Questions & Answers

Questions & Answers

Dear Aberose,

Q.
I'm very new to PMC and just got my kiln. I'm using PMC3 and was wondering what difference the 3 different firing temps and times are for? Any advice would be appreciated.

A.
PMC3 can be fired using a variety of schedules:

1. If you are firing glass or stones that cannot take a higher temperature you want to fire at 1110F for at least 45 minutes. I know the mfg instructions say 30 minutes, but the PMC Guild PMC Connection strongly recommends a longer firing time if using this temperature.

2. You can fire at 1290F for 10 minutes or longer. This will give you a good, reasonably strong product.

3. You can fire at 1650F for 10-120 minutes. The full 2 hour firing will give you the strongest result with the maximum shrinkage. I usually fire to 1650 unless there is a reason to go lower--could be the content of the pieces or how long I have to fire something before I need to be somewhere else.

4. You can fire at any temperature between 1110 and 1650 with a good result as long as you do it long enough. Any temp over 1290 can be held for just 10 minutes. Lower than that and you need to fire longer.

Longer/hotter firing gives a stronger result, but does have more shrinkage (up to the maximum of 15%). by Mary Ellin D'Agostino, PhD, 09/2007

For basic instrucitons, technical information and charts, check out:

http://www.pmcguild.com/gettingstarted/startindex.html

The downloadable bookelt, "Getting Started in PMC" is a great place to start.

Also, there is a wealth of information at

http://www.squidoo.com/search/results/precious%20metal%20clay.

Q.:
How do I tumble and clean shot in the tumble machine?

A.:
Directions for Tumble Polishing PMC
Place shot in tumbler barrel and barely cover with burnishing fluid. You can use either a commercial jeweler’s burnishing fluid or 1-2 drops of dish soap in water. Brush pieces with stainless steel brush and place in barrel with shot and fluid. Tumble pieces for 30-60 minutes, check, and tumble more if desired. Change burnishing fluid when dirty.

Pieces should be free of ash (if made with burnable core), and thoroughly rinsed (if antiqued) before tumbling. Contamination of burnishing solution will cause unsatisfactory results. Very dirty solution and shot can cause pieces to become dull and gray.

If work pieces containing gold are tumbled, be sure to rinse shot well before next use. Gold particles in the solution will plate onto silver.

Be sure to change the burnishing solution frequently. Dirty solution can cause pieces to become dull and gray.

Cleaning Barrel and Shot:
If stainless steel shot becomes dirty (your pieces just won’t shine up and actually get dirty during tumbling), you can clean it by using a Coke bath. Rinse shot in strainer and return to barrel. Barely cover shot with flat Coke (or other non-carbonated mild acidic solution). Tumble for 15-30 minutes. Rinse shot and barrel. Repeat if necessary. If jewelry is blackened, repeat coke bath one more time with the jewelry in the barrel.

Burnishing Solution: Burnishing solution concentrate sold by jewelers is a specially formulated mildly acidic soap solution ideal for burnishing silver and gold. A drop of dish soap and water can be substituted.

Q.
My question is whether the silver is able to be melted down if not satisfied with its outcome. Would the silver be pliable once melted down and reshaped? Will the firing process cause it to be too brittle if reused? Really just looking at the recylability of the silver not clay after firing.

A.
After firing, the silver cannot be turned back into clay. However, the silver can then be used as any silver and melted to making casting grain, sheet, or wire. It is fine .999 pure silver. Mary Ellin D'Agostino, PhD

Q.
hi all, I have been trying various methods for bezel setting non-firable stones...my most recent experiment, i set 3 fine silver bezel cups in wet clay pieces. when torch fired, one melted the bezel cup, tho not the rest of the piece, one broke off of the piece while i was pushing the bezel against the stone and one seems to be ok....i scratched the bottoms of the cups and used plenty of paste to glop them onto the piece, so i was surprised about the piece that broke off...anyone have any tricks for using bezel cups with PMC? lynn

A.
I would recommend attaching them to the clay using PMC3 paste (the factory kind) and firing at 1650 for 1 hour. This will give you a strong bond that won't break when closing the bezels. Also, be sure the cups are absolutely clean--no grease or dirt on them. As with any silver findings, paste, attach, and check the attachment before firing and add more paste if necessary. You may find that recessing them in the clay helps as well as this will also create a compression bond around the bezel cup. Mary Ellin D'Agostino, PhD

Q.
Help with a PMC+ ring broken after firing. I am fairly new to PMC and am learning mostly by my mistakes. I've made and fired a PMC+ ring and mistakenly fired it for 30 minutes at 1470 not realizing that it had to be fired at 1670 for 2 hours, (later found out). It has broken in two, possibly three pieces. It is a bypass ring fired flat, and when I tried to bend it over the mandrel to make the curve it broke into pieces. Can I fix it with paste and refire at the proper temperature and time? Which paste should I use? I know there is an oil paste (tried it before and it made a mess of the piece - must have done it wrong.) Any help you can offer will be so greatly appreciated. Joy

A.
This is a very difficult question to answer without seeing the piece. First, as you mentioned, most of us do learn from our mistakes. Second, I honestly don't think that this particular ring can be salvaged because the fired broken pieces are flat not round like your finger. You already tried forming the fired piece around the mandrel and it broke into three pieces. Personally, I would start all over again from scratch and consider this a good learning experience.

