The other day while creating a custom order I thought I would include another idea for a bracelet. These were made only 4 cards think so I thought I would go with the thinner firing schedule of 750 degrees an hour to 1550. Unfortunately this schedule did not work for me and the inside of the object was powder.
Secondly and probably most important I had carved holes in the bracelet but due to its uneven shrinkage the holes elongated. Important note to self: For round holes, do the holes AFTER firing with a drill press.
Although Ive been very successful with small pieces and adding holes prior to firing.
Monday, November 3, 2008
Monday, September 29, 2008
Student Work
Heres a picture of student work from my recent Bronze Class on Sept 28, 2008. All the pieces were successful. We did put part of the pieces in Coconut Carbon and in Regular Carbon.
Saturday, September 13, 2008
Bronze Clay with PMC
I rolled out the bronze 6 cards thick. While the bronze was still very moist I pressed a piece of pre fired pmc into the bronze...I made sure there was a good connection between the two materials. After it dried using paste I attached a loop at the top with a prefired bronze ring. the loop had been laying around on my work bench for many weeks. But I wanted to use "old" clay to see if it fired properly.
I had no problems with the connection between the bronze and the pmc. The "old" clay fired fine and the prefired bronze worked nicely too. These are successful pieces.
So why can I fire pmc into the bronze but had issues with the "Metal Clay Finding"?
I had no problems with the connection between the bronze and the pmc. The "old" clay fired fine and the prefired bronze worked nicely too. These are successful pieces.
So why can I fire pmc into the bronze but had issues with the "Metal Clay Finding"?
Experimenting with Prefired PMC and "Metal Clay Findings"
I used a prefired piece of pmc with a "Metal Clay Finding" tube. I thought my best bet would be to attempt a clay rivet. So I drilled a hole into the pmc and wrapped the Bronze Clay up and over the Metal Clay Finding. And from each side of the pendant pressed the clay through the hole so that if it did not adhere to the pmc it would at least adhere to itself. That was a good call....Bronze does not adhere in sintering to the pmc and did adhere to itself....BUT the bronze ate through the Metal Clay finding. See the big hole? What the....??!! I thought FineSilver could be fired with Bronze Clay.....
Friday, September 12, 2008
My Beautiful Cactus Cuff is a Pile of Dust!
I posted this beautiful cuff bracelet on the Metal Clay Forum for the August Challenge. It got rave reviews. I couldn't take my eyes or hands off this beautiful piece. One day I was looking long and hard at the surface cracks of the cuff, wondering why they appeared. I noticed the piece didn't feel like"solid" metal. So I applied pressure and the core seemed spongy. The more I pushed the stranger this situation became....the surface broke and cracked further. Obviously the center is not a solid metal....what is it? As I opened the cracks the insides of the cuff began to pour out! The interior clay became a dust while the exterior sintered and formed a shell. What the...?!?
After entirely pulling it apart I was left with an outer shell and a pile of dust. I took photos and sent them to Bill. His response was basically that my kiln was not firing properly. Hmmmm, I've used this kiln for many projects including PMC, std PMC and lots of glass. I then made a second cuff and took it to another kiln. I anxiously waited for the long firing schedule to be completed....Only to end with the EXACT same results.
So I once again contacted Bill Struve. Now he was perplexed. How could both kilns not be firing properly? This is a head scratcher. Bill contacted me....heres is his reply:
>
> I think the problem comes from the thickness of the piece. The only
> pieces I've gotten to do that are those that were too thick for the
> schedule I fired them at.
>
> When the clay is heated too quickly for it's thickness, it will form a
> shell and the inside won't sinter. If it's heated up way too fast, it
> will puff up a bit and feel spongey as well. Her piece is so thick,
> I'm thinking that the rate of heat needs to be slowed to about 175F/hr
> or even less. This is exactly what I've been working on the last few
> days. In fact, I've got a preliminary calculation for it: 1 hour of
> heating per mm thickness. So, a 3mm piece needs to be heated over 3
> hours to the target temperature of 1490F, no hold time. You would
> measure the thickest part (width does not count, thickness makes the
> difference.
