Monday, April 30, 2012

PMC Sterling Silver Metal Clay Test - Soldering

by Janet Alexander
Technical Advisor



For this month’s PMC Sterling Silver clay testing, I focused on soldering. I explored the following questions over a series of tests:

1.   Does the porosity of the clay cause problems with soldering?
2.   Do I need to burnish the clay first before soldering?
3.   How well does hard, medium, and easy silver solder work with fired    clay?
4.   Does pre-melting solder to the piece change the metal’s malleability? 
5.   After soldering, can I form the metal without the sterling piece coming off or cracking?

I’d like to explain more about question 4, which relates to the changes of the metal. Melting solder onto the metal actually causes the solder to alloy with the metal (this is true with any non ferrous metal). The two metals combine at the molecular level to create a new metal with a different melting point. So, with this question I wanted to know whether the malleability of the new alloy differs from the PMC Sterling.

Test 1
In my first test, I made a two-tone ring with copper and metal clay. The center of the ring is made with fired PMC Sterling silver metal clay and the ring band is made from copper sheet.


 In my first experiment, I created a strip of textured clay 4 cards thick and fired it per the manufactures instructions. I only fired the clay for 30 minutes in the second stage firing at 1500˚F.


I then pre-melted hard silver solder to the back of the sterling silver piece.








Afterwards, I sweat soldered* the sterling silver piece to the copper.







Once I started bending the copper/sterling silver into a ring, the sterling silver started cracking.










Here are my initials answers to my questions:
  1. Does the porosity of the clay cause problems with soldering? No it does not.
  2. Do I need to burnish the clay first before soldering? No
  3. How well does hard, medium, and easy silver solder work with fired clay? Hard solder worked fine. 
  4. Does pre-melting solder to the piece change the metal’s malleability?  It might, I will perform another test. More on that below.
  5. After soldering, can I form the metal without the sterling piece coming off or cracking? In this test, the metal cracked. More below.

*Sweat soldering is the process of melting solder to the back of one piece and then attaching it to another piece by again melting the solder, thus connecting both pieces together.


With the questions of malleability and bending still unanswered, I devised two more tests.

 
Test 2
I created three PMC Sterling Silver metal clay bands using the same texture but made them 6 cards thick and fired them in the second stage for 2 hours at 1500˚F. I created three variations and bent them into rings with the following results:



  • Band 1- No soldering/plain PMC Sterling band bent into a ring without any problems. 
  • Band 2- I melted hard silver solder onto the band and then bent it into a ring without any problems. 
  • Band 3- I repeated my experiment from Test 1, but wanted to see if making the band thicker and firing it for a longer time would keep it from cracking. I annealed the metal after bending it a little and bent it into an oval ring with few problems. It was only on the final, sharp bend that I experienced any cracks - just two small cracks that I was able to solder with medium silver solder. I also soldered the join successfully using medium silver solder.



Test 3

I created a two-tone ring top using PMC Sterling and copper. I  domed it, and then soldered a ring band to it using easy silver solder. I used the plain PMC Sterling Silver ring band from Test 2 (Band 1).

The results: Everything soldered fine and the ring top domed without the sterling silver cracking.




My Conclusions
All silver solder types, hard, medium, and easy worked well on the metal with no burnishing required. I'm sure IT silver solder would work fine also.

Overall the sterling silver metal clay held up suitably while bending it into a ring band by itself. Doming and rounded bending of the fired metal clay also worked well. The sharp bending of the sterling attached to the copper was too much stress for it, but was easily fixed by making it thicker, firing it for a longer period of time in the carbon, and by annealing it during the bending process. Additionally, I soldered small cracks before they worsened. Sometimes even sterling silver textured wire can crack under these conditions. All in all, the fired sterling metal clay performed competently.

Join me at the end of May for my next report on PMC Sterling Silver metal clay. Until next time, have fun claying around!

5 comments:

kim said...

thank you for the great research Janet!

Janet Alexander said...

Thanks for tuning in Kim!

Lora Hart said...

Good tests Miss Janet. Did you sweat solder the sterling square to the copper (milled or clay?) before dapping? And maybe try a second test of the sweat soldered band to copper backing with thinner .925? 6 cards, even though it shrinks more, is pretty hefty for a two layer ring. Maybe the first cracks were an anomaly?

Thanks for doing the work so the rest of us don't have to :D

L ~

Janet Alexander said...

Hi Lora,
Yes, I sweat soldered the sterling square to the copper before dapping.
I didn't re-test the 4 cards PMC Sterling. Even with the thicker piece it still cracked (but cracked less) when I shaped it into an oval. I know when I have done this with sterling silver textured wire (non-metal clay), it tends to crack in places where it is thinner. For example the textured wire that is small beads, tend to crack or break between the beads.

ahnn said...

Great information you are relaying here. This helps a lot.

cash for silver