Casting

[1dave]

Casting Is well covered in Sharr Choate's book.



Index:
Partial Melt, Water etc. Casting, Carving Cuttlefish etc. - Here.
Centrifuge Casting
Sand Casting
Sandcasting the JB Way
Sling Casting
Steam Casting
Vacuum Casting


Buying Gold & Silver



Gold, Silver, Brass, Bronze, lead, solder, make it easy on yourself! You can make some fantastic pieces very simply.
I suggest you start with aluminum or brass because it is easy and inexpensive. When you are sure of yourself then move up to the expensive stuff.

1. Arrange scraps of metal in an interesting pattern, heat until it just begins to melt together, and STOP!



Those partial melts may be just the thing to use in fabricating a splendid piece of jewelry!

Continue heating with various sized pieces of scrap and they will turn into spheres, again Stop.
Those spheres can be used in so many designs.

Or continue heating and the spheres will flatten out. If on a carved mold, the metal can be hand pressed
- uh, use a fire brick or wet piece of wood, not your hand - into the mold.

2. Or continue to melt your metal, then pour it into a pail of cold water. The drops will form amazing shapes.



That can then be used in fabrication.



Dripping melted silver into water, ice, wet pine needles pine cones, or broom straws provide interesting shapes to work with! I always used a wet whisk broom. It still seems like a better idea.





3. mold casting - Using an old board can be a good beginning. Carve a form first, char it, refine it, melt your metal on it, then use another (wet) board to mash the hot metal flat. Try making belt buckles this way!

Cuttlefish casting -






4. Vacuum Casting - Don't toss that empty propane tank!



Open the valve all the way and heat that tank to drive all the gas out. Do it several times, then close the valve while still HOT! When it cools down, you will be the proud owner of a vacuum casting unit!
Make your mold with a hole in the bottom the nozzle will fit in, Burn out the wax, melt metal on top of the mold, then stick the nozzle in place and open the valve. The vacuum will help suck the molten metal down into the mold.

5. Sand Casting -

6. Sling Casting - I would never try this with gold.



7. Steam Casting - steamcast.blogspot.com/


8. For Lost Wax Casting you will need a centrifuge and metal wash tub to keep gold from flying everywhere!



I make my forms out of copper pipe to fill with cristobalite and my wax mold, but you will need to purchase Crucibles to melt your metal in:

[1dave]

Nov 11, 2013 12:21:49 GMT -5 1dave said:

Nov 10, 2013 22:15:37 GMT -5 gemfeller said:

Sounds like a twist on traditional Navajo tufa casting. I recall reading ads for this long ago in LJ but could never quite understand what made it "different." Maybe you can explain?

Rick

Tufa = limestone, travertine; but Eric Begay wrote:

Tufa stone is a volcanic, pourous stone that is found naturally in the area of the Navajo Reservation. The stone is very soft and can be scratch with a piece of metal. Although the stone is never heated, it works great at these high temperature.

So it sounds to me more like pumice.

Navajo artists took two chunks and rubbed them together until both pieces fit well together, then carved a pattern into both pieces with an opening at the top, heated the cavity, then poured molten silver into it.

ebegay.com/mm5/merchant.mvc?Screen=TUFA

Making do with what you had instead of buying $50,000 worth of equipment must have been a plus.

I think it would be a great way to make a belt buckle or bracelet.

[1dave]

Nov 11, 2013 14:22:47 GMT -5 gemfeller said:

Nov 11, 2013 12:21:49 GMT -5 1dave said:

Tufa = limestone, travertine; but Eric Begay wrote:

Tufa stone is a volcanic, pourous stone that is found naturally in the area of the Navajo Reservation. The stone is very soft and can be scratch with a piece of metal. Although the stone is never heated, it works great at these high temperature.

So it sounds to me more like pumice.

I believe the word "tufa" in common use for that casting technique is a misnomer. The porous volcanic stone used by the Navajos is probably tuff, compressed volcanic ash, not limestone. I cast some silver pieces using that method years ago and -- if I recall correctly -- the material was tuff which is basically tiny shards of wind-borne volcanic glass that's been solidified as sediment.

My original question was how does the garnet technique differ from tufa casting? What does the garnet sand do? How does it improve the process?

