Design is a product of your creative imagination.  Objects of jewelry are the combination of design with a thorough knowledge of tools and materials.  You can't separate design from either your choice of materials or the procedure they dictate.  A thorough knowledge of the working characteristics and limitations of your material will help you make the right choices. Lost wax casting is a direct way to get into platinum and create a real product with limited resources.  Preparing wax for platinum takes a little extra care.

Wall thickness is critical.  Try to keep it as even as possible. 1 mm is recommended (thinner .5 mm or thicker up to 2 mm only for special areas or shanks.) Use a spring gauge to check wall thickness.  You can modify the tip to get a more accurate reading in tight or hard to reach places.

Detailing the Wax
The more work you do in wax models, the better.  If you're going to pave' or set stones, plot them on the wax with a pen, then drill and open the holes. It's easier to make changes in the wax.  The holes are a good window to the wall thickness and you can see how they line up on the inside.

Finishing the Wax
A fine steel wool is the best, inside and about spruing. Here are some general guidelines:

1. Sprues should be slightly heavier than the thickest part of the model.
2. Make them from round wire.
3. All the connections should be smooth and rounded.
4. Don't over sprue.
5. Connect at the thickest area for the best flow.
6. If you have multiple sprues going into your piece, tell your caster not to cut them off.

Don't let the caster cut the sprue!
It's a good idea to put a little reminder on those special models that can become distorted when sprues are removed with a pneumatic cutter. Leaving the sprues on gives you other advantages.  Sprues can make a good handle when filing or prepolishing.  Sawing them with 1 mm left on your piece gives you a view of the cross section. If there are air holes under the sprues, you can fill and repair, using some of the sprue to blend into the hole. Heavy sprues on shanks can be hammered into the piece to eliminate unseen air pockets, provided you back the piece on a ring mandrel, and then the sprue can be sawn off.

Distortion
Cutting sprues in your shop can distort castings.  If the piece has multi sprues, saw them off.  For pieces with no chance of distorting, a good flush cutter is the best.

Distorted castings can wreak havoc when many pieces are expected to fit and work together. Most distortion problems occur when wax is pulled from the mold. Once your caster is aware of this and becomes familiar with the actual piece, most of the problems will disappear. Also, don't plan on doing any complex work with the casting wax. Changing the model will be easier in the long run. Remember that wax, especially casting wax, becomes easily contaminated with dirt and filings.

Welding Platinum to Platinum
If you're building models that have many platinum parts that will be welded together, prepare the models with edges that can be used to supply the metal needed for the joint. Generally, using platinum castings over 30 mm long and 10 mm wide in normal production is pushing the limit for consistent, clean castings.  The smaller the better.

Torch Tips
Using the right size torch tip can avoid many puzzling and costly errors.  The #1 tip that came with your torch is fine for most soldering procedures. The #2 and #3 are great for annealing or larger soldering jobs where a broad softer flame is required. However, I find with many platinum procedures that I need a smaller, more intense flame. Make your own tip for welding and tight soldering procedures.

Platinum—to—platinum soldering is actually a fascinating experience.
Platinum soldering is easy, more so than any other combination of metals.  Almost everything you need to know is in the Platinum Guides. However, a few comments on preparation may be helpful.

1. Make a small container to hold each grade in a different covered container.
2. Keep the solder clean and separated from all other solders.
3. Don't cut the numbers off the solder.
4. Don't start cutting on the edge where the numbers are.
5. If you cut off more than you need, put it back in the right container.
6. If you don't know what grade the small flakes are, scrap them.
7. If a piece falls off and goes into the fourth dimension, find it. This goes for all solders. Stray pieces of solder can find their way onto the next job in the worst places.
8. If you roll out your solder to make it thinner, clean it thoroughly.

Metal—to—Metal Joints and Co—Casting Platinum and 18K
"Intimate contact" is the way Steven Kretchmer describes interlocking; it's a very visual reminder.  Let's look at how preparation can save your production.  At the temperatures that platinum and 18K bond, the soldered or co—casted crystals of the two metals never really lock.  This creates a situation where they can be torn apart at the seams if the seams are not interlocked. So, all joints, whether soldered or co—casted, must be interlocked.  Mitering parts to fit precisely together is essential. 18K yellow or white gold solder can be used for soldering platinum.  Generally, the higher the temperature, the better the bond.

Using Platinum Plate and Wire
The first thing to do is inspect the platinum plate or wire. The occurrence of major defects is rare. However, here are a few things to look for:

1. Make sure it matches the same quality and type that you're using for casting, i.e., 950 iridium plate, with 950 iridium castings, etc.
2. Inspect for defects, pinholes, color changes, cracks, folds, or bubbles on the surface.
3. Check the side of plate for separations.
4. Look for pitting, cracks or flakes in all wire.
5. Square wire can sometimes have folds at the edges.  If the round wire is not highly polished from draw plate, or has lines in it, send it back.

All of these precautions apply for the plate and wire you roll and draw yourself.  This brings me to the most talked about topic of all.  Everyone who has written or talked about platinum for any reason stresses the importance of cleanliness.

