Bronze Clay Comparisons and a Relative Guide to Plasticity

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Lately I have been getting so many inqueries about bronze clay that it inspired me to create some tables that address some of the questions that have come my way.  I will also include the link to my PDF files  in case someone wants to print the tables.  Understand that I am new to the world of blogging so I hope I am able to link/attach/upload correctly.  As usual the information presented here is my opinion based on my methods and experiments done in my style, my kiln, and in my way.

bronze comparison table, plasticity table

Table 1 includes my most recent experiments with bronze clays.  The pdfs will be updated as information is gained and/or changed.

Table 1: Bronze Clay Comparisons by Melody Cooper 5/11/13[1]

Type of clay Workability Color Overall critique

 
Hadar’s Bronze Quick fire Coils well, but does have a tendency to crack if you let it get too dry or overworked.  Carving bone dry pieces is less precise than carving pmc, but still yields a pretty good result. Yellow goldish tone with a tinge of rose or copper color.  Close in color to a high karat gold, like 18K I have used this clay on many occasions over the past few years and still love it.  All the firings have been successful using the schedule suggested by the manufacturer.
Hadar’s Brilliant Bronze Quick fire Same description for workability as the Bronze Quick fire clay above Slightly less rose or yellow than the Hadar Bronze Quick fire if you compare them in a good light. I love the strength of this clay, excellent for rings.  The firing schedule was difficult to get just right with several pieces getting blistered and overfired.
Goldie Bronze

(I mixed equal parts of Soft with Hard)

 I have just begun working with this clay and therefore my opinions are based on limited experience.  I find that this clay is easy to mold, cut, sand and carve.  But having less success with coil making . A bit lighter in color than the two clays described above.  Close in color to 14K gold. The finished color is lovely, and the weight is light, also nice.  Less easy to work with than the clays by Hadar.  Easier to break in the bone dry stage than the Hadar clays.  Careful when carving, it is easy to take away too much too quickly.  Shrinks only 5%!
Bronz clay by Metal Adventures The first non-silver clay I used some years ago.  I used it again lately, having discovered an old package in the refrigerator.  Good for molding, cutting, coiling, carving.  Overworks and cracks easily if handled during drying stage. Similar to the color of Hadar’s Bronze Quick Fire clay.  Yellow goldish tone.  I made a bracelet and when polished to a high shine everyone thought it was 14k gold. I still like this clay a lot, but I like Hadar’s  and the Goldie Bronze clays better for their ability to be mixed when you need them.  The Bronz clay is sold in moist form that needs to be conditioned by wedging before using.  I prefer mixing from the dry clay in order to assure freshness.
Prometheus Bronze Really such a sandy and coarse grained product that once I opened the bag of clay I immediately placed it back in the package and so it has sat in my refrigerator ever since. Do not know since I never fired it. Maybe I will try to create a small sculpture since it seems unsuitable for anything else.  In all fairness I should mention that they may have improved this product since I purchased it early in the days of bronze clay’s advent.

 

Table 2 is my opinion of how various metal clays compare to each other as far as their plasticity is concerned.  As many of you know, my background includes extensive usage of ceramic clays and I often use ceramic terminology when it aptly describes a stage or technique in metal clay.  Plasticity refers to the malleability, or the quality of clay that can be shaped into something without breaking or cracking.

Table 2:  Plasticity Comparisons for Metal Clays that I have tried by Melody Cooper StickStoneLeaf.com

Level of Plasticity based on a scale of 1-10 with 10 being the most plastic Type of Metal clay Comments about Plasticity
10 Original PMC at its best Nice and moist.  Easy to coil, mold, roll into sheets, cut.  Beautiful to carve at bone dry consistency.  Boo hoo, boo hoo!  Why did they discontinue this formula?!
9 PMC3 at its best When PMC3 is fresh it is rating a 9 in plasticity.  Rolling coils is possible.  Great for carving at bone dry.
8 PMC3 when getting overworked or a bit dry and PMC Plus PMC3 starts to dry quickly and when it begins to dry the plasticity of this product drops one big point on my table of plasticity.
7.5 Hadar’s quick fire Bronze, Brilliant Bronze, and Copper clays If you use these clays when freshly mixed from the dry it is possible to create coils, texture, roll, cut, and join with relative ease.
7 Bronz clay by Metal Adventures If used while fresh and cold this clay allows quick molding, cutting, and some coiling.  Does crack easily during dry time if not left alone.
6.5 Goldie Clay Good for molding, cutting and filing.  Not as good for coil making.
3 Promethius Bronze Not very good for fine detail work due to sandy/gritty nature of clay.  Cracks easily.

 

I hope that these tables will be of some help.  I still intend to continue my Bronze Clay Firings notes with part 3 featuring Hadar’s Quick Fire Brilliant Bronze, soon!  Until then, may all your firings be successful and your creations be inspired.

 

 

Bronze clay firings notes part 2 Goldie Bronze

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5 items on left are fast fire bronze , 2 hearts on right are goldie bronze.

5 items on left are fast fire bronze , 2 hearts on right are goldie bronze.

Goldie Bronze captured my attention a while back and I really was anxious to get a chance to give it a go.  Still groovin’ on with my current loved technique using circle cutters, and molds made from plant materials, I embarked upon my journey into Goldie Bronze.

Before Firing:  I loaded the bone dry pieces in my bisque crucible on a layer of coconut charcoal about ¾” thick.  The crucible was loaded into the kiln onto 3 stacks of kiln posts 1” in height.  You can see this configuration in the photo in my past blog “Bronze clay firing notes part 1”.

Phase One of the firing:  Set kiln to fire at full ramp to 662˚F and hold for 30 minutes.