Rick [/quote]

[1dave]

Nov 11, 2013 14:35:27 GMT -5 1dave said:

Nov 11, 2013 14:22:47 GMT -5 gemfeller said:

Tufa = limestone, travertine; but Eric Begay wrote:
So it sounds to me more like pumice.

I believe the word "tufa" in common use for that casting technique is a misnomer. The porous volcanic stone used by the Navajos is probably tuff, compressed volcanic ash, not limestone. I cast some silver pieces using that method years ago and -- if I recall correctly -- the material was tuff which is basically tiny shards of wind-borne volcanic glass that's been solidified as sediment.

My original question was how does the garnet technique differ from tufa casting? What does the garnet sand do? How does it improve the process?

Rick

Ah, I thought you were asking about the Tufa.

I'm sure you are right about Tuff!

The garnet has a reducing effect like working on charcoal so there isn't so much of a fire scale problem.

Dave
[/quote]

[1dave]

Combining casting and fabricating, you can make spectacular showcases for your stones.

[1dave]

On page 208 of her Casting book, Sharr listed the stones that can withstand being cast in metal.
Of course the lower the melting temperature of the metal, the longer the list would be.

She states the high end of the Mohs scale of hardness helps identify stones to test before actual attempts.
They are:

8 - emerald, spinel, topaz

8 1/2 - chrysoberyl

9 - corundum, sapphire, ruby, titanium

10 - diamond

Although the stone should have a hardness of at least 8 on the Mohs scale, some gemstones with hardness between 6-7 1/2 may stand up without damage during casting, such as:

6 - zircon (low type), rutile, turquoise, feldspar, sodalite, lapis lazuli, prehnite, zoisite (thulite)

6 1/2 - nephrite, pyrite, epidote, idocrase, andradite garnet, olivine, hematite, benitoite, amazonite, marcasite

7 - agate, amethyst, quartz, spodumene, chalcedony, jadeite, tourmaline, bloodstone

7 1/4 - zircon (high type), pyrope and spessartite garnet

7 1/2 - andalusite, almandine garnet, beryl, staurolite

[Tom]

Great info Dave, thanks

[jamesp]

If we ever have to resort to guerrilla warfare i am coming to be under your command Dave.

i think you could put together some delightful gifts for the opposition.

Woe to the opposition, we are equipped with Dave's tactical do dads.

Those melt blobs are a great idea in the Sci Fi jewelry arena and free form jewelry. How can you go wrong with iridescent blobs of rich colored metals.

I never knew you could do castings w/budget home made equipment.

[bsky4463]

Great info - I am way intrigued with the blob castings...so many cool freaky possibilities.

[1dave]

I was just informed by pauls of this forum aimed at casting metals.

Alloy Avenue

[bentiron]

A little side note on tufa casting, always make sure your mold is dried out or you will have an experience similar to Mount Etna! Put in the oven at 150F for an hour to drive off all ambient moisture that will have collected in the stone, it is somewhat porous and does tend to absorb moisture. Be safe, molten silver leave some nasty scars.

[bobby1]

Sharr Choate's books were my bibles when I was starting out. She was a fascinating person to talk to. She was a member of the first club that I belonged to. I met a guy that worked at the same company as her (an early electronics company in the Bay Area) and he said she came to work dead tired from staying up most of the night working on those books.
Bob

[gemfeller]

Has anyone posted about steam casting? I seem to recall a discussion about it somewhere but I can't find it here. It's a cheap method of learning precious metals casting and good results can be obtained with it. I cast this gold ring with steam:



My equipment consisted of a short piece of broom handle, a big jar lid, wet newspaper, a terra-cotta flower pot, aluminum foil, modeling clay, an old electric hotplate, a sturdy tin can, some specially-shaped wax sprues, a commercial wax pattern, casting investment powder and of course the metal and a torch to melt it with.

Here's a great, detailed tutorial by Don Norris:

www.myheap.com/chapter-10-steam-casting/steam-casting-lessons.html?showall=1

[1dave]

Thanks Rick! Steam Casting - an easy start for beginners!



As water turns to steam it can expand up to 2,000 times it's original volume, easily producing enough pressure to force the metal down into your mold.

