May 27 2009

Enameling on Hadar’s Clay™

My student Hayley Tsang and I prepared a few copper clay pieces for enameling, and I sent them to Thompson Enamel for testing. The assessment arrived today.

Bill Helwig, who tested the pieces, says that Hadar’s Clay™ can be enameled. Here is a piece he enameled. The piece was made by Hayley.

Mr. Helwig also explained why certain pieces that we sent were not likely to yield good results. The explanation is very detailed and professional so I won’t present it here. However, he offered some good advice that I would like to share with you. I would like to thank Mr. Helwig for taking the time to discuss this at such length and in such detail.

1. Metal clay is porous. The material should not be exposed to liquids.

2. Find ways to reduce porosity. Work the surface of the metal so that it is highly compressed, e.g., burnish, chase, planish, engrave, or tumble with steel needles. This will greatly improve the clarity of transparent enamel provided that the enamel was properly prepared and applied.

3. When designing a piece to be enameled:

a. The metal should be of uniform thickness
b. It should have an edge to stop the enamel
c. Depressed areas should be between 0.3 and 0.4 mm, nothing deeper
d. No undercuts

4. If the surface condition is not improved as described in #2 above, transparent enamel will never look very good, so use opaques or gold and silver foil.

These are pieces I played with. I told you I was no enameller!


May 25 2009

Creating an Alloy by Mixing Silver Clay and Copper Clay

Quite a few disasters happened when I fired copper and silver clay together. Here is an example:

What I think may have happened, is that the copper and silver created an alloy, and the hold temperature was too high for that alloy. When you alloy two metals, the melting temperature of the alloy will be lower than the melting point of each of the pure metals constituting the alloy. For example, fine silver melts at 1760°F; copper melts at 1980°F; but sterling silver (which is a combination of 92.5% fine silver and 7.5% copper) melts at 1640°F.

However, I was curious to see what kind of an alloy can be created by actually mixing copper clay and silver clay, wet, and firing them together. I mixed copper clay and low-shrinkage silver clay.

I rolled it 3 cards thick and cut a circle, ¾” in diameter.

I fired it with a batch of copper clay, making sure there were no bronze pieces in the box.

It blistered badly, so obviously the temperature was too high. The shrinkage was about a third.

Next, I sanded it as much as I could to see what color it was.

Here it is, next to copper and bronze.

And here it is next to copper and bronze painted with Baldwin’s Patina.

The ratio I used was 6 parts copper to 4 parts silver. Other combinations probably will yield other colors. Another thing that will require some experimentation is finding the right temperature for firing these alloys.

One question I ask myself is: is the difference in colors distinct enough to justify all the effort? Another question is: Wouldn’t it be possible to achieve the same colors at significantly lower cost by using combinations of copper and bronze?


May 17 2009

My Next Book

I have been working for some time now on my next book. My last two books featured a lot of pieces made by my local students, but now that I am corresponding with so many of you in different parts of the world, I feel that my next book should include your work as well.

Photos

If you want to take part in this book, please send me photos of your work. Unlike the Gallery section on my blog, the book requires photos in high resolution (300 dpi, at least 5” x 5”). If you don’t have the equipment to take the pictures yourself or the budget for a photographer, please send whatever photo you have. Then, if your work is accepted, you are welcome to send me your pieces for photographing. I promise to take good care of them. Please pack them carefully send them insured, and I will send them back insured.

You can send photos on a CD or email them directly to me. If you choose to email hi-res photo, please include each photo in a separate email.

Credit

If you send photographs, please include your name and location, title of the work, photographer’s name, size of the piece, techniques and materials used. The book is going to be brand free, like my first book on silver clay. No brands will be mentioned in the credit of the photos or elsewhere.

Requirements

The book will focus on mixed metal jewelry from metal clay (by “mixed” I mean combining different metals). The main requirements are that the metal part of the piece (except for findings and chain) is made from metal clay, and that the piece presents a combination of either copper and silver; copper and bronze; or copper, silver and bronze (the combination of silver and bronze has already been covered in my second book). Non-metal elements such as gemstones, enamel, beads and glass are welcome. Single-metal hollow forms from copper or bronze will also be considered.

