Why Fired Silver Looks Like Chalk

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Fresh out of Kiln sq


You may have noticed that when you bring your piece out of the kiln or from under the torch, it looks like chalk. It is white and has a matte finish. Why is that? It then becomes an amazing thing to watch this “chalk” turn to silver when you brass brush it.

The silver molecules on the surface of your creation form crystal-like towers. These are similar to tall standing and some downed trees in a dense forest. When ambient light comes in to these tower-like trees, the light is trapped. And none of it then reflects or bounces off and into your eyes. 

Light Reflecting Not

Light is trapped in the “towers and trees” of silver molecules.

When you brass brush the silver, the towers and trees are flattened along the surface. Then when ambient light comes in, it is not trapped and therefore reflects or bounces off and into your eyes. Highly compressed and polished silver reflects 95% of the visible light spectrum.

Light Reflecting

“Towers and trees” of silver are compressed. Light reflects off the more smooth surface.

Brass Brush

Brass brush . . . the first step in compressing surface silver



Here are more tools and processes that further compress your silver. The more the surface is compressed, the more reflective or shiny the piece or an area becomes.


Hammering

Heat softens silver, which is called annealing. Hammering makes silver stronger, again by compressing molecules closer and closer together. Try it. Take a piece of silver wire and bend it to get a feel for how easily, or not, it bends. Then hammer the same wire, not hard as to flatten it but hard enough so that it takes on some surface dents. Now bend it again. You hopefully noticed it was harder and not so easy to bend. (Equally, you could heat it and then do the bend test to see how annealing softens it.)

Hammers

By the way, a soft hammer, such as a rubber mallet, does not compress the silver.

Rubber Mallet


Tumbling

Tumbling a metal-clay piece in steel shot with tumbling solution is like hammering it with thousands and thousands of tiny hammers. Each tiny hammer or each bit of steel shot hits the surface of your piece and compresses that surface more and more. If you compare a pieced tumbled for 30 minutes with one tumbled for 3 hours, the difference in the final shine is quite apparent. 

Rotary tumblers tend to offer a softer tumble and therefore require more tumbling time than a vibratory tumbler. The less tumbling solution one uses, the more compression results. The purpose of the tumbling solution is to disperse grit (patina), heat, and to further treat the silver to prevent tarnishing.

Tumbler Lortone rotary

Rotary Tumber

Tumbler Gyroc-B Tumbler

Vibratory Tumbler

Steel Shot

Steel Shot in mixed Shapes

Burnishing Compound

Notice the name? BURNISHING Compound


Burnishing

Burnishing is taking anything harder than silver and pressing it against the silver. Hard. This pinpoint pressure compresses the surface silver in a small area. As you know, burnishing works on edges and high points and does not do well on large, flat surfaces. Why? Because you can see every stroke of the burnisher. 

Burnishing tools are most often agate (yes, it is harder than silver) and steel. You can use anything steel. Some of my favorite burnishers are kitchen utensils.

Burnisher Agate

Agate Burnisher

Burnisher Steel

Steel Burnisher

Burnishers unusual

If you know the purpose of this kitchen utensil, then you are at least 70 years old.


Polishing

Some polishing tools used on a Dremel or Flexible Shaft not only polish by removing a surface layer, they also compress the remaining surface layer.

Additional pressure when using a finer silicone polishing wheel slightly compresses the surface of the silver.


Soldering

If you have tried to solder a finished silver-metal-clay piece, you may have noticed the solder seems to disappear. It does! It flows into the pores of the metal clay. It flows, not between the surface trees of silver; rather, solder flows into the porous depths of the silver. Metal-clay silver is way more porous (and thus brittle) than manufactured silver.

What to do? Burnish the area that you will be soldering. Burnishing not only knocks down the trees of silver, it compresses the silver into itself, thereby diminishing and closing the pores in the silver.

Balling casting grain 4

Don’t be fooled. I am not soldering here — despite the solder block, solder pick, and torch. I was melting silver into casting grains.


For online courses in metal clay, go to I Love Silver, where you learn how to design and create your own silver creations.

© Kris A Kramer 2017