>
> If her bracelet was 8mm thick at it's thickest, then ramp at 186F/hr
> to 1490, no hold. (That would be an 8 hour firing). Find the thickest
> part, measure it, then ramp 1 hour per mm thickness to the target
> rate. No hold.
>
> On 1/4" x 1/2" x 3" pieces I ramped to 1490F over a 6 hour period
> (250F/hr), no hold. All pieces fully sintered with no signs of
> overheating and no carbon bumps.
>
> In the last 2 days I've fired 2 even thicker pieces (in 2 separate
> firings) that are 1-1/2" x 3/4" x 1/2". Same schedule, 250F/hr to
> 1490, no hold. They sintered fully but they are cracked just like they
> crack when heated too quickly by torch. I'm going to slow the heating
> down and see if this fixes it. This would then make sense and it's
> just a matter of taking into account the thickness of the pieces and
> adjusting the ramp speed accordingly. This is the kind of thing that I
> hope to see. This wacky business of mysterious non-sintered things has
> to have a logical explanation and this one seems simplest and most
> elegant...
>
> In the meantime, I have a piece that is 20mm thick, 26mm wide and 90
> mm long. According to my heating theory, this will take 20 hours to
> fully sinter and it should not crack. The piece weighs 5.6oz before
> firing. I'll let you know what happens.
>
> After that, I'm going back to thin pieces to see if I can cut the time
> some more and make it a no-hold firing. The only reason I have a hold
> time on the thin pieces is that I removed the hold when I was fixing
> the sintering problems on thick stuff. Now I think it can be done on
> thin pieces too.
>
>
> Mardel"
I have not yet had the opportunity to work further with this firing schedule but most definately will!
After entirely pulling it apart I was left with an outer shell and a pile of dust. I took photos and sent them to Bill. His response was basically that my kiln was not firing properly. Hmmmm, I've used this kiln for many projects including PMC, std PMC and lots of glass. I then made a second cuff and took it to another kiln. I anxiously waited for the long firing schedule to be completed....Only to end with the EXACT same results.
So I once again contacted Bill Struve. Now he was perplexed. How could both kilns not be firing properly? This is a head scratcher. Bill contacted me....heres is his reply:
"Hi Diane,
Mardel Rein of Cool Tools responded about the hollow bracelet problem:
> Hi Bill,>
> I think the problem comes from the thickness of the piece. The only
> pieces I've gotten to do that are those that were too thick for the
> schedule I fired them at.
>
> When the clay is heated too quickly for it's thickness, it will form a
> shell and the inside won't sinter. If it's heated up way too fast, it
> will puff up a bit and feel spongey as well. Her piece is so thick,
> I'm thinking that the rate of heat needs to be slowed to about 175F/hr
> or even less. This is exactly what I've been working on the last few
> days. In fact, I've got a preliminary calculation for it: 1 hour of
> heating per mm thickness. So, a 3mm piece needs to be heated over 3
> hours to the target temperature of 1490F, no hold time. You would
> measure the thickest part (width does not count, thickness makes the
> difference.
>
> If her bracelet was 8mm thick at it's thickest, then ramp at 186F/hr
> to 1490, no hold. (That would be an 8 hour firing). Find the thickest
> part, measure it, then ramp 1 hour per mm thickness to the target
> rate. No hold.
>
> On 1/4" x 1/2" x 3" pieces I ramped to 1490F over a 6 hour period
> (250F/hr), no hold. All pieces fully sintered with no signs of
> overheating and no carbon bumps.
>
> In the last 2 days I've fired 2 even thicker pieces (in 2 separate
> firings) that are 1-1/2" x 3/4" x 1/2". Same schedule, 250F/hr to
> 1490, no hold. They sintered fully but they are cracked just like they
> crack when heated too quickly by torch. I'm going to slow the heating
> down and see if this fixes it. This would then make sense and it's
> just a matter of taking into account the thickness of the pieces and
> adjusting the ramp speed accordingly. This is the kind of thing that I
> hope to see. This wacky business of mysterious non-sintered things has
> to have a logical explanation and this one seems simplest and most
> elegant...
