Sterling Silver Metal Clay Tutorial - Making Slip & Syringe Clay

With the new sterling silver metal clay, there is a lot to experiment with, and to push its limits to find out what IS its limit. The first thing I wanted to do was make some slip and syringe clay. I am used to working with PMC3 and I like using these two clay forms. Yes, slip can be made easily by taking a wet brush and painting it on the lump clay, but I don’t want to spend my time making slip when I need it now.

This is what you’ll need to make your own container of slip.

Small container with a lid

6mm round ball of lump sterling silver clay

A very small amount of distilled water (start with ½ teaspoon)

A clay shaper, flat or round

Place the lump clay into the container pressing it flat inside the container.	Add a small amount of water.
Mix pressing the clay against the side of the container until it is diluted to a smooth consistency.	Allow it to sit overnight and it will become very smooth.

 

Next is making the syringe sterling silver clay.

You will need:

An empty syringe (used up some from PMC3)

Snake roller

Small amount of Sterling Silver Metal Clay

Using the snake roller, roll the clay into a tube shape so that it can fit into the syringe.	Place the clay into the open end of the syringe, pressing it down into the tube with the plunger.
Keep pressing until all air is out.	Place clean tip on syringe.

While I am working with the clay, I keep my syringe sitting in a small container with a sponge and water. This keeps the tip from drying. I also store my brush there too, keeping it moist.

Recap of My Sterling Silver Metal Clay Testing Part 1

I spent a year testing the PMC Sterling Silver metal clay and wanted to post the results on my own blog. So, here is the very first post.

Questions, questions, questions! It seems the more I ask questions and get answers, the more questions I have!
In the next six months I will be testing different aspects of the new PMC Sterling Silver metal clay. This is the first post. I want to explore various methods for firing this clay. There has been a lot of buzz about speeding up firing time, mostly because of classroom constraints. When it takes over 1 1/2 hour to fire the sterling silver clay, it makes it hard to have an afternoon class about this new clay.

Let's start with the recommended firing profile. When and where you have time, this is the way to go. According to Mitsubishi, the recommended firing schedule for PMC Sterling Silver is a two step process. Fire the dry clay in open air on a kiln shelf for 30 minutes at 1000˚F (538˚C) for at least 30 minutes, longer for thick pieces. The second step (after cooling the clay) is to transfer it to a stainless steel container, surround it with ½” of activated carbon (at least ¼” apart) and fire it again at 1500˚F (815C˚) for at least 30 minutes.

I fired some base-line test pieces using the recommended procedure. Phase-1 took 43 minutes. This includes the time for the kiln to heat up to temperature and the 30 minutes of soak time at 1000˚F (538˚C). Phase-2 lasted approximately 51 minutes (not including cool-down time). All my tests using the recommended firing procedure came out perfectly! I was able to dome a disc and bend a link without either of them breaking. With that said if you are working on a special piece and want to make sure it fires properly, use Mitsubishi’s recommended procedure.

With my testing, I wanted to find a quicker way of sintering the sterling silver clay. In my first set of tests, I used a 50g package of PMC Sterling Silver metal clay and created five identical oval pieces with their centers cut out (35mm x 20mm and 4 cards thick). I only changed the process for Phase-1 and tried a variety of methods, shown below. All pieces were fired together in Phase-2 using the recommended procedure. This is what I found.

Test 1- Light the clay on fire
In my personal blog, a reader commented that she used a torch for phase-1 (thanks PPennee), so I tried her technique. I lit the clay on fire with a torch and then pulled it way allowing the clay to burn. If it went out, I re-lit it until it no longer smoked when heated. It’s interesting; while holding the torch on the clay there is no smoke. Only after I remove the torch does the clay burn with a flame and smoke.


The Specs
Weight after complete firing (both phases): 1.6dwt
Measurements after complete firing: 30mm x 18mm
Phase-1 time: 1.5 minutes
Sintered: Yes – bent nearly in half.

Test 2- Hadar’s Method
Hadar Jacobson, who tests and makes base metal clays, designed a faster phase-1 for her clays. She uses a camping stove and a stainless steel bowl with activated carbon in it. She places the unfired dry clay on top of the activated carbon and then covers the bowl with a fiber kiln shelf that has a hole in its center. She fires it until there is no more smoke coming out of the bowl and then places it in the kiln for the second phase firing. In this instance, I used her phase-1 technique and then Mitsubishi’s phase-2 technique.

