Working the Egg: Oxidize Silver without the Chemicals (or the stench of liver of sulfur)

By Anna on July 11, 2007 at 9:54 am


This is easy and about as safe as you can get. Hard-boil a few eggs. The number depends on how much silver you’re oxidizing, and how dark you want the silver to get. Place the hot & freshly boiled eggs in a container (this can be a plastic food container, a plastic zipper bag, anything that seals) with the silver you want to oxidize. If you’re using a plastic bag, seal it most of the way, but leave a crack for hot air to escape. Smash up the eggs, shell and all, making sure to get the yolk nice and mashed to release the sulfur. Then seal the container completely.
The amount of time you leave the silver in depends on the color you’re aiming for. If you play around with timing, pulling the silver after only a minute, or 10, or 30, you can get great variation in color from yellow to black. Make sure to turn the silver, or rearrange it in the container at least once during the process. Silver that’s touching other silver, pressed against the container, or coated in egg-white may not get evenly oxidized. Wash off the silver and eat or toss the egg. To remove the oxidation, pickle the silver in citric acid (see posting below), and scrub. Huge plus: your studio won’t smell like the sulfuric cloud that hangs over a paper mill!

Refinery Research

By Page on May 29, 2007 at 12:09 am

Refinery Research:

Over the past year and a half we have researched refineries that use only recycled metals & fair trade metals- determined to find a local refinery we feel supports our principals.

Most refineries will say that they use mostly recycled metals—this is true, particularly with precious metals. Precious metals are just too valuable not to recycle. However, roughly only 40% of the metal is reclaimed. Typically, reclaimed metals are mixed with new metals, which are purchased from large metal companies. It’s often unclear where these metals are coming from.

• Once metal is melted down together—it’s more or less impossible to trace its origins. This is why we think it’s really crucial to establish federal standards for recycled and fair trade metals. Too much responsibility is placed on the consumer, and it is nearly impossible to learn about the material’s history.

• Last summer we toured the Hoover & Strong Refinery in Richmond, VA. Hoover & Strong offers jewelers recycled metals in various forms & utilizes refining techniques that are more environmentally efficient. Their website is also a good source of information.

• Another refinery we think is doing good work is Precious Metals West, located in Los Angeles. While Precious Metals West is a smaller company than Hoover & Strong and doesn’t have the resources to be as progressive in terms of equipment and their manufacturing capabilities, they are very flexible and open with their information. Precious Metals West will allow you to source your own metals (either recycled or purchased from a responsible mine), which they will then refine for you.

• We are really trying to encourage both of these companies to begin manufacturing recycled chain. If you want to help out—contact

Below is information taken from Hoover & Strong’s catalog about how to best sell back you scraps & the steps that are taken to refine your scraps into usable metal.

How to sell back your metal:

Six ways to separate your scrap:

1. Gold scrap-karat scrap, jewelry scrap, filings & benchsweepings
2. Silver scrap & filings
3. Platinum
4. Palladium
5. Gold filled scrap, watch brands & optical scrap (keep each item separated)
6. Floorsweeps, polishings, sink sludge , emery & filiters

How to Maximize Your Returns:

1. Anything used in precious metal manufacturing should be turned in for refining with sweeps in a container. This includes store buffs, brushes, emery paper, etc.
2. Include the weight of the scrap
3. Separate metals, not karats
4. Separating your scrap increases your bottom line by minimizing your refining charges.
5. Separate magnetic from non-magnetic material.
6. Track the scrap in your shop
7. Send your scrap to a reputable refiner

How to make sure your saving your metal scraps

Sink Trap
A sink trap can be purchased or made for very little cost. Purchase a 5-gallon or larger container that will fit under your sink.

Separate Metal
Separate the metals in the shop, silver from gold.

Floor Mats
Capture scrap in your floor mats—Use heavy-duty rough pile floor mats. Keep a small separate vacuum to collect only gold scrap, filings and floor sweeps in the shop.

Have two separate wastebaskets one for regular trash, one for trash that has small amounts of precious metals.

What happens to your scraps when you sell them to a refinery?


Clean scraps are mixed with a special flux and then melted. The flux makes the metal more fluid and homogenous. The melt is then poured into a mold, the metal settles to the bottom and the slag created by the flux remains on top taking some of the non-metallic impurities with it. After smelting, the bars are returned to the vault to be weighed and sampled. The bullion remains in the vault until you have been paid for your scrap.


After your bullion has been weighed, drill samples are taken from each end of the bullion. This sample is fire assayed in duplicate to determine the precious metal content of the refining shipment. The assay lab does a miniature refining process on multiple samples to determine the precious metal content. The bullion karat is actually determined by the percentage of fine gold remaining following the assay process. The results of the assays must agree. If they do not, the bar is remelted to ensure that it is homogenous and resampled and reassayed.

And then there are Sweeps

Sweeps require more involved processing than clean scrap. It would be impractical to melt down a sweep because of its large volume and low grade gold content. The sweep is first burned at a low heat to incinerate the combustible material. It is then milled into a fine powder and sifted. By producing a fine blended powder, the sweep is made homogenous. A representative sample is taken and assayed to determine the fine gold content.

