Mar 22 2015

New Ways of Working with White Bronze

White Bronze combines beautifully with other metal clays. Because of its low firing temperature I used to think that in order to do this, you had to fire the other metal first, then add White Bronze using a mechanical connection, and re-fire at the lower temperature. For example:

Bronze ring

Drum earrings

In the two pieces above (the ring is Friendly Brilliant Bronze and the earrings are Friendly Copper), the White Bronze is connected to itself around a tube. This is a mechanical connection and it is hard to tell if the White Bronze is actually fused to the other metals.

Recent experiments show that it actually is fused to them. The result is strong, non-brittle pieces, with two strong advantages:

  1. It’s hard to distinguish White Bronze color from silver
  2. White Bronze tarnishes less than any other metal, including silver

I fired pieces of bronze and copper first and just placed a layer of unfired White Bronze on top of each, with no mechanical connection. I always thought that there wasn’t enough pressure to make these two layers fuse. I was proven wrong! Here are some examples:

Full overlay of of White Bronze on Friendly Brilliant Bronze:

White Bronze on Friendly Bronze

Full overlay of White Bronze over Friendly Copper:

White Bronze over Friendly Copper

Partial overlay of White Bronze on Friendly Copper:

White Bronze on Friendly Copper

In the following example only the White Bronze shows on the front of the piece; the backing is Friendly Brilliant Bronze:

What about hollow forms? This pendant and donut were constructed with Friendly Brilliant Bronze. The fired pieces were fired and covered with White Bronze, then fired again.

Donut

And these earring are two-sided; only one side was covered with White Bronze:

So far, applying White Bronze to another metal with no mechanical connection works with all other clays except for steels (these will require a mechanical connection.

The Process

  1. The backing layer (in a flat piece) or the core (in a hollow form) is 3-cards thick.
  2. Fire the pieces to the maximum temperature required for the specific clay. If distortion occurs, hammer or bend the pieces into shape.
  3. Add a 3-card layer of White Bronze. Make sure the White Bronze is connected to the fired metal at every point of its surface area.
  4. This is important: Let the the White Bronze overlay dry naturally or it will come off the backing layer. If you need to remove it in order to file or sand holes, as in the earrings shown above, wet the back of the overlay and press it into the backing layer. Then let it dry naturally. The White Bronze layer should be well bonded with the backing layer before going into the kiln.
  5. Fire for 2 hours at 1330°F in a brick kiln, 1380°F in a muffle kiln.

(True, this temperature is way higher than the firing temperature of White Bronze alone. However, bear in mind that the first metal used acts like a heat sink; it draws the heat away from the White Bronze, and this is why it is not over-fired.)

A few more interesting results:

Folded

The core of this hollow form is Friendly Brilliant Bronze. Two sides of the forms are covered with White Bronze, and the third side with a mokume gane layer of White Bronze and Pearl Grey Steel. It seems that this tricky combination is facilitated by the bronze backing.

Solid

And this one is still experimental: it is a solid piece of mokume gane made with Friendly Copper and White Bronze, with no backing layer or core.


Mar 11 2015

Making It Simpler

It has come to my attention, through email and the Hadar’s Clay Users’ Discussion Forum, that there is some confusion regarding the products on our store and the firing process. I would like to clarify these issues, especially for new users who may be less familiar with the history of the clays.

The Clays

Let’s start with the products. True, there are many clays to choose from. I remember the first time I came into a ceramic store and was overwhelmed by the variety of clays, under glazes, glazes and stains. I didn’t even know what to ask. Luckily, the case with our store is a little simpler. Almost half the clays consist of an earlier version, which personally I don’t use anymore.

You may ask: Why aren’t they just discontinued? This is simply out of respect and consideration for customers who still want them. I can absolutely relate to people who want that product which works best for them. I don’t ask why, and it not my place to change their mind. If and when these clays are no longer in demand, they will be discontinued.

These are the “older” clays:

  • Quick-fire Copper
  • Quick-fire Bronze
  • Quick-fire Brilliant Bronze
  • Quick-fire Rose Bronze
  • Quick-fire Bronze XT
  • Smart Bronze
  • Quick-fire Steel

The Traditional/Flex Clays are specialty clays intended for making flexible clay. They are not recommended for beginners.