The Specs
Weight after complete firing (both phases): 1.65dwt
Measurements after complete firing: 29mm x 19mm
Phase-1 time: 10 minutes
Sintered: Yes – bent nearly in half.

Test 3 – Mitsubishi’s Procedure

The recommended procedure.






The Specs
Weight after complete firing (both phases): 1.70dwt
Measurements after complete firing: 29mm x 20mm
Phase-1 time: 40 minutes
Sintered: Yes – bent nearly in half.

Test 4 – Torch for 3 minutes
I heated the piece with a torch for 3 minutes. I heated it to a very dull red, like when annealing metal on a fire brick, allowed it to cool, and then completed the second phase.






The Specs
Weight after complete firing (both phases): 1.85dwt
Measurements after complete firing: 30mm x 19mm
Phase-1 time: 3 minutes
Sintered: Yes – bent part-way but broke sooner than the others.

More Questions
I had more questions after completing these tests. I made four discs 18 mm in diameter and 4 four cards thick.

1. Does the clay shrink any more with longer firing?
   I fired disc #2 per Mitsubishi's instructions for 30 minutes. I then fired disc#3 per Mitsubishi's instructions for 2 hours in phase-2.
   Answer: both discs were the same size. They both measured 15.5mm after firing.
2. Is the torch fired (in phase-1) clay less strong than the recommended firing technique?
   Answer: no.
   I re-did the test with disc #4 and successfully domed it. I did however anneal the disc after doming it a small amount and then proceeded to dome it more.
3. What happens if I only fire the clay on the kiln shelf at 1500˚F (815C˚) for 1 hour?
   Answer: It doesn’t sinter (see Photo#1). The outside layer is metal and polished up to a silver shine with a brass brush but it broke very easily. The inside is dark gray and the outside is silver. I did learn though that it can still be sintered by completing the two phase process.
   
   
   
   Photo #1 left piece is not sintered.
   
4. What happens if in phase-1 I fire the clay on the shelf for just 1 minute at 1000˚F (538˚C) and then complete the recommended phase-2 procedure?
   Answer: It doesn’t sinter.
5. What happens if in phase-1 I fire the clay on the shelf for 10 minutes at 1000˚F (538˚C) and then complete the recommended phase-2 procedure?
   Answer: It sinters fully and is strong enough to be domed.
6. What happens if I place a disc inside a screen under activated carbon and fire it at 1500˚F (815C˚) for 1 hour? Will the air inside the screen area be enough to allow it to sinter? (See Photo #2.)
   Answer: No, it doesn't sinter (see Photo #3 )
   
   
   
   Photo # 2
   Photo # 3
7. If I am attaching two fired pieces together using oil slip can I bypass phase-1? If so, at what point does it not sinter?
   Answer: It doesn’t sinter when fired at 1500˚F (815C˚) for 30 minutes. I fired three pieces separately and then used sterling silver oil slip putting them together. Additionally, I added syringe clay as a decoration and as reinforcement where the bail and the base connect. At first it looked like it sintered, the new clay shined up, but when I applied force it all fell apart. (see Photo # 4.) I then re-applied more oil slip and syringe clay, and fired it to the Mitsubishi’s recommended firing with phase-2 holding for 2 hours. It fired perfectly and doesn’t come apart with applied force. I will need to test this again with firing the piece for a longer time.



Photo #4






Conclusion
If you are working on a prize pieced, take the time and complete it using Mitsubishi’s recommended firing. If you are willing to cut some corners and time, then try some of the above tests. I wanted to make sure the tests were repeatable so I re-tested the pre-firing using the torch and made this pendant from test disc #4 and oval #3. It seems to be working. I can say that in a classroom situation, where time is short, I may use the quick firing using a torch for phase-1 as long as the work is not very large and complicated. I don’t want to risk harming someone else’s piece of art! I will also be sure that students know the recommended firing schedule and the benefits of sticking to it.

I will continue testing multiple firing to see if longer firing allows the two fired pieces to adhere together without using phase-1 firing.