.

Square and Oval Cabochons, Cabochon Bullet

Gemstone Etiquette 101: Ten Gem Buying Tips

Yes, there are rules when you buy gems.  And if you don’t know what they are, you can easily offend or, much to your disadvantage, drive up the price at which you buy.  These ten tips will save you some grief, and hopefully also some $$$ at your next gem buying spree.  Remember also that strict rules are established because it is easy to cheat in the gem business.  Trust, therefore, is everything.

1. Gems are priced by the parcel or individually.  Large and uneven parcels are the cheapest, small and well matched parcels cost more.  Individually priced gems cost the most.  If you have the time, you can save by selecting from parcels, but be sure to communicate that you intend to select by asking for per carat price for selection first (unless, that is, the trays are openly displayed for you to pick from them).  And yes, prices are usually quoted per carat.

2. You can ask for a loupe, most gem dealers carry them.  Check the table and back for scratches, and rest the stone between your index and middle fingers to look for window.  Move it away from the dealer’s light source to see how it looks under darker lighting conditions.  For expensive stones, ask if you can take the gem into standard daylight, i.e. near the window.  If you drop the stone, look at listen: don’t take your eye off it and listen to where it bounces and how often.  The little buggers have a way of vanishing.  And don’t leave the booth while the dealer is looking.  You dropped it, so you have to help him find it!  You may also have to pay for it.

3. Don’t give the store away: if you’re asked for your budget, hedge or say you don’t know yet.  If you’re asked to name your price, ask the dealer for his price instead.  Gem buying can be like playing poker, where you don’t show your hand.

4. If you like a stone, don’t jump up and down with joy, especially if you forgot to ask for the price ahead of time.  And if you hate the stone, don’t insult the merchandize by saying it is not good.  Dealers are proud of their inventory and can think you don’t know what you’re talking about (and just maybe, you actually don’t).  Just say “not for me."   

5. Bargaining is tricky.  Many prices are fixed.  But you can say that a gem is a little out of your budget or more than what you were hoping to spend.  Then let the dealer come down in price if he thinks he can, or wants to.  You could ask if there’s anything the dealer can do on the price.  Personally I don’t.  I just say it doesn’t work for me, that I might have trouble selling the merchandize at my markup.  Then it’s the dealer’s turn to see if he can make a better offer.

6.     If you can’t estimate weight by stone size, have each gem you are considering weighed and priced before you make your final choice.  I have seen hasty gem buyers annoy dealers by piling lots gems onto their selection trays to buy and then putting most of them back when they hit the scale.  This wastes considerable time and if the gem show is busy, other potential buyers have to wait for you.  It is best if you memorize some standard sizes and weights before you start shopping (you can use a diamond table and add 20-30% for extra weight and bulky cutting).  Or ask the dealer to estimate, many can do that very well by just looking at your tray.

7.      Not all treatments are identified, in fact, many gems are loose on trays or in bags and just have an ID tag that tells the dealer how to price the gems.  For emeralds, sapphires and rubies, always ask about treatment.  The word “natural” is not helpful in this context, since it is used to distinguish synthetic and lab created material from the genuine article.  So a natural gem can be treated.  Some gems are always treated (i.e. London blue topaz).  You should be familiar with some of the basic ways in which gems are treated, but you can always ask, “is it treated”?  This obligates the dealer to disclose.

8.      Neither a price quote nor the agreement to buy should be retracted.  That’s why it’s important that the dealer knows what he is quoting you and how many carats.  His (or her) quote is good once it is made.  When you agree to buy, that counts as a verbal contract.

9.      In the gem buying world, there are no refunds or exchanges unless they are agreed upon ahead of time.  Buyers can switch out gems and return a fake, or they can scratch a stone, i.e. by trying it in a setting, and then return it scratched.  Sellers protect themselves against this with strict no return policies.  If the seller knows and trusts you, you can memo out a stone, either against deposit or for free.  During this time you are fully responsible for the stone, and if you lose it, you have to pay for it.  If you do not return it within the agreed upon time period, you can lose the future privilege to memo out a gem.

10.   For good pricing and to establish trust, introduction by another buyer or gem dealer is helpful.  If someone sent you, mention their name.  You can also recommend someone, but remember not to recommend people you don’t trust or know, because if an expensive deal goes south after you have introduced the respective parties, you can get blamed. 

Selection of Trays at a Gem Show

What’s a Gem Show Like?

In one word: overwhelming.  I was at the Jeweler’s Association Summer show at the Javitt’s Convention Center last weekend.  I had a long list of things I needed and a smaller customer wish list.  I had a good night’s sleep and got there 5 minutes after they opened.  Eight hours later, I was completely wiped out. 

The show I went to is mainly for jewelry but the AGTA pavilion has about 50 gem and bead dealers whose stuff you can look at.  Some have their gems in little pre-boxed parcels, others have open trays for you to sift through and pick what you like.  Prices are usually on the trays, but it is good if you can estimate weights because otherwise you will be surprised about your tab when it all gets weighed out at the end.  You may do what so many do when they overspend: ask some of the gems to be put back.  Gem dealers are used to it but that doesn't mean they like it.