All the clays mentioned above require a 2-phase firing schedule, with a cooling phase between phases. The first disadvantage is the long firing schedule. The second disadvantage is that there is a high rate of cracking with these clays. This is due the the cooling phase; the clays go through temperature changes before they are strong enough to withstand them.

The clays of the new formula were intended to overcome these disadvantages. The firing schedule involves one phase only and cracks rarely occur. These are the clays:

  • Friendly Copper
  • Friendly Bronze
  • Friendly Brilliant Bronze (closer to gold color)
  • Friendly Rose Bronze (more pink than copper)
  • Champagne Bronze (pale yellow)
  • Dark Champagne Bronze (slightly darker and deeper than Friendly Bronze)
  • White Bronze (silver color but brittle)
  • White Satin (silver color and strong)
  • Low-shrinkage Steel XT
  • Pearl Grey Steel (the only steel clay to be used on mokume gane)

The Firing Schedules

For each of the newly-formulated clays you can find an instruction manual in the right-hand pane of my blog. Each of them is fired at a different temperature but the firing process is basically the same. The most common problem in firing metal clay is crumbling after firing. This is mostly due to poor binder burnout. To overcome this problem, here is my suggested schedule:

  • Ramp at 1800°F per hour to 1000°F (in a brick kiln) or 1100°F (in a muffle kiln)
  • Hold between 1:00 – 2:00 hours. This is the temperature at which the binder burns up. The longer you hold at this temperature, the better. Bigger pieces or multiple pieces need longer hold time but I rarely hold for more than 2:00 hours. Holding 2 hours for small pieces doesn’t hurt.
  • Ramp at 1800F to the goal temperature for the clay.
  • Hold two hours.

This firing schedule takes 4-5 hours.

There are, of course, exceptions and complications. For example, when you want to fire more than one metal in one piece. Some of these issues are discussed in the Instruction Manual and some in my books. But for now, I hope this posting is helpful as a starting point. As usual, you can always reach me by email or use the Hadar’s Clay Users’ Discussion Forum and Hadar’s Clay Accredited Teachers for any questions you have.


Mar 5 2015

Adjustable Rings from Metal Clay – Yes, No?

Yes! I’ve been often asked if the metal is somewhat workable after firing, and wanting to be better safe than sorry, I’ve always said “No, do all fabrication before firing!” I still do all my fabrication before firing, but I also want to have the fired pieces be a little adjustable. What if a ring, for example, doesn’t come out the size I intended it to be? As you may have noticed, many factors can affect the shrinkage of a ring, including size, thickness, firing schedule, and firing environment (what else is in the kiln).

So I experimented with a a few open rings.

Rings open

Two of them are Friendly Brilliant Bronze, one Friendly Copper and one Pearl Grey Steel. The copper one is 6 cards thick; the rest are 4. All rings distorted significantly during firing. They were all hammered into shape over the mandrel, with no cracking. They were then closed with two fingers.

Bronze Rings overlapping

Copper and steel closed

To re-open them I needed to use the mandrel. The hardest to re-open was the copper (the 6-card-thick one). So far they have been opened and closed a few times without reaching the point of metal fatigue.

Friendly Brilliant Bronze was fired according to its regular schedule, with 1:30 hours hold at 1000°F. The copper and steel rings (I made a few of each) kept breaking until I raised the temperature to 1850°F (my kiln is brick, so that means 1900°F in a muffle kiln).

Just to see what would happen, I fired copper and Pearl Grey Steel at 1900°F (brick). They came out fine, although harder to bend. You may ask if this temperature is not too close to the melting point of copper. The answer is no, since the temperature displayed on the controller is always higher than that inside the carbon.

I am now firing both copper and PG Steel at 1950°F. Will report back.

That brings us to cuff bracelets.

Cuff open

Cuff closed

On hand

This one was made with Friendly Brilliant Bronze, 6 cards thick, and weighs 35 grams. It was opened and closed a few times in order to slide it over my arm. I am currently working on an open copper bracelet. A test firing showed that the copper bracelet, when fired at the right temperature, can be opened and closed and the open parts can be moved up and down.

In the kiln now: Low-shrinkage Steel XT ring at 1950°F. At a lower temperature Low-shrinkage Steel XT cracked when bent. I still need to test a few other clays. Stay tuned!