Good News about Pearl Grey Steel, and Gradient Surfaces

This posting has two parts. Please be patient; it’s going to be long.

1. Firing Temperature of Pearl Grey Steel

No more high temperatures! It turns out that Pearl Grey Steel has the same sintering range as copper (1470°F/800°C – 1800°F/980°C). It can therefore be fired with copper and bronze in the same piece, at the low firing temperature of bronze.

How come I didn’t know this earlier? I guess I made the worst mistake one can make in research: making assumptions. I assumed that since the main ingredient in steel is iron, and iron’s melting point is so high, then the sintering temperature of Pearl Grey Steel must also be high.

How did I find out that this was not true? By mistake – which can sometimes be the best thing that happens in research. I accidentally included Pearl Grey Steel in a batch that was fired at the firing temperature of bronze, and I discovered that the Pearl Grey Steel sintered. I repeated this several times and it worked every time.

Here are some examples:


And here is Pearl Grey Steel with bronze only:


The firing schedule is the same as for my traditional Copper and Bronze Clay. It consists of 2 phases:

Phase I
Ramp at full speed to 1000°F/540°C (top loader); 1100°F/590°C (front loader)
Hold for 30 minutes to 1:00 hour, depending on the size of the pieces

Cool to room temperature. Remove ash and add more carbon if necessary.

Phase II
Ramp at full speed to 1470°F/800°C (top loader); 1520°F/830°C (Front loader)
Hold for 2:00 hours.

(I rounded off the numbers when translating them from Fahrenheit to Celsius.) Tip: once the first phase is over, take whatever box you use out of the kiln and place it outside in a shaded place, shielded from the rain.

By the way, I find this is the best firing schedule for bronze, copper, and Pearl Grey steel, whether fired by themselves or in combination with each other. With copper, too, it is unnecessary to go to high temperatures; I have had more success in sintering copper with this 2-phase schedule than with any other 1-phase schedule.

2. Gradient Surfaces

Although polymer clay is not my field of expertise, I have been studying a lot about polymer clay techniques to see if they can be adapted to metal clay. Some of them can, but with a few adjustments that are required mainly because metal clay is fired and not baked. The firing process can cause different (sometimes undesired) results when applying polymer clay techniques without these adjustments.

However, the technique for creating a gradient surface, known as Skinner Blend, can be applied in almost precisely the same way as with polymer clay. This technique produces a gradual transition from one color to another, and even to a third color.

Here are some examples. Starting from copper to bronze:

Copper to Bronze

This surface, once fired and finished, immediately brought to my mind the gradient paper I use for taking my photos. So, I just hung a tiny piece of jewelry on top of it.

"Cab" on gradient vbackgrounf - front view

Cab on gradient background - front view

Back view

Back view


This one is from steel to bronze:

Before firing

Before firing

After firing

After firing

And this one is from steel to copper to bronze:

Instructions on how to make the Skinner Blend can be found in almost any book about polymer clay.

Important note:: This technique will not work if one of the ingredients is silver or regular steel clay. I am about to start experimenting with White Bronze.

13 Responses to “Good News about Pearl Grey Steel, and Gradient Surfaces”

  • Otteline Says:

    This really is good news!
    All the pieces look fabulous.
    Hadar, do you ever find time to sleep?

  • Otteline Says:

    If I fire quick fire pearl grey alone, what firing schedule should I refure to? Is it the same as with mixed pieces?

  • heidi jo Says:

    oh my goodness! such magical results!!! i had better work on selling some jewelry to have some $ to buy more of your clays!!!! GORGEOUS!

  • Hadar Jacobson Says:


    Fire at the firing schedule that I have just posted on my blog. It’s good for both mixed and single-metal pieces.

  • Robin Hill Says:

    Hi, these are the quick fire clays aren’t they? Apols for the dumb question & kindest regards

  • Karyn R Says:

    Hadar – Can you explain the purpose of the 2-phase firing, and letting the box cool in between? Is there a reason we couldn’t just hold at 1000F and then go up to 1470? I’m assuming the hold at 1000 lets all the binders burn off, but that may be wrong. Thanks!

  • Hadar Jacobson Says:


    All are Quick-fire. For Pearl Grey Steel there is only Quick-fire.

  • Hadar Jacobson Says:


    I ask this question myself but I am not sure of the answer. Statistically, with this firing schedule I have almost 100% success with all types of clay. The one-phase schedule works, but about half the time I need to re-fire because of poor sintering. I have my theories as for the reason, but they are hardly scientific.

  • Sandee Butler Says:

    Thanks so much for trying the skinner blend on metal clay. When you were up here in Seattle for the workshop I was wondering if a skinner blend could be sucessful and it looks like you made it so. Beautiful pieces. Is there a certain order you would recommend ie.. copper next to bronze next to pearl grey or pearl grey in the middle?
    Thanks again for all the time you take to experiment and for sharing the results.-Sandee

  • Hadar Jacobson Says:

    Hi Sandee,

    You can put them in any order. Each of them will blend into the other. If you make something, send me a photo!

  • Christine Damm Says:

    Hadar, this use of the Skinner blend is very exciting– the results are amazing! I’m ordering my firebrick today to make the firing containers. I know I will be experimenting with the gradient colors. Thanks again for being a metal clay innovator!

  • Anita Leclercq Says:

    Hadar, you say you can get how to do skinner blend out of polymer clay book. do you have some instructions of how to do it with metal clay?

  • Hadar Jacobson Says:


    The instructions are the same.

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