Refining to fine gold

The metal is now ready to be refined into its precious metal component. Hoover and Strong has invested in a new refining process known as the “Miller” process. Bullions from smelting are melted into a furnace. Chlorine gas is then bubbled through the liquid metal, turning silver and base metals into solid chlorides. These float on top of the melt and are skimmed from the surface to undergo a secondary refine to reclaim any silver. Once the process is complete the remaining liquid metal is at leas 98% pure gold. This is cast into anodes and electrolytically refined by submerging into a gold-based solution. During this process, fine or 24kt gold is plated onto the cathode. Both platinum and palladium remain in the electrolyte solution where they are later recovered.

Citric Acid Pickle

By Anna on May 24, 2007 at 10:32 am

Citric Acid Pickle

We’ve used a citric acid pickle for about 9 months now with great results. Citric acid is a fairly common preservative used for canning foods (i.e. it’s edible). Citric acid is non-toxic, in fact it’s derived from citrus fruits, and it’s relatively cheap and easy to find. It works fine as an alternative to Sparex or other chemicals to remove flux (halide salts used to ease the flow of solder), oxides and firescale after soldering.

Citric acid is much less caustic and tends to last longer than other pickling agents. It can cause eye, skin, and respiratory irritation -so be careful, but we’ve never gotten any burns. The biggest drawbacks are that citric acid has to be heated (as opposed to Sparex, which just works better hot), and it takes at least twice the time to work. There is some debate over the ideal water/citric acid ratio, but we use about 10:1 water to citric acid with good results. Some jewelers say that distilled water works infinitely better than tap, but we haven’t had any issues. It may depend on the mineral make-up of your tap water. You can buy citric acid (the technical name is ‘anhydrous fine granular citric acid’) at wholesale prices from spice & herb or chemical companies, and sometimes at the grocery store with canning supplies.

To dispose of citric acid pickle: neutralize it first with baking soda, and check with local waste management authorities for regulations (down the drain? cat litter?).

This site has art materials disposal info:

Citric Acid material safety data sheet:

More comprehensive Citric Acid Pickle article:


By Anna on May 19, 2007 at 2:10 pm


We first considered plating so that we could use
vintage, non-precious metal for some elements of our
first collection. We could enhance the elements by
plating them in precious metals, but still use a great
deal less gold. But plating is a dirty process… Is
it better to use that much less virgin material when
we are incorporating a process that involves caustic

In electroplating an electric current is passed through a solution that contains dissolved metal ions and the metal object that will be plated. The metal object serves as the cathode in an electrochemical cell, attracting ions from the solution. Generally, metal objects are dipped into a series of baths that contain various reagents to achieve the desired surface characteristics. A plating sequence usually involves several steps of cleaning, rinsing, stripping, and plating. In electroless and immersion plating the process is similar, but the metal coating is deposited onto an object using a chemical, rather than an electrical, reaction (EPA 1995).

The most harmful by-products of plating are sludge and wastewater containing the chemicals used to ‘clean’ the metal to be plated. The aqueous solution used for plating baths becomes waste water containing cyanide and metal wastes. Fortunately, working with valuable materials encourages precious metal platers to recapture any metal that might escape.

As jewelers trying to learn the source the metal we use, we run into a familiar problem in plating. Companies do not to trace each source of metal. It all goes into a big batch
together. Again, the vast majority of precious metal
is recycled because it is far too valuable to waste.
The larger plating companies we spoke with told us
that about 90% of all gold on the market is recycled.
But again, they don’t track the source of the metal
they use, they buy it from chemical companies like Technic or Advance Chemical who buy it from …who knows.
Small-scale platers have an easier time handling their
waste water. They may have permits like a small
science lab, and pay for their municipality to handle
the water treatment for them.

In our research of plating companies, we talked to a
lot of environmental organizations to get a clearer
picture of precious metals plating and it’s negative
environmental impact. Compared to other types of plating, precious metals plating gets a pretty good rep with the waste
prevention agencies, largely because they keep close
tabs on such valuable materials.

No one we spoke with had any recommendations of plating companies with a better than average track record.
NEWMOA (NorthEast Waste Management Officials Association, was the most helpful. They suggested the
following questions to ask a plating company:
-Has the company implemented any pollution prevention steps?
-Is the company doing anything to learn about pollution prevention steps they might take (e.g. an environmental audit)?
-Can the company cut back on water use?
-Does the company employ counter-current rinsing (this is a technique that requires less water)?
-Has the company explored any alternatives to chlorinated solvent cleaning?

Other Plating Resources on the internet:
– The EPA enforcement tracking site, where you can find the enforcement history of a company & check if they have ever been non-compliant or penalized.

– The Pollution Prevention Resource Exchange has a Metal Finishing Topic Hub with lots of information, and a reference section with over 100 articles on metal finishing.

– The National Metal Finishing Resource Center is a national compliance assistance center partly funded by EPA to help metal finishers improve their compliance with environmental regulations.