For your info, the strongest metal clay for rings is PMC3. The PMC3 should be rolled out (five cards thick for strength) and shaped two sizes larger than your actual ring size (to allow for shrinkage) plus add 1/4" more for the ring joints. Place the rolled out clay onto the ring mandrel before firing it, not after it has been fired.

But -- if you are determined to try and repair your ring -- try to place the broken parts together, two pieces at a time, onto your ring mandrel and refit it to your size as you work on repairs. You may have three flat pieces but this could result into an interesting design?

Use PMC3 clay (not paste), right from the package, and gently smooth it into the two broken areas with a smoothing tool or with your finger. Then, gently brush a very tiny bit of water around the edges of the clay. Hold the two pieces together and count: 1001, 1002, 1003. Continue adding the other two broken pieces together the same way until the ring is completely reformed.

Dry the ring and, if any cracks appear after the ring (still on the mandrel ) is dried; fill the cracks again with the PMC3 clay. Gently add a little water onto a brush and brush the edges of the clay and dry the ring with a hair dryer. After the ring is completely bone dry, remove the ring from the mandrel and repair the inside of the ring the same way - by smoothing in the cracks with PMC3 clay and lightly brushing the area with a little water.

You could also try syringing designs over the cracked areas on the outside of the ring (ring again on the mandrel) to make it stronger where the cracks were. Again, brush a little water over the edges of the syringe. Bone dry the ring. Be sure it's sanded the way you wish the finished ring to look. Fire it for the recommended two hours at 1650 degrees F. Don't remove the ring from the kiln until it cools. Good luck! Let us know how it turns out. Aberose.

P.S.
Hattie Sanderson offers a fabulous "Ring Forming" DVD that I would highly recommend. Suggestion: you might try to find a PMC class in your area, taught by a Senior or Certified PMC Guild Instructor; to learn various PMC techniques offered at PMC Guild and PMC Connection

Dear Aberose, I really do appreciate your advice and I will be able to work with it this weekend. I will surely email and let you know what happened. It is worth a try and it sounds like I can make it work following your instructions. If it all doesn't go back together as it was, that's OK. This will be as you've said, a very good learning experience and we'll see what it wants to become. Anyway, I'm looking forward to trying this out. I'll talk to you again in a day or so. Thank you so much for your time and your thoughts on this. Joy

Q:
Hi, Im just begining to learn about PMC. I love working with copper. Is PMC good for sticking to copper or other metals while firing or would I have to solder ( can I solder copper to PMC? Thanks. Bill

A:
You may combine PMC3 with other metals such as brass, copper, sterling and fine silver. Look at the photo provided and see a few creations I've made using copper with PMC3. I applied the copper to PMC before firing, using copper as a bail and also as decorations. The copper does turn black after firing but the black can be sanded off using a Dremel and other sanding methods. Try applying Renaissance Wax to the copper before placing it in the kiln to protect the copper from oxidation. Aberose

If you can solder copper to sterling or fine silver, you can also solder it to fired PMC3 but be sure not to melt the fine silver. Experiment first.

Q:
Can PMC3 Syringe and PMC3 Paste be used successfully with PMC+?

A:
Yes. All types of PMC can be combined. Just fire at the longer hotter schedule. So, if you combine PMC3 and PMC+, fire as if it was all PMC+. If you combine anything with Standard, fire for the full two hours at 1650. Mary Ellin D'Agostino

Q:
How much Glycerin do you put with water in a spray bottle? Is it 1:2, one part Glycerin to two parts distilled water.

A:
I don't usually put glycerine in my spray water. I put it in a small dropper bottle in the proportions you note above. Then I add to my clay when reconstituting, if it seems to need it. The glycerine will make the clay more plastic. Mary Ellin D'Agostino

Q:
I was interested in using old plastics in making jewelry pieces. I am not a jeweler so I basically want to know if this precious metal clay can be used with bakelite or other old plastics, bone or other softer natural compounds as the focal points instead of hard stones?

