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Ferric Firing - A Little Overfired But Still Nice

The other day the weather was perfect for a raku firing, it was sunny after several days of rain and warm.  I had some pots ready for ferric.  It seemed like all the planets were in alignment for a good firing but maybe they were just the tiniest bit off.  I'm still learning how to best adjust this kiln for this type of firing.  A few years ago I tested the pyrometer on this kiln against Wally Asselberghs' and we did see some discrepancy.  Not a big deal, you should never completely trust those things anyway.

I brought the kiln up to 500 degrees pretty slowly, maybe too slowly, it seemed to take forever.  Then I gave it some gas for a fast firing with the intent of getting to about 1325.  It didn't take too long before the aluminum foil saggar to start dulling, in a few places it had completely lost it's shine and was looking a little thin.  This is a signal that the pots are done but the pyrometer only showed about 1100 degrees fahrenheit.

I held the kiln at that temperature for 5 minutes in an effort to be safe then shut it down.  I waited another few minutes before opening the kiln but I was worried that the pots would be underfired since I was now seeing lots of area of shinny aluminum foil.  No worries, I could just restart the kiln right?  So I opened one of the pots only to find dark maroons, not the yellows and oranges I was expecting.  When firing with ferric chloride we usually see the color go from yellow to orange to red to maroon to white as the temperature raises.  These pieces have that full range of colors.  They are pretty but I think they need to be a little cooler.

Aluminum Foil Saggar, ferric chloride by Future Relics
Ferric Fired Pots

Next time I'll bring them up to 500 quicker, not soak for 5 minutes and get them out of the kiln faster.  I may also put too layers of aluminum foil on the pots to see if that gets me the colors I desire.  They did get lots of complements at Art-B-Que and I even sold a few of them.  So I'm not unhappy, I just want them to have more of the vibrant colors like I was getting at Penland in March with Linda and Charlie Riggs.

Check out the gallery page - Future Relics Gallery by Lori Buff


  1. That's wonderful, and no breakages too! (Us amateurs usually have something crack.) I think they're beautiful.

  2. They look great to me, isn't the ferric dangerous to breathe the fumes? I know the oranges you are talking about though and the ones I've been have been shiny. Do you use extra thick tin foil?

    1. The fumes are dangerous, I always wear a respirator.
      The shine comes from spraying a non-yellowing acrylic sealer or waxing the surface. These were still too hot to shine when I took the picture.
      I use heavy duty foil but have found that restaurant quality is even thicker.

  3. should the ones I have seen have been shiny orange and red

  4. I don't know a thing about ferric firing, aside from the fact that the pots are gorgeous. Glad to hear that some yours already sold. Even if the results aren't exactly what you were going for, someone else will love it.

    1. That's true Michèle, we potters so often get hung up on what we want the pots to look like that we don't always see how nice they really are.


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