In between Phase One and Phase Two:  Let kiln cool slowly, but since it has fired to only 662˚F it cools pretty quickly.  At about 500˚F I open the door to let cool faster.  Once it has cooled enough that you can comfortably and safely remove with kiln gloves, remove ash by blowing away with a straw.  Please see firing notes part 1 for recommendations on doing this sanely.  Cover bronze clay items with a layer of coconut charcoal about ¾” thick.

Phase Two of the Firing:  Because the recommendation mentions during Phase 2 that the crucible should be covered (although they also recommend using a stainless steel crucible) I used a kiln shelf to cover the crucible during Phase Two.  Set the crucible on the posts  inside the kiln and fire full ramp to 1508˚F and hold for 40 minutes.

After Firing:  Let cool slowly to room temperature.  Make sure to carefully (wear dust mask) pour the charcoal from the cool crucible through a wide open mesh screen into an open container.

The Results and My Initial Impressions on Goldie Bronze:  The test pieces I made came out perfectly sintered. The color is less golden yellow looking than the Hadar quick fire Bronze clay, which really is not that noticeable unless you compare the two clays side by side.  I like the color of both types of clay. This is such an easy and fast firing process.

My next post will deal with plasticity evaluations, and more reviews on Goldie Bronze.  Be back in a day or two, until then happy trails to you. And thanks for reading.

Bronze clay firing notes part 1 and Disclaimer

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Top left: my kiln Top right: bone dry bronze clay items loaded into clay crucible ready for phase 1 of firing cycle Low left: crucible loaded into kiln on posts Low right: finished and polished pieces

Top left: my kiln
Top right: bone dry bronze clay items loaded into clay crucible ready for phase 1 of firing cycle
Low left: crucible loaded into kiln on posts
Low right: finished and polished pieces

For the past year I have used Hadar’s Bronze clays and I have had mostly wonderful results after a bit of experimentation.  But before I dive in and give firing notes, observations, opinions and advice, I would like to deliver my disclaimer.  These are my notes, my observations from my standpoint, based on results in my kiln, also reliant upon the kind of crucible used, and derived from the needs of my students.  Your results may vary.  To the best of my ability I consider factors such as ventilation, health, and safety, as well as respect for my equipment, when adapting the methods that I use.  I am not a fan of the kiln in the bedroom (or other unventilated space) approach to asphyxiating your cats, dogs, and children.  Please consider all the variables when preparing to perform your own tests.

So I had in my November 2012 notes that I fired Hadar’s bronze to 1520˚F in the second phase.  But I looked at Hadar’s updated pdf and it says that for a muffle type kiln the phase 2 is 1510˚F.  hmmmmmm.  So with that in mind I fired a bit over 1510˚F for this first in a series of tests, I fired to 1513˚F as you will see in the firing notes below.

Before the firing

The pieces were completely bone dry.  In a bisqueware crucible* I put ¾” of coconut activated charcoal** and then laid my raw bronze clay pieces on top. (you can see an image of this in my introductory blog “Dust, Rust and Pine”)  Then I placed the crucible on top of three stacks of two ½ kiln posts.

Phase One of firing

Set the kiln to ramp full up to 1100˚F and hold for 2 hours.  Let cool to room temperature.  I don’t like to destroy my gentle kiln, so I don’t usually engage in thermal shocking it by opening up the door until it naturally cools to 500˚F.

In between Phase One and Phase Two

Once the crucible is cool enough to pick up with kiln gloves I use a straw to blow away the ash that has accumulated in the Phase One firing.  Obviously do this in a conscientious manner observing respiratory, fire zone, and safety issues.  Then cover the bronze pieces with a layer of coconut activated charcoal at least ¾” thick.

Phase Two of firing

Set the crucible back in the kiln on the posts described above.  Set kiln to fire at full ramp to 1513˚F and hold for 2 hours.  Just before bedtime is the best time to do this so that you wake up in the morning to hopefully a treasure trove of successfully fired beautiful pieces!

After Firing

Make sure to carefully (wear dust mask) pour the charcoal from the cool crucible through a wide open mesh screen into an open container. **  This firing was quite successful, all the pieces sintered.

Thanks

A zillion thanks to Hadar Jacobson for creating such a fabulous bronze clay.  And also for her generous and informative pdf and firing guides.  Thanks most of all to my students for creating the need to share this information.

Tomorrow’s Blog

Tests results from Goldie Bronze!!

Thanks for reading!  Light and Love.

*I am a potter and I make my own crucibles.  Let me know if you want one!  More in following blogs on crucibles.

**Let me know if you want me to create a list of resources for these items.

Dust, Rust, and Pine

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Plenty of things to do and the list continues to grow with not enough crossed out items.  This year I am on a year long sabbatical from teaching classes at Pierce Community College, my usual full time job.  I thought that by now I would have had oodles of finished projects to show for the 10 months of leave, however life intercedes, and as they say rust never sleeps or as we say here on the ranch, pine needles never cease.  That is the cost of living in an urban forest, which was my dream come true, so when I look at it that way I guess I can revel in the joy of pine needle drifts from our most recent wind storm.

I do digress, this post is the introduction to my blog, and realizing that I could cross off a list item (ie. posting an intro to my blog) got me wired into thinking about lists in general. Here is the real reason I choose to blog in the first place, to share notes with my students and whoever cares to read about experiments in ceramics, glass fusing, metal clays, lampworking, hard metal fabrication, gardening, and life.

This past weekend I have been working with bronze clay and keeping close notes as to the process in order to compare and contrast the color, firing requirements, workability, strength, and happiness of the various types of bronze clays.  In my next blog I will post the results and notes (and pictures!) from the first firing with Hadar’s fast fire bronze clay.  Tune in tomorrow and until we meet again, may light and love be the order of the day!  And thanks for reading!

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