Selecting from Gem Trays

I buy a lot of boxed gems but I also spend a significant amount of time selecting individual or pieces from little bags and trays to match for earrings.  I spent 90 minutes in one booth and I didn’t even realize the time!  I also bought a bunch of beads.

The most interesting find for me, but not affordable at all, were the Paraiba tourmalines in the photo below.  The 3mm melees started at $1200/ct – my price!  More than diamonds.  Sapphire prices have gone up again, I bought more or less what was left at the price of February from the dealer I know that doesn’t change the old prices on his gem boxes.  I found some nice multi-color 5mm round Ceylon’s (heated) that I will put up on Etsy.  And some peachy colored Morganite, but heat treated as well. 

Paraiba Tourmalines

Prima gems had a ton of beads that were fun to look at, and some carved rough.  I found a few pieces of nice richly colored heated blue zircon with them and some top drilled beads that I will make into earrings with pearl cups.  All in all, the show was a success for me, but there were some things I couldn’t find: good emerald, nicer green sapphire, pink tourmaline.  The latter has about doubled in price since I looked last, so I’ll have to check with some dealers in the city and look through old parcels.  All tourmalines have gone up but the pinks especially.  

Prima Gem's Bead Table

Jaimeen, Sukrita and Geoff from Prima Gems

Precision Cuts: Are they For You?

If you are addicted to gems, you will soon find yourself getting attracted to precision cut gems – gems that have unusual shapes and more intriguing faceting patterns.  But setting gems like these is a whole other story. The cutter’s objective – bringing out the best of the gem – often conflicts with jewelry design and ease of setting.  So before you sink all your spare change (and then some) into a precision gem, keep these pointers in mind.

If you don't want to spend a ton of money having a custom setting made, you need to stick to shapes for which commercial settings are available. Prong settings are come in round, oval, square, marquis, pear, pear and emerald shape, as well as some baguettes. For other shapes you have to adapt an existing setting. Octagons and hexagons can go into round settings, cushions fit in into squares. Some rectangular cuts can fit into emerald settings. Prong settings are forgiving and can tolerate a fit that is not exact. Figure a tolerance level of .5mm, but buy the setting .5mm larger if you’re not sure. Undersized prong settings are often too shallow and the prongs will not fold over the stone.

Bezels have to fit precisely, with at best .01 mm to spare. There are no commercial bezels for rectangles or baguettes. Otherwise they are the same as prong. Cushions do not fit into any commercial bezels.

Also keep in mind that colored stones tend to be deeper in cut than diamonds because they are cut for color optimization. The deepest and bulkiest cut is step cut which is common for sapphires. They have a heavy belly, as we say. Portuguese cuts are also s bit bulkier. So you should ask about the depth of a stone if that is not listed. Most settings are made for brilliant cut stones. The depth of a brilliant cut is 65 per cent of the width and that’s the proportions for which most settings are made. For prong settings, this means you may need longer prongs. For bezels you need depth or else the stone sticks out the back once it is set.  Remember that for a ring, the back of the setting has to be rounded out, so you have to subtract a couple of mm.

Ouch - this will hurt

Another point to bear in mind is that girdle thickness is an issue for straight bezels with a pre cut bearing wall. The gem might "spill out" and the bezel walls will not fold. An alternative is to have the jeweler buy tube (which comes in round, square and oval), and saw off a piece in the right length to fit the overall depth of the stone, then drill the bearing wall.  But that means that the jeweler has to buy tube and cut it to size, which can cost more. 

Bezeling doesn't work well with a round stone has corners cut into the girdle. The only bezeling option is to cut all the corners into the bezel itself and then hope the pressure from setting doesn't bust the gem. But there are no pre-cut bezels for stones with corners except for princess and emerald (there certainly aren't any for octagons). Also, that kind of setting is beyond the expertise of most setters – it hardly ever comes up so nobody gets a chance to practice.  And you don’t want your gem to be the guinea pig.

Finally, bezel setting implies that more pressure is applied to the stone than in prong setting. Especially when the bezels are thick, because thick bezels are literally hammered around the stone with a miniscule “jack hammer.”   Many gems cannot handle that, especially when the bezel is gold, which is much harder than silver and requires even more pressure. Also, it is preferred that the gem doesn’t have corners.  Hammer setting emerald cuts, for instance, is extremely difficult. Princess cuts are nearly impossible. One wrong move and the corner chips or causes a crack that goes through the entire gem.  Some gems, i.e. tanzanite, can break straight through.

This bezel is for hammer setting, the side view is the same as the one above

In summary: think “prong setting”, avoid gems with corners, avoid setting soft stones in hard metals, and run with cuts for which there are existing settings. 

Amazing but at best a pear prong setting works (the wire will show because it's per shaped, not trillion)

This is gorgeous but it will only fit into an emerald cut or oval prong setting

Gemstone Underdogs: My Favorite Under-Appreciated Gems

I've been buying beads and gems for about six years now, not as long as other addicts, but I buy every week, and I buy direct.  I rarely buy online.  Living right outside NYC provides me with a lot of opportunity to touch stuff, to loupe it, to see how it feels and acts under different lighting conditions.  I have hardly seen everything, but I've seen a lot.  And I think there are still gems out there worth having that haven't gotten the attention they deserve.  Here's a short list.

