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Testing a theory - Creating 'Raku Clay' earrings in an OLD enamel kiln (what I did, and the things I learned!)



Ceramics have always been somewhat of a mystery to me, I have enjoyed what little I have had to do with it since high school, and I've even taught a beginner hand-building class or two, but when it comes to a deep understanding of the world of ceramics, well, I have spent more time elbow deep in paint and resin.


So, with 2023 behind us, we are into a new year and looking to uncover new concepts, ideas and creations for our customers to enjoy! A few weeks ago I stumbled across a listing on Facebook marketplace for an old enamel kiln and got excited.


A deep dive on Google, Reddit and YouTube showed a huge list of possibilities for our customers (and me) to play with when it came to enamel and low-fire glazes. But it got me thinking, I wonder if you can fire earthen clay in a kiln that maxed out at 900 degrees (on a good day) with no ramp or controller.

So after some research, I figured I needed a low-fire clay that was happy with abrupt thermal changes.


Raku clay seemed a good choice given the nature of the process for which it is generally used.


Most Raku clays still needed 1000 degrees for bisque (which I knew I would not get) but after reassuring myself that the ancients fired as low as 600 degrees I figured I was making earrings anyway (and they were going to be thin and therefore likely dry evenly and retain little water) and we wouldn't be eating off them - why not?


It also seemed the best choice in terms of the limitations of the kiln (it was on or it was off). So I grabbed some Finneys Raku clay and hoped for some speckled pinky results that I could paint with gold after the fact.


All the gear and no idea


The process was easy enough, a lot like poly clay. I rolled it out using fabric to stop it from sticking, used cutters (eventually with glad wrap which was a lot easier), and smoothed the edges with wet fingertips, then I left the pieces to dry for 2 days.


As they were so small and so thin, I reckoned this was plenty of time, as I had made two hand-thrown bowls (for a later blog) which were much thicker, to allow me to compare dry times.


On the third day I was ready to fire them and after much research, I concluded that an appropriate approach would look like this:


  • Place the dried pieces on a bisque ceramic tile, and place it into the kiln cold

  • Turn it on and allow it to heat up to 900 degrees (this was to take 60 minutes)

  • Allow it to fire for another hour once the peak is reached

  • Allow the work to cool for 2 hours before opening the kiln


Whilst I knew I wasn't going to get full bisque pieces (and I would need to seal them to ensure body oils could not be absorbed by them once done due to the low heat) I hoped that 2 hours at 900 degrees would get us there with these wafer-like projects (hopefully sans explosions).


The night before firing, I prepped the cut-outs and matched them with the findings I planned to assemble them with. My low-fire glaze and enamels would not arrive in time for this set, so I thought I would hand-paint them after firing and seal the reverse with poly resin.


I laid them out on an unglazed ceramic tile and set them to the side for the morning firing (I had planned to prep a new Paint Your Pet painting in my studio anyway so figured I would fire them while I worked).


The view from Mordor (and all things firing)


The plan was to get to cone 010 - 011 (or somewhere in that vicinity) given how fast it was heating. I knew that around 300 degrees the impurities would be burned off, then at around 350 degrees the chemically bonded water would start being driven off too, and at 800 degrees the clay particles would start to fuse which is where we would ultimately get to. This clay chart helped me work it out, but given I wasn't ramping for 8-12 hours before and I was firing in an old kiln. it was not entirely predictable. I was this kiln's 3rd owner, as it had been sold to the lady I purchased it from, from a deceased estate.


In any case, it was time to fire the work! Below are the three stages it went through and the resulting bisque pieces. The first is before, the second is through the peephole, and the third is it cooling in the kiln.



Expectations VS Reality


What I had hoped for was slightly pinky/speckled ceramic earrings, that were firm, didn't crumble, soaked up the paint, and didn't return to clay when saturated with water. Ideally with no explosions along the way.


What I got was a little different. The first challenge was that the power tripped after it got to an hour and 15 minutes, with no explosions, but essentially this meant that my little earrings had 15 minutes at 900 degrees (if the kiln managed to get there). I made a call to let this be the end of the first firing and figured I would move to the 15 amp PowerPoint I have for the next one (after I got my electrician brother-in-law to have a look over the machine).


As I was watching the kiln, I was aware of the time it tripped, so I took the time marker and went ahead and left them in there to cool with the kiln door closed for another hour, then opened the kiln door and allowed it to cool all the way through. My kiln sits on a steel wheely cart so it was located just outside my garage door and very well-ventilated while the firing and cooling was in action (safety first!)


The result 'sounded' like ceramics when they bumped into each other, was a light white colour, and seemed pretty structurally sound. I didn't notice any crumbing or concerns aside at this point.



Paint, Seal, and Assemble


I was reasonably happy with the results given it was fired for all of 15 minutes at 900 degrees (rather than an hour) with a 60-minute ramp and a 60-minute cooling in kiln, before being moved into room temp. I also allowed it to cool to room temperature before moving on.


So it was time to turn it into wearable art! I liked the white and slightly pinky look to the clay so I decided to keep this project simple and incorporated two high-quality metallic paint pens (gold and chrome) to do the detail on these pieces. I then used UV resin to cover the rear of the pieces to provide a skin barrier - and then assembled the earrings as I had planned them. Here are some photos of that process.




A few things ...


I plan to do a second load using underglaze, glaze, and enamel coatings to see how they fare along with the actual firing time I had hoped for. I was surprised at how pink the pieces came up, which made me wonder if maybe the kiln was hotter than I was told it would be, and that the 60-minute warm-up contributed more to sintering than I thought. In any case, a second blog will be forthcoming to address those things but also the below:


  • How it goes from a hygiene perspective (is the poly coat enough to keep the body oils and makeup out (so that they don't smell over time / collect scent)

  • Will the partially sintered ceramic/clay be durable enough to last the distance?

  • How heavy will they be / what is the strength VS weight trade-off?

  • Will the acrylic paint pens be enough for longer-term wear

  • One set is destined to sit in water for a week, I am curious to know just how sintered we got to (to see if it will start to return to clay)

  • Will pieces explode in the next batch (did I get lucky)

  • Will enamels melt evenly stay on top of and not crack due to different expansion rates when I apply it to the next round of pieces

  • Will the low fire glaze and underglaze transfers work like they say they will (800 degrees)


Final Thoughts


So turns out it is possible, I mean primitive man made much thicker pieces with much less, so it had to be, just 'not possible' to today's standards. This may be one of the only blogs on the internet that thoroughly addresses this specific setup, so I hope that it is helpful to anyone who has wondered. Most forums said it couldn't be done and it seems this is because the full firing process is not followed, and so many ceramic traditionalists write it off as half done, and maybe it is (from a technical standpoint - I'll see if the studs now at the bottom of a cup of water fare over the next week). In any case, I know that the kiln was simply not hot enough to cause sintering and didn't result in a full bisque, but it may just have been hot enough to do what I needed it to do - at least as best I can tell before testing the wearability and durability over the next few weeks, we pulled it off.


If that changes I will be sure to come back and add an amendment to the blog linking to the next one where I elaborate on the testing phase ;-)


Below is the finished product as it is right now, and I have to say they look and feel great - very light to wear and it was a fun little project to do and to write about, and certainly worth a try if you are an enamel artist wanting to try something new or someone like me who likes a challenge and to see how far you can push something before it explodes ;-)


Jaana











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