Casting of silver causes a fire scale to form on the silver because of the high heat and exposure to air. When a silver piece is released fresh out of the investment material, it is very dark and scally. The first step is to wash and scrub off all the investment, then to drop the piece into the pickle bath.
I use an organic acid solution that it heated to slightly steaming temperature in a small crock pot. This is the pickle. The piece, depending on solution temperature, may stay there for about a half hour or so.
I usually am able to scrub off the blackness about half way through, then a bit more time in the pickle the silver will be the snow white as seen here.
This is actually the pure color of silver before it is polished. The slight pink seen on the metal is a blush of the copper that the acid draws out. Sterling is 7.5% copper to make it hard and more durable than pure silver.
After this stage, the sprue is cut off and filed smooth untill evidence of the sprue location no longer exists. Then comes all the polishing and burnishing to the final finish.
Some pieces have an applied chemical darkening to add contrast.
So after this point is where all the working with silver really begins. I love it!
Silver purchase prices have risen. It was in the ~$14/T oz. range and is now near the ~$18/T oz. area, for casting grains total cost delivered in my studio. Market price is always lower than purchase price. I just restocked with 10 ounces as this is the lowest cost break point weight for Sterling. But it also means I will have to adjust my finished goods pricing to follow the market. This is about a 20% increase in the price.
I have paid over $22.00 dollars per Troy ounce less than two years ago. The price varies constantly. For me it is what it is and the cost of my work will vary with my supply. I don’t fine tune it too closely with the market as that fluctuates every day. I use a fair estimate and definitely cover the cost of a new stock material purchase. 60¢ a gram is a good round actual cost estimate.
Small silver cost changes right now are not too critical when cost is lower. Silver is not presently the major expense against operating supplies and expenses and reasonable (but pitiful J ) labor earnings. A more expensive metal like gold is opposite. A few grams at $28/gram (14k) can radically change the cost of a project.
The total value of silver or any precious metal jewelry is not all in the cost of the metal, but it helps. Sometimes a lot.
These are two of the Celtic Three Dog pendants I recently cast in sterling silver. The background was darkened using Midas “Black Max” solution. A wax master for one of them is shown in the previous post. I made two pendants (using two wax master carvings) in a single pour in one flask.
I am confident now that I can make just about anything with lost wax casting. I have the process working very well and I have a good repeatable routine. I’m looking now for new designs and objects (subject matter) for casting.
I think I am going to get committed because of this lost wax mania. Mania is a mental illness marked by periods of great excitement, euphoria, delusions, and over activity. I have all the symptoms. Maybe it is a bad thing. To me it seems like a good thing and I really enjoy the “high”. Better than drugs I assume.
I often studied and thought of doing castings. Maybe because I was born and raised in a steel making town. Pour molten iron into a mold and out comes a new iron part. And it could be done over and over again.
I was first exposed to lost wax casting when I was a pre-teen and reading and studying all the model train magazines and information I could find. I was not so interested in running the trains but I sure loved reading and studying all the scratch building projects. Many of the small detailed metal parts were reported as being made by the lost wax casting process.
There must have been a lot of folks doing it as a cottage business to the model railroad market and maybe an offspring of the jewelry lost wax casting. The model parts were usually brass or white metal. I am sure it was done on spin casting centripetal machinery and perhaps something like plastic injection molding system.
I built some models from rather large white metal or zinc castings where I had to file off the flash, but I am not sure of the exact casting process.
On a small scale, how I am casting today could be used. But what I do is not anything near commercial production quantity. It’s quite an investment if all I wanted to do was a few model train parts.
I am in my comfort zone right now, just casting the pretty things I like to make. I really like working with the wax with both the CNC and manual carving. No subject or design is off limits, but it does have to fit within my tools and abilities.
Silver is my metal of choice right now, but I have experimented with brass casting. Just depends on what I am making. So much to try and do, it could drive me crazy…
I searched some Celtic illustrations looking for something I could CNC carve into a pendent for a necklace. This horse looking creature caught my eye. It looks part horse, part sea monster, and part Celtic with its typical Celtic knots look. Further research reveals it is a water horse, hippocamp or more friendly Scottish (Gaelic) or Celtic name, a Kelpie. So Kelpie it is... I thought I just had to put some work into the design.
My hands and eyes are not good enough to do this just with hand tools. I use Vectric Aspire to build the design digitally. The design took about two days of computer work and created around a quarter million lines of code.
The result is the wax carving shown in green wax that took 1:45 to run on my wax carving mill. That wax was used in lost wax casting to create the pendent shown in Sterling SIlver. That is a post-it note for the background and the Kelpie is under two inches wide.
I also made the wedding style band which was carved entirely by hand from a 3/16" (0.1875") thin, flat, square, wax blank . I always like to have several items when I am going to expend the energy to heat the kiln to 1350 degrees for several hours. Total kiln time is usually 10-12 hours per heat.