My Favorite Gem Underdogs (in no particular order):

1. Chrysoberyl: this gem belongs with the family of alexandrite, but it is more durable with a hardness of 8.5 - which even beats corundum.  The yellow color is really pretty, with the nicest specimens being lemon yellow.  The browns are so-so.  When cut well, Chrysoberyl is very brilliant, crisp, and it is still reasonable in price.  I've seen them as low as $20/ct on the web for the smaller and more brown or very light yellow varieties.  But remember that even for Chryso's, the 1, 2 and 3 carat imply shifts in price.  The cat's eye chrysoberyl is also interesting, but in large sizes it is very expensive.  I prefer the faceted gems.  Right now much of Chrysoberyl comes from Tanzania and Sri Lanka.  I like the Tanzanian gems, which are usually brighter, less brown.

Chrysoberyl Lot, The Brown in the Corner is Sri Lankan, the Center is Tanzanian

2. Merelani Mint Garnet: some internet forums say it's just a "lesser" form of tsavorite, and the term "mint" is pure marketing to drive up the price.  False - and true.  The term "mint" for the color is new, and mint garnet is Tsavorite.  But: Merelani mints have to come from the Merelani mines.  I've seen other Tanzanian mints, and they're not as nice.  The Merelanis have no secondary yellow compared to standard light colored Tsavorite.  Right now Merelani mints and Tsavorites are priced about the same, with Tsavorite topping mints in the larger sizes.  Merelani mint production is insanely tiny, and most lighter Tsavorites don't even come close in terms of color, crispness, and beauty.  I'll take a mint anytime over a Tsav.  Tsavorite production is down as well, so I expect both of these to only go up in price as availability dwindles.  I don't think you can go wrong buying a nicer specimen for your collection.

Merelani Mint Garnet Mix, The Nicest is Center Front, 5.8mm, Portuguese Cut

3. Color Change Garnet: forget alexandrite.  Just totally forget about it.  Birthstones are decided by the American Jeweler's Association for marketing purposes!  Color change garnet - the nice, high quality stuff - has a better daytime color.  The most beautiful pieces come from Tanzania and they're a strong teal color (Madagascar is another origin but I prefer Tanzanian).  Some CC garnets are also forest green.  The ones with brown, peach and red daytime colors are less valuable.  Most CC garnets have complete color change to a strong reddish purple, whereas most alex on the market today has only a faint change.  Alexandrite is murkier in daytime color, probably because it is more included.  One carat of the nicer stuff can cost me $5000-10000, so there's obviously no room for markup.  And "Russian" alex is just lore.  That hasn't been produced in over 100 years and production was never high.  Lots of stones marketed as that are fake.  Meanwhile, you can get a 1-1.5 carat cc garnet for about $600-800 per carat (prices change every half carat).  CC garnet should be clean when you buy it, or very close to it, and try to avoid grey mask (lots of the larger stones have grey mask).  CC garnet larger than 1.5 carats is very rare.

Matched Pair Color Change Garnet, Tanzania

Color Change Garnet, Possibly Madagascar

Tanzanian Color Change Garnet Pair in Incandescent Light, the Color Change is Actually Stronger

4. Zircon: low zircon, high zircon... I've never heard that language used among gem dealers, so let's concentrate on what I think matters.  There are lots of origins, I'm not aware of one being better than another, except Cambodia for blues, but that production is finished or nearly finished as far as I know.  Zircon is clean, very sparkly, and the whites, peach, red, brown and honey colors are very reasonable.  I prefer white zircon over any other white stone except diamond.  In the smaller sizes, it might be $20-30 a carat retail. You can heat it at home (see my blog entry). Use the cooler browns and red tones to make peach or white, stay away from the honey colors, they fade back to honey over time.  The blues, today, are exclusively heated.  You have to find old material for unheated and most labs won't be able to tell you either way, they just assume heat.  Some blues fade over time but they can be reheated.  In terms of price, blue zircons cost more in the larger sizes, and the more saturated ocean blue tones are also pricey.  The lighter smaller, pieces are about as cheap as the other colors of zircon.  So anything under 1/2 carat shouldn't cost too much.  The rarest color zircon, as far as I know, is green, with chrome and forest greens being the most uncommon among the greens (most are olive or a light green).

Rare Green Zircon

I have other favorite stones that are not very expensive: sphene, kyanite and apatite are three of them.  But none are very durable (sphene is the best among this list), and they're hard to set.  Apatite can't be pickled, and I'd hesitate with ultrasonic.  Kyanite is liable to split in half lengthwise if the jeweler applies too much pressure folding the prongs (and he should apply pressure so the stone doesn't fall out!).  That limits the options of what can be done with these gems, and it means that if you wear them in jewelry or don't keep them separate in storage, they will chip and crack over time.  An unsuspecting jeweler who offers to clean your pieces might destroy them.