The instructable is to make a 3-D hollow-form pendant for a necklace. We make the hollow form by coating a Completely Dry organic armature (Popcorn, in this example) with 8-12 layers of Precious Metal Clay (PMC) Paste.
When fired, the popcorn will burn away, leaving only the pure (99.9%) silver from the PMC in the shape of your popcorn kernel!
Jar of PMC3 (Precious Metal Clay) paste.
1 inch piece of Fine Silver wire (dead-soft).
Victory Wax (or cheese wax).
Shallow pan for water.
Metal measuring cup for melting wax.
A craft or ceramic kiln of some kind.
Small, smooth jawed pliers.
Wire cutter or scissors.
Brass brush for polishing.
A necklace, piece of ribbon, or leather cord.
...all will become clear...
Step 1: What is this Magic "PMC" Stuff?
This product became known as Precious Metal Clay (PMC).
After drying, the PMC is heated to the fusing temperature of the constituent metal. During this heating, the binder burns away, and the metal particles sinter together into solid metal.
We will be using a form of this product which is pre-prepared to a paste-like consistency.
Basic PMC Working Tips:
Its all about the moisture, PMC can dry out very quickly.
1) Plan ahead (have your tools at hand) before you open your jar of paste.
2 ) Water can be used used to moisten the clay and smooth the surface of your pendant.
3) Dried out PMC can be reconstituted with water and reused.
Step 2: Select the Popcorn Kernel for Your Masterpiece.
Sort through the kernels and find an interesting shape! This is the fun part! (Eat the rejects.)
Decide how you want the shape to hang.
We will suspend the pendant using a piece of fine silver wire inserted into the popcorn. Because the pendant will hang from a wire loop, it is important to consider where the finished pendant 's center of gravity will be. If there is more weight on one side than another, the pendant will slip on the loop (forward, backward or to either side) until the weight is equally distributed (whether we want it to or not).
Ideally, the wire used to hang the kernel on the necklace will intersect the kernel's center of gravity.
Step 3: Make a Loop with Your Fine Silver Wire.
If you break your pencil, or if you're using half-hard or hard fine silver wire, you may need to bend your wire around a small nail or other small, smooth, round object.
You will attach this loop (known as a "bail") to the kernel, later in step 8.
Step 4: Skewer Your Kernel!
Insert a small bamboo skewer halfway into the popcorn kernel.
This provides both a handle to hold the shape as we coat it. Also, when the bamboo burns away, it provides a vent hole to let any remaining moisture/steam/smoke out during firing.
Step 5: Check Your Wax for Compatiblity.
To solve this, we are going to coat the kernel with a thin layer of wax.
However, the type of wax is important. Standard paraffin (candle) wax is too hydrophobic (water repelling) for the PMC to adhere.
I use "victory wax" which is a sticky, brown, sculptor's wax.
If you know a sculptor, odds are she/he has a few pounds of the stuff around. If not, I'm told that many PMC artists use cheese wax. That is to say, the wax used to dip cheeses in to seal them (like BabyBel cheeses). Just buy some Gouda, Edam, or BabyBel, and save the wax when you eat the cheese!
An experiment to see if your wax will work: just dip a tiny amount of the wax you have into the PMC paste. If it sticks, you're good to go!
Step 6: Heat Your Wax in a Double Boiler
To avoid causing a fire, we are going to melt the wax in an improvised double boiler.
1) Put a pie pan with about 1/2 inch of water on a hot plate.
2) Place a measuring cup containing your wax into the water.
3) Turn on the hot plate to medium/medium high (on my hot plate, at least).
4) Wait patiently until the wax melts.
Why use a measuring cup? It gives enough depth to dip, but doesn't require a lot of wax to fill.
Step 7: Dip the Kernel in the Wax
IMPORTANT: The video below only appears to show the wax being melted directly on the hot plate.
Do not melt your wax directly on a hot plate! Use the double boiler described in the previous step!
I just didn't want to set a cup of hot wax on the counter. So I set it on the (cool) hot plate. That hot plate is not even turned on!
Step 8: Add the Bail
The PMC paste will fuse to the bail during firing, providing a solid connector for your pendant.
Step 9: Coat the Kernel in PMC Paste!
Try not to jostle the bail wire. However, do make sure you paint a little PMC where the wires cross to ensure it attaches to the finished piece.
I used a #8 flat, golden nylon bristle brush. However, any inexpensive, synthetic bristle, artist's brush would do fine.
Step 10: Dry Completely.
Let each PMC layer dry completely!
It will lose it's glossiness when completely dry. It will also be a lighter gray.
Step 11: Add Layers of PMC to Make It Stronger
You've already done one layer...so...only 7 more to go!
(Remember to let it dry completely between coats.)
And after the last coat, it looks like the main picture (below).
Step 12: Shorten the Skewer.
Step 13: Fire up the Kiln!
Place the pendant on a small pile of vermiculite on a kiln shelf. (See pics).
Then you put the kiln shelf in the kiln. (See pics).
Since there are several types of PMC, you should follow the firing instructions in the box, but I'll summarize the firing properties here.
- PMC+: Smaller Particle sizes, firing times range from 10-30 minutes at temps from 1470-1650, Shrinks 12-14%
- PMC3: Smallest Particles, firing times range from 10-30 minutes at temps from 1110-1250, Shrinks 10-12%
The minimum times are what's required to sinter the metal particles together. However, the longer times will yield a stronger end product. You stop seeing any improvements in strength after the maximum times.
There are several inexpensive options to fire PMC without using a kiln. They require a little finesse, however, and so will be covered in their own instructables!
Step 14: Take the Pendant Out of the Kiln.
Let the kiln cool down to 800 degrees F before removing your piece. If you take the kiln shelf out of the kiln and rest it on top, the piece will air-cool to a touchable temperature after a few minutes.
Remember: It is HOT! It will fry your fingers!
Step 15: Why is it White?
It's kind of ugly if you leave it white, so let's polish it with a fine (small wire) brass brush!
See the difference? Even while it's still being brushed!