Building The Caster

1. Cut a 6 inch piece off an old broom handle or any other old round handle that you might have around the house, or buy a 1 inch diameter dowel rod from the hardware store and cut off 6 inches of that. This is the handle for your steam caster.

2. Drill a small 1/8 inch hole in the center of the cut (flat) end. Be careful drilling this hole. The use of a vise to hold the handle would be good, but if you do not have a vise use a c-clamp to hold it down to a table while you drill it. If you do not have a c-clamp, have a real trusting friend (and I find that getting them drunk first is helpful) to hold it for you. Really, it is not that dangerous, but caution should be used so that the dowel does not begin spinning during the drilling process.

3. Drill or punch a hole into the center of the empty tuna can bottom. Put the #10 by one inch sheet metal screw through this hole so that it is sticking out the bottom of the can. The head of the screw is in the can.

4. Screw the can on to the end of the dowel. The hole that you drilled into the handle will keep it from splitting. Be sure to tighten the screw.

5. Tear up three paper towels into approximately 2 inch pieces. Soak these in water and pack them into the can. Pack them in as tightly as possible. (You can even use another can that is slightly smaller than the tuna can to help you pack it tightly. Just pack the paper towels in to the tuna can, then turn it over and press it down on the smaller can until no more water can be squeezed out.) It is important that no more water can drip out of the caster.

The paper towels should be damp now, not soaked and dripping.

[pghram]

gemfeller, beautiful ring!

Rich

[gemfeller]

Thanks Rich. I only posted the image to illustrate that steam casting can produce worthwhile results. It's an inexpensive way to learn casting fundamentals.

[ol3m3]

For lots of information on homemade equipment go to the Lost Wax Jewelry Casting group at yahoo.com.

One of the suggestions to get into casting on the cheap is to do vacuum casting, can set up a basic casting table using an old refrigerator compressor, select one that has had the refrigerant removed but still works, can use the table for both casting, and for vacuuming the investment compound. go to the photo section of the group for lots of suggestions on vacuum tables and vacum chambers for vacuuming the investment compound.

Other then the vacuum table you will need a small kiln capable of going to approx 1400 deg F. to calcine the invested flask driving off the free and chemical water in the investment. also needed a torch of some type capable of melting silver and a pouring crucible.

As always can not recommend any of the information in the casting group, you need to use a lot of common sense, and do your research.

OM

[gemfeller]

Lost wax casting is often maligned because some people think it's a simple way to duplicate existing designs. That's true to a degree but it's also one of the most challenging creative arts when original designs are made from wax to showcase specific stones. Like settings fabricated from wire and sheet, original cast waxes are truly difficult one-off designs (unless someone makes a mold to reproduce them), which can be done with all designs no matter how they were originally made.

As an opal and fire agate addict I've always cut freeform stones. I've refused to cut standard ovals, etc. in those materials because nature made them in lovely, unique ways. They "tell" the cutter what they want to be when they're released from the rock that entraps them. My object is to showcase them as best I can in precious metals to let them do their stylin' and struttin'.

Here are some attempts to do that with fire agate and precious opal:

[bentiron]

Gemfeller, Nice to see you posting over here too. I don't think I've seen these before, very nice work, well done. I may need to dig my casting gear out and buy new coils for my burnout oven. They have then down at the ceramic supply house. Summer is not the best time here to do burn out as the electric rates go way up except at night after 9pm till 9am and I don't like to let them bake when I'm not awake.
You sure do nice work with that fire agate and opal.

[gemfeller]

Thanks for your nice comments bentiron. It's good to see you here. I no longer use my electric burn-out oven much. The power company has hiked rates so high here in California I can't afford to use it for single flasks. If I was doing production casting I'd go to a gas-fired oven. As it is I'm able to piggy-back burn-outs with a jeweler friend who does multiple flasks at a time in his gas oven.

When I do use it I'm fortunate to have found an old Rey Therminder that can be programmed for overnight use and holds the flasks at casting temp in the morning. Using it I sleep pretty well. I'm anxious to make more one-off waxes for special stones but life has a way of forcing me to do boring stuff instead of the things I'd like to do.