>
> In the meantime, I have a piece that is 20mm thick, 26mm wide and 90
> mm long. According to my heating theory, this will take 20 hours to
> fully sinter and it should not crack. The piece weighs 5.6oz before
> firing. I'll let you know what happens.
>
> After that, I'm going back to thin pieces to see if I can cut the time
> some more and make it a no-hold firing. The only reason I have a hold
> time on the thin pieces is that I removed the hold when I was fixing
> the sintering problems on thick stuff. Now I think it can be done on
> thin pieces too.
>
>
> Mardel"
I have not yet had the opportunity to work further with this firing schedule but most definately will!
Monday, August 4, 2008
Saturday, August 2, 2008
Im Cracking Up!
I made this in 2 parts. THE LARGE LOOP: I used the product fresh out
of the package. Oiled up my hands (etc), added water to the product
and shaped immediately (no time to let it dry). Very little
manipulation time as well. I used very thick slip to help hold it in
place...On one side I poked the holes into the surface while wet (the
other side I used a dremel to make divets when dry.) I let this
naturally air dry (no heat, no dehydrator). AS it began to dry I
noticed cracks starting to form. I babied them with slip (a very thick
slip)...by the time it was dry there were no apparent cracks in the
surface. (see the before sintering picture).
THE SMALL LOOP: There was a little product left and it was drying out.
I added a drop of water and olive oil to it and mixed it well in the
palms of my well oiled hands. I just kind of laid out a coil, no slip
no forcing it to stay in place (no cracks before or after sintering
either) and went to bed. In the morning I was able to ever so gently
open the loop and force it around the big loop (without breaking, whew).
I sintered the loops at the SLOW recommended schedule ramping up at
25o degrees to 1550 and holding for 3 hours in the regular coal carbon
(the pieces were covered properly with the carbon).
I believe I did everything right. But it is obvious that when you make
bends with the product while wet and force it to stay in place with
slip it cracks....My next experiment will be the same project but I
will add either lavender oil or glycerin or olive oil to the product
to see if I can stop the cracking.
Shrinkage facts:
Original 35.36mm after 28.83 shrinkage 19% (widest outside measurement)
Original 18.28mm after 17.37 shrinkage 5% (inner circle)
original 6.99mm, after 5.65 mm shrinkage 20% (thickness of snake)
of the package. Oiled up my hands (etc), added water to the product
and shaped immediately (no time to let it dry). Very little
manipulation time as well. I used very thick slip to help hold it in
place...On one side I poked the holes into the surface while wet (the
other side I used a dremel to make divets when dry.) I let this
naturally air dry (no heat, no dehydrator). AS it began to dry I
noticed cracks starting to form. I babied them with slip (a very thick
slip)...by the time it was dry there were no apparent cracks in the
surface. (see the before sintering picture).
THE SMALL LOOP: There was a little product left and it was drying out.
I added a drop of water and olive oil to it and mixed it well in the
palms of my well oiled hands. I just kind of laid out a coil, no slip
no forcing it to stay in place (no cracks before or after sintering
either) and went to bed. In the morning I was able to ever so gently
open the loop and force it around the big loop (without breaking, whew).
I sintered the loops at the SLOW recommended schedule ramping up at
25o degrees to 1550 and holding for 3 hours in the regular coal carbon
(the pieces were covered properly with the carbon).
I believe I did everything right. But it is obvious that when you make
bends with the product while wet and force it to stay in place with
slip it cracks....My next experiment will be the same project but I
will add either lavender oil or glycerin or olive oil to the product
to see if I can stop the cracking.