A:
Plastics, bone or other soft natural compounds should not be fired with PMC as they would melt in the kiln, torch or hot pot - which are our three PMC firing methods. You could add the above after firing and cooling the PMC, saving space for them before firing; taking into consideration that all three of our PMC products shrink. (See our "PMC info" link regarding shrinkage rates for PMC, PMC+ and PMC3.) There are various ways to add objects to items after they are fired. Aberose

Q:
Is PMC considered sterling?

A:
PMC is 99.9% Fine Silver or, if using PMC Gold Clay; 22 and 24 carats. Aberose

Q:
Do you incorporate finding to hang the jewelry before firing?

A:
Yes! Bails can be incorporated when you create your PMC art jewelry pieces. Various mixed media metals can also be added for very interesting effects. Aberose

Q:
Do you have to use a kiln or have I heard correctly that it can be melted and applied?

A:
We offer and have three firing methods: Our 360 Evenheat Sierra Kilns and our wonderful Hot Pot and Torch Kits. Instructions come with each. Aberose

Q:
What basic tools would I have to have to get started and can I use a home oven as a kiln?

A:
No, we do not recommend using a home oven as a kiln. We do offer kilns and other firing kits mentioned above and we also offer some inexpensive to expensive jewelry making Tool Kits, Tools and various Books, DVD's and Videos. PMC classes are also offered in various parts of the country and can be found at PMC Guild and PMC Connection. Aberose

Q:
I have been interested in PMC for a few years now but have not taken the plunge when it comes to purchasing supplies, tools, stuff like that. I was thinking of getting a starter kit or buying a few items. I talked to one instructor and she said she does not recommend the Hot Pot. Being a beginner and not wanting to make a lot of pieces, why not start with a hot pot??

A:
Let me say first that metal clay does not care what your heat source is. Heat it long enough and hot enough and you will have a good result. Heat it too hot and it will melt. If you heat it too little or too short, it will be brittle. There are many firing options available and all have their pros and cons mostly having to do with expense, convenience, and consistency of use.

The reason to purchase a Hot Pot is if you are a new user of metal clay, don't know if you will continue using it, are concerned about using a torch (often this means you are concerned about the open flame or of the possibility of melting your piece), and only firing the low fire metal clays. Hot pots are a good choice for people who match one or more of these criteria. The Hot Pot, WHEN USED CORRECTLY, gives a perfectly good firing--I do not recommend it for firing rings or other items that need to be very strong unless the maker has no other firing options. These items should be fired in a kiln for a longer/hotter firing schedule than is recommended by the manufacturers. Even when firing such items with a torch, it is highly recommended that they be fired for longer than one might fire a pendant. The choice to fire twice is often made with a torch and kiln as well as the Hot Pot and reflects more on the particular piece and the person making it than on the type of firing system used. Finally, part of the concern over the Hot Pot may be due to people using the wrong fuel for it. When purchasing replacement fuel, it is important to buy the right kind. Not all gel fuels are the same! Unfortunately this means that the safest choice is to buy the Hot Pot branded fuel as the heating characteristics of gel fuels is not listed on the various brands found in hardware or camping stores.

That said, the torch is more versatile and I prefer it for that reason, but many people are concerned about using an open flame. A person using a torch to fire metal clay should be very clear on what is meant by "glowing orange" as many people have under-fired their pieces when their "glowing orange" is different than what experienced metalsmiths and torch fire-ers understand the term to mean. This is one of the biggest drawbacks to learning from books and instructional media. Nothing beats learning from a good experienced teacher in person.

As for stove tops, these can be a good option if you actually have a gas stove. These are not as common as many people think. While gas is cheaper to run, it is a lot less expensive to install an electric stove and that is what many builders have chosen in the USA. In my experience, you can't really just set it and forget it because you may need to adjust the flame while firing. Also, you need to be sure to use a stainless steel wire grid and not standard hardware cloth, which is usually galvanized and will deteriorate during firing. Camp stoves are far more problematic than the household range as the flame does not remain consistent--it changes as the level of fuel in the propane or butane cannister goes down and as the cannister becomes colder while firing. Hence the Speed Fire Cone, which concentrates the heat AND comes with a pyrometer so you know what your temperature is. The SF cone needs to be monitored as well. Also, the most consistent result will be gained if using a large BBQ type tank for the butane/propane--an adaptor is needed in this case for the SF Cone.

Lots of people like the Ultralite because of its small size and relatively low cost. It is comparable to the SF cone at its base price, but the special metal clay inserts may make it a little more costly. It does take longer to heat than the SF Cone, but does run on electric.

Kilns, obviously give the most consistent firing assuming one has a reliable pyrometer in the kiln. These are available in a wide range of options, but if one can afford it, a kiln with (or that can be retrofitted with) a digital pyrometer is the way to go. The kilns designed for use with metal clay products--Evenheat (sierra) and Paragon--are the best for using with MC because they are designed to have a very consistent temperature throughout the firing chamber. Mary Ellin D'Agostino