Sunday, December 30, 2012

White Bronze Explorations

I've spent the last few weeks exploring White Bronze Metal Clay.  The clay comes in powder form and can be mixed easily.  The mixed clay is silky and flexible.  It was easy to work with and was quick to sand.   I was excited to see how the pieces came out once fired, but that's where my trouble began.  So far I have fired three different test pieces, each ending with different problems.  Below is a page from one of my firing notebooks, and at the bottom are the results.  Test Fire #1 was based on the directions from the clay, in the end the center appeared sintered, but the edges were fragile enough to snap off.   Base metal clays must be fired buried in carbon, this is done inside a vessel in the kiln.  For test firing #2 I altered my firing parameters based on suggestions from my vessel's manufacturer.  This time, the piece was far weaker and crumbled like a cookie when wiggled.  For my third test fire, I reached out to other metal clay artists working in bronze and adjusted my firing schedule accordingly.  This resulted in the piece splitting and then crumbling.  

I was reassured by other metal clay artists that initial explorations in bronze required several test fires since everything from the kiln type to carbon type to vessel type to bronze type effects firing, but was still a bit disheartened.  I contacted the manufacturer of the white bronze and they immediately responded.  You can see in my firing notes below their direct feedback on my trials.  The key points include the following:
-The water drop test used in other bronze clays to check for sintering, is not a valid test for White Bronze.
-Both phases of firing must be done in a kiln, buried in carbon - this includes the first phase where the binder is burned off.
-Even the small kiln I use for firing can have a 300 degree difference from the floor to the lid, so the vessel must be up on stilts to best achieve high temperatures.
-The lid should be off the vessel for both phases of the firing.
-When both phases of firing are done in the kiln, there is no need to cool in between.
-The following firing was recommended:
Vessel on Stilts/No Lid for entire firing
Piece buried for entire firing
Phase 1:  Full Ramp to 1000F hold 2hrs
No Cool
Phase 2:  Full Ramp to 1250F hold 2hrs
Test cooled pieces with 220grit sandpaper, if it is metallic it's good.

*** On a side note, the instruction manual for White Bronze is part of the manual for the entire collection of base metal clays and therefore a little confusing as they are all talked about together.  In the manual, it does say it is a brittle metal when made into thin pieces and recommends it being used in combination with other clays for strength.  The email response I receive basically asked why I would be using it alone to begin with and that it NEEDS to be used in combination with other metals.  That it should not be used alone and even if you do get it to fire correctly, customers need to understand that their piece will be VERY fragile.  This really is different than how it is presented in the manual.  I went back and checked on the manufacturer's website and no where does it note that White Bronze is any different than the other base metal clays, you only learn that once you download the manual which I imagine most people do not do until they order it.  This is something which I find a bit frustrating, it should be more clearly noted as part of the product description.  I really didn't see the red flags until the manufacturer questioned my use of it because the manual is not that direct.  My persistence in firing it correctly is partially to see the process through and partially to complete the handful of pieces I have in White Bronze that are waiting to be fired.

So my next step?  More test pieces next week based on the above suggestions.  Wish me luck!

Sunday, December 23, 2012

Alcohol Ink Patina on Metal Clay

As I got to the finishing stages of this series, I knew I wanted to really bring the texture out and that the best way to do that was with a patina.   Liver of Sulfur is a traditional way to get a variety of tones, but requires precise timing for colors beyond black and a strong stomach as it does stink up the immediate area.  In looking for another option, I began experimenting with alcohol ink on the recommendation of a friend and have really been happy with the results.  Alcohol inks are sold in the scrapbooking section of most craft stores.  They are a solvent based ink and work great on non-porous surfaces, from metal to glass to super glossy paper and they come in dozens of colors.  I wanted to antique this piece with turquoise tones to really draw on its references to the ocean.  I took my fired and polished pendant and just touched the tip of the ink bottle to the surface and let the ink run through the crevices of the texture.  It only takes a few moments to dry and then I start buffing it off with a super fine piece of steel wool.  I also like to dab a little on my maker's mark on the back to pronounce it a little more.  I clean up edges and brushes (if I use them) with rubbing alcohol.  Remember to protect anything you don't want to be stained by this ink, such as findings or stones.  Since I am using the ink as a patina that sits down inside the texture and all the ink has been removed from the surface, I do not seal it because it is no more likely to rub off than a liver of sulfur or other such patina.  

Sunday, December 16, 2012

Tumble & Shine

Once I resolved the bails on this small series of simple pendants, it was time to fire and tumble them.  When silver clay is fired it does not come out looking shiny and metallic.  When I first tried metal clay I thought I was under-firing it because it kept coming out white.  Now I know that white is simply the fire-scale on the surface of the metal (below left).  It easily comes off with a brass brush, but leaves the silver sort of matte and in need of polishing.  A tumbler is a great way to polish up your pieces (not just metal clay) and it serves to help work-harden your pieces.  It also softens burrs that might be on your metal.  Tumblers range in price, I use the small inexpensive one above and can fit a number of pieces into it.  It's a simple tool, fill the barrel halfway with stainless steel shot (bought with the tumbler), a small amount of cleaning solution (see what your instructions recommend), place your pieces and fill with water just above the shot.  I run the tumbler for 2-3 hours depending on the degree of tumbling the pieces appear to need.  Below you can see the difference from the white fire-scale to the shine out of the tumbler.  A word of caution, soft materials such as pearls and turquoise may react badly with your cleaning solution, so know its compatibility and be sure precious metals are actually precious or the stainless steel shot may reveal more than a high shine!


Sunday, December 9, 2012

Hidden Bails in Metal Clay

For the largest pieces in this series, I decided I did not want the bail to become a decorative element.  It was important for these pieces to maintain their simplicity and that meant building hidden bails for them.  I rolled out my clay and decided an elongated oval would be the best shape and cut it to the length of the entire back.  I chose to wrap it around a straw and made sure it had been rubbed with olive oil to prevent the clay from sticking.  After cutting the oval, I slid my pin tool under one end and gently lifted the piece off my working mat.  I draped it over the straw and gave it a moment to set up.  I wet the back of my piece and placed pasted where the two ends of the bail would come into contact with the pendant.  I lifted the straw and placed the bail, gently pressing each end to secure it and cleaned up around its edges.  Once the piece began to dry enough so it would hold its form, I gently twisted the straw as I pulled it out.  I didn't want to wait until it was completely dry because I was concerned it would shrink too tight around the straw.