Shrinkage facts:
Original 35.36mm after 28.83 shrinkage 19% (widest outside measurement)
Original 18.28mm after 17.37 shrinkage 5% (inner circle)
original 6.99mm, after 5.65 mm shrinkage 20% (thickness of snake)
Friday, August 1, 2008
Bill Struves Presentation July 2008, Firing Schedule
There are many different firing schedules floating around regarding the sintering of the new Bronze Clay. I am posting a photo of a slide from Bill Struves presentation of Bronze Clay at the 2008 PMC Guild Conference in Indiana.
what it says:
Current Recommendations
Firing Bronze Clay
Pieces 6 cards (2mm) thick or less;
Ramp the kiln at 750 degrees per hour to 1550 degrees F
Hold at 1550 degrees f for 2 hours
Pieces more than 6 cards (2mm) thick
Ramp the kiln at 250 degrees per hours to 1550 degrees f
Hold at 1550 degrees f for 3 hours
Mixture of thin and thick pieces should use the thick schedule
Hope this helps
Diane
glassjunkie.etsy.com
what it says:
Current Recommendations
Firing Bronze Clay
Pieces 6 cards (2mm) thick or less;
Ramp the kiln at 750 degrees per hour to 1550 degrees F
Hold at 1550 degrees f for 2 hours
Pieces more than 6 cards (2mm) thick
Ramp the kiln at 250 degrees per hours to 1550 degrees f
Hold at 1550 degrees f for 3 hours
Mixture of thin and thick pieces should use the thick schedule
Hope this helps
Diane
glassjunkie.etsy.com
Thursday, July 31, 2008
Bangle Bracelet
By rolling the clay I made little snake rings. I made a thick paste from the clay using water. The paste helped hold the snakes together as I coiled them. Without the paste the snakes had a mind of their own and straightened out into a curve while drying. I was using my dehydrator for drying and once I let them air dry I had less problem with this issue (but the paste is necessary)
Once the loops where dry I carved into them using my dremel. The drilling was fast and easy.
Once the pieces where sintered I used a brass brush and tumbled the rings. I then assembled them using sterling silver jump rings. To bring the colors together I used a liver of sulfur patina. I did notice a few of the skinny snake ends kind of sticking out but the easily bent in using pliers.
I did not do any measuring before or after. But will be more conscious of that with future projects.
Sept 12....Since my initial posting of this piece I soldered the jump rings. If you click on the picture it will take you to my etsy shop where I have a new picture of the finished piece. The soldering went well and did not efect the bronze clay rings. I tumbled over night for a bright shinney finish.
Once the loops where dry I carved into them using my dremel. The drilling was fast and easy.
Once the pieces where sintered I used a brass brush and tumbled the rings. I then assembled them using sterling silver jump rings. To bring the colors together I used a liver of sulfur patina. I did notice a few of the skinny snake ends kind of sticking out but the easily bent in using pliers.
I did not do any measuring before or after. But will be more conscious of that with future projects.
Sept 12....Since my initial posting of this piece I soldered the jump rings. If you click on the picture it will take you to my etsy shop where I have a new picture of the finished piece. The soldering went well and did not efect the bronze clay rings. I tumbled over night for a bright shinney finish.
My First Bronze Clay Piece
Made July 26 2008: Arizona Pendant This is the first piece I made using the New Bronze Clay . I made this piece from my own hand cut mold. This is the same mold I used for the charm swap at the 2008 PMC Conference in Indiana.
The material felt great in my hands and molded wonderfully accepting all the details of the mold. I did not take exact measurements, I did take before and after pictures on a grid. After sintering my estimate is 25% shrinkage.
Adding the bail to the back was a little bit of a challenge but after a couple attempts it worked out fine. It didn't want to adhere to the dried clay. I think I needed to use a thicker slip then what I had mixed.
The material felt great in my hands and molded wonderfully accepting all the details of the mold. I did not take exact measurements, I did take before and after pictures on a grid. After sintering my estimate is 25% shrinkage.
Adding the bail to the back was a little bit of a challenge but after a couple attempts it worked out fine. It didn't want to adhere to the dried clay. I think I needed to use a thicker slip then what I had mixed.
Bracelet Experiment
July 28 2008...If you click on this photo you will see the notations of the problems.
This is a copy of the email I sent to Bill Struve (inventor of Bronze Clay)
*Bracelet with issues:*
Ive attached a photo of a bracelet I worked on yesterday.Because of the heavier areas of this bracelet I ramped my kiln (Even Heat, side and top elements) at 250 to 1550 and held for 3 hours. I placed the metal container (with carbon under and over the bracelet) in the center of my round kiln.