Contamination
It happens so easily and swiftly that everyone falls victim at some point. Once you experience this costly error, you're not likely to forget.  You should become fanatical.  Take every precaution and read the articles and manuals written about platinum.  Mostly, common sense and cost of materials will mandate good work habits or you'll go bankrupt.

Tool Related Problems
Most tool related problems can be easily avoided with good work habits an common sense.  The platinum guide book reviews and describes most of the tool requirements and purposes for platinum use. Here are a few things to look out for:

1. Bee's wax:  It works great as an all purpose lubricant, but it sits in the corner of your bench pin and collects particles from everything you use. Wash and steam the wax off before you heat, roll or draw your platinum.
2. Keep a soldering block exclusively for platinum.  Wash off dust or any old flakes of solder before starting a new job.
3. Remember at the temperature required to anneal, solder or weld platinum, all the normal jeweler's tools will melt into the hot platinum. This will happen quickly and show no mercy.  Tungsten carbide is the safest metal to use for a solder pick.
4. Tweezers: Make yourself a pair of platinum tip tweezers. It's less expensive than contamination by melting steel into your castings, plate or wire. If you break a tool, remove it immediately.  Soak the piece in an isolated bath of hot sparex or sulfuric acid.

There's one more procedure that can save a piece at the final hour.  Even if you've done everything right, you can still fall victim to an unforeseen pinhole.  Size up the hole to be filled, use a ball bur that will fit very tightly into the hole, and carefully open the hole so that the ball bur goes in completely. Undercut the edges of the hole with the same bur, and clean the hole of any wax or oil.  Prepare a tiny platinum bead the same size as the ball bur you used.  I perform this procedure on a charcoal block. Make a tiny dot in the charcoal with the bur to hold the bead and keep it round. The bead should be round and shiny.  Push the bead into the hole of your platinum piece. It should protrude just a little.  Take your hammer hand piece (set on "easy") and make sure the tip of your hammer is slightly rounded and polished, and hammer straight down, rotating around the edges of the hole. Don't over do it.

Pre—Polishing and Polishing
Pre—polishing and frequent inspection are the most important money—saving steps you can take.  If you look for problems before getting too for along in the work you can avoid 90% of the losses incurred from having to reject finished pieces. What does prefinish mean?  Look for this information in the Platinum Guide.  Here are a few reminders:

1. Inspect the castings, plate and wire.
2. Don't use rough 00 files; only use 4, 5, and 6, so as not to remove too much surface. The deeper you dig the more problems you're likely to uncover.
3. Don't use #3 sanding paper unless you need to remove a very rough surface.
4. #5 and #6 file marks can be removed easily starting with #1 sand paper then working up to 4/0 polish paper.
5. You can also go directly to a split lap from #5 files.  It's the quickest way to inspect the surface, removes the least amount of metal, and your polishing is 95% complete.
6. If you polish the platinum parts to the rouge stage, they won't tarnish during soldering. Also you can clearly see any defects and 99% of the time you'll have the same finish after the assembly and final polish.

Split Lapping
Split laps are felt wheels that have slits in them so the work can be seen through the wheel.  They show the surface of the metal better than any other procedure. Split lapping is a complex, highly skilled procedure.  It requires a great deal of time and effort to master.

Stone Fitting and Setting in Platinum
Fitting/setting is a highly specialized skill and far too complex to cover in any seminar. It takes years for a highly skilled person to master.  I can only offer a few guidelines and precautions:

1. Set the stones after all the high temperature procedures take place.
2. Final fitting of stones should be done by the person who's going to set them.
3. If you pre—fit stones in bezels make sure they fit tightly. Don't plan on hammering the bezel to make it meet the stone.
4. Platinum holds stones better than any other metal.  Fresh wire prongs hold better than cast prongs. Plan your model accordingly.
5. Plan your model so the stone culet doesn't go through the bottom.
6. If the stone touches anywhere on its bottom, it will never tighten and could break.

Summary
1. Design for your materials, (platinum, gold, stones, etc.)
2. Knowing how metals react to one another is essential to design.
3. Wall thickness is a critical issue in casting platinum.
4. Detailing and fine finishing in wax will save time and money with platinum castings.
5. Inspect your waxes; don't cast problems into your work; keep filings and dirt out. 
6. Sprues can be useful handles, also a source of metal for fixing pinholes.
7. Inspect castings, distortion can be disaster, be aware of the many ways this can happen.
8. Cutting sprues using a heavy cutter can distort castings. Saw them off.
9. You can modify any tool to suit your needs.
10.  Precise model making and interlocking platinum—to—gold joints is essential to successful production.
11.  Inspect plate and wire; don't take for granted that it's perfect.
12.  Contamination is the fastest way to lose money. It can happen at every stage of production.
13.  Don't over file your castings, the less you take off the better.
14.  Definitely learn to use a split lap, it's the fastest way to see surface problems and gives the best finish.

Nothing is impossible. You can make anything your creative imagination can think of.  Learning the basics is 90% of the process. Expect to make mistakes and have losses. Remember creative accomplishment is the best payoff.
 

V4N5

Potential Problems in Design and Fabricating Platinum
Michael Bondanza
Michael Bondanza Design

This is an abbreviated version of the original work. For full technical details, please consult the original paper.