The consideration of whether or not to include a certain piece in the book will be based on their relevance to the projects, available space, and quality of the photos. If your piece is not included, please do not regard it as a critique of your work.

As usual, the photos will appear alongside the projects, although I am also considering the possibility of adding a separate Gallery section. The credit line will include at least your name, the title of the piece, and the photographers name.

Submission Fee

Submission and photography (if required) are free of charge. However, since the number of copies is limited, I cannot promise free copies.

Deadline

If you feel that you don’t yet have something you want to show, there is still time. Since my book is self-published, I can be flexible with the deadline. It would be great to have all your photos by the end of August. If you have an idea and you find it hard to bring it to life, please feel free to consult with me. I will do my best to help. I hope to go to press by the end of the year.


May 13 2009

My Second Big Piece

Although not as big as the tile, the corset is 2″ x 2″ x 1″, and weighs 3 oz (90 grams). It was too tall to position horizontally in a 2½” tall steel box so I tilted it back about 45° and made sure it was full of carbon. Here is how it looked before firing:


May 8 2009

Instruction Manual for Hadar’s Clay™

In the right-hand pane, under Hadar’s Clay™ Metal Clay Powder – Copper and Bronze, you will find a link to download an Instruction Manual for Hadar’s Clay. This manual consolidates most of the information that has been posted here sporadically. The other, topic-specific files are still there, but have been updated. Below are some highlights from the manual and some new information.

Mixing the Clay

I have noticed how some of my students mix the clay. Sometimes a rolled layer from freshly mixed clay looks like this:

The white spots are grains of binder that have not comletely dissolved. If you see them, continue rolling the clay until they disappear.

Warping

Copper and bronze clay shrink about 10% while they are drying. That causes flat pieces to warp, even if you dry them in the air. Don’t leave flat pieces to dry unattended. You can safley dry them on a heating pan at 200-250°F (95-120°C). They will start to curve within seconds. Turn them over. They will soon start curving to the other side. Keep flipping them over until they stop. The whole process is very quick.

Alternativeley, once the top side has started to dry, tape it down to your drying surface.

Re-shaping

If pieces have already warped, you can wet them so they soften and can be flattened again under heavy objects. However, this is a messy procees. If you leave them in the refrigerator for half an hour, they will regain some flexibility, and you may not need to rehydrate them.

Shrinkage

Flat bronze clay pieces shrink about 25% after firing. Flat copper clay pieces shrink 15%.

Three-dimensional pieces shrink very little. Bronze shrinks a little more than copper, while both shrink less than low-shrinkage silver clay.

The diameter of the bronze circle above shrank from 20mm to 15mm, while the diameter of a copper piece shrank from 20mm to 17mm.

Pitting

Pitting (as opposed to blistering) is common, especially with bronze clay, and often on the back of pieces. It happens with copper as well, although at a higher temperature. The best way to avoid it is to fire all pieces, even flat ones, positioned vertically in the carbon.

The heavy bronze piece was fired with its back on the carbon. Note the carbon granules that got stuck in the pits. It seems that the softness of the metal when it’s hot, combined with the weight of the piece, caused the carbon granules to penetrate the back side. If pieces are fired vertically, weight is not an issue.

Blistering

Blistering refers to “bubbles” the sometimes show on the surface of the metal after it has been fired. It is caused by overheating, and will happen to bronze at a lower themperature than copper. If it happens consistency, you need to lower the hold temperature at the second phase of firing.

If the surface is not textured, these “blisters” can be eliminated by grinding them down with grinders or sanding bands, starting with 80 grit.

Repair

Silver clay is easy to repair. The fresh low-shrinkage clay applied to fired silver seems to stick pretty well. This is not the case with bronze and copper clay. Fresh clay doesn’t stick to fired metal, and if it does, once it’s dry it tends to separate and peel off.

Once you have finished applying the mending clay, don’t wait for it to dry. Stick it wet into the carbon. You don’t have to fire right away. The repair clay will stick just fine.

Out of curiosity, I cut copper and bronze clay circles and stuck them wet into the carbon, right before I started to fire. They came out just fine. Go figure!


May 2 2009

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