You can see in the photo where it had a break before firing....The bracelet shape seemed a little "wonkey" so I gently tried to flex it into shape and it broke. I placed some slip between to breaks and wrapped clay around the area....but it came apart in firing. This area along with the areas that Ive marked "weak" did not fire properly. I can see that the material is crumbly (clay like). Although the one area I marked "good" appears to be very strong (will not bend).
My original seam came apart. This had been put together during the time it was molded. Knit together and as I worked it I applied clay and slip over the area to ensure it would hold together (along with a snake) and the seam still came apart.
As I rolled out and applied the 4 snakes around the base of the bracelet I had trouble with the product cracking. And as they dried they cracked even more. What seemed to work or help me accomplish this tasks was to work in a dab of olive oil to the product and then roll them out and twist around the base of the bracelet. The snakes fired nicely
I drilled holes and places head pins into the holes with slip (to set half drilled pearls onto later)...All the pins adhered very well..
If you can let me know what you think I can do to improve the issues Im having I sure would appreciate your help.
I will be working diligently over the next few weeks to broaden my experience and knowledge with the product. As I mentioned I have several classes lined up already for August and September. My students are very anxious to get their hands on this!
Bill Struves email reply........
This is a copy of the email I sent to Bill Struve (inventor of Bronze Clay)
*Bracelet with issues:*
Ive attached a photo of a bracelet I worked on yesterday.Because of the heavier areas of this bracelet I ramped my kiln (Even Heat, side and top elements) at 250 to 1550 and held for 3 hours. I placed the metal container (with carbon under and over the bracelet) in the center of my round kiln.
You can see in the photo where it had a break before firing....The bracelet shape seemed a little "wonkey" so I gently tried to flex it into shape and it broke. I placed some slip between to breaks and wrapped clay around the area....but it came apart in firing. This area along with the areas that Ive marked "weak" did not fire properly. I can see that the material is crumbly (clay like). Although the one area I marked "good" appears to be very strong (will not bend).
My original seam came apart. This had been put together during the time it was molded. Knit together and as I worked it I applied clay and slip over the area to ensure it would hold together (along with a snake) and the seam still came apart.
As I rolled out and applied the 4 snakes around the base of the bracelet I had trouble with the product cracking. And as they dried they cracked even more. What seemed to work or help me accomplish this tasks was to work in a dab of olive oil to the product and then roll them out and twist around the base of the bracelet. The snakes fired nicely
I drilled holes and places head pins into the holes with slip (to set half drilled pearls onto later)...All the pins adhered very well..
If you can let me know what you think I can do to improve the issues Im having I sure would appreciate your help.
I will be working diligently over the next few weeks to broaden my experience and knowledge with the product. As I mentioned I have several classes lined up already for August and September. My students are very anxious to get their hands on this!
Bill Struves email reply........
Thank you for the picture and feedback. Yes, joints are difficult. To make a joint, make up a slip that is thick, about the thickness of tooth paste or thicker. This takes a volume of water that is 40% or less than the amount of clay to be used for slip. Wet both surfaces of the joint by applying a little water with a brush. Add slip to one surface and press together for at least 15 seconds. After this, you can clean up the excess slip with a somewhat-wet brush.
The clay dries on exposure to air, so keep things covered with plastic wrap. You can also apply a small amount of water with a brush followed by a little olive oil, also applied with a small brush. When working with the clay with your hands, keep them coated with olive oil to prevent your hands from drying out the clay. Small cracks can usually be smoothed out with a brush that has a small amount of water on it.
The container with the carbon should be on kiln posts so the hot air can circulate around it. Some round kilns have heating from the top or sides - you should choose side coils if you have the option.
On drying, the material shrinks about 5%, so you will need to plan for that. For example, a ring dried on a mandrel will crack due to the shrinkage. This may be why the snakes developed cracks on drying. I would recommend that each snake be made just prior to adding it to the bracelet and wetting the surface with a brush just prior to and after adding it.
Overall, I think most of your problems can be eliminated by keeping the clay well covered and sparingly wetting the surface with water and olive oil. Also pay special attention to joints and do not restrict shrinkage when drying.
Thanks for asking,
Bill
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Bracelet with issues
