Aluminum Foil Saggars: An Easy Alternative to Traditional Clay Saggars

 

"Seaweed Vase," by Edgeworth Barnes was wheel-thrown, burnished with a stone, and fired in aluminum foil saggar.

Saggar firing was originally developed to protect wares from ash-slagging and flame-flashing in wood firings, but in contemporary use, with clean-burning gas firings, the process is used in exactly the opposite way: to contain fumes around a pot so that the pot to picks up color from the fumes. Saggars are the lidded containers used to contain and isolate pots during a saggar firing. Most often, saggars are made from coarse sculpture clays that can withstand repeated heating and cooling. But some potters make aluminum foil saggars that do the trick quite nicely.

Today, in an excerpt from her book Low Firing and Burnishing, Sumi Von Dassow explains how potter Edgeworth Barnes fires his pottery in aluminum foil saggars with great results. – Jennifer Harnetty, editor.

 


Edgeworth Barnes uses one part each of copper sulfate, fine sea salt, cottonseed meal, baking soda, and 1/2 part each copper carbonate and titanium dioxide in his saggars. For larger pots he mixes these materials with water to create an evil-looking bubbling liquid he calls “swamp juice” and brushes this juice directly onto the saggar to avoid having all the chemicals concentrated only near the bottom of the pot. He also uses coarse steel wool, copper wire and seaweed. For saggars for larger pots he suggests using two shallow bowls for the top and bottom of the saggar, and adjusting the height of the saggar by placing rings of thrown clay between the bowls. He punches holes in the rims of his saggars to allow airflow, and fires to 1600 degrees F (870 degrees C) in about an hour.

Saggar Firing with Aluminum Foil For a quick and easy variation on saggar firing, Barnes now prefers an aluminum foil “saggar.” He paints each pot with ferric chloride (sold as etching solution for printed circuit boards) using a cheap foam brush, rotating it on an inexpensive banding wheel with a plastic top as he brushes it on. Other potters spray this material using an inexpensive spray gun.

Edge Barnes’s kiln loaded with tin-foil saggars, ready to fire.

Inexpensive is emphasized, as ferric chloride is caustic and toxic. It will ruin good brushes, eat away at metal parts on a spray gun, and corrode your metal banding wheel if it comes into contact with it. If you choose to spray ferric chloride, you must wear gloves, goggles and a face mask and spray in a well-ventilated area. Despite all these serious disclaimers, ferric chloride is fairly commonly used because it reliably yields spectacular pink to orange colors.

After all the pots are coated with the ferric chloride, Barnes mixes up the same swamp juice in a shallow bowl with just enough water to make the mixture froth. Once this has bubbled up and increased in volume he touches the pot to the bubbling mass. This leaves a lacy deposit on the surface where it contacts the pot. The swamp juice can also be brushed or splashed onto the pot. The saggar is made with foil that has been crinkled up and then spread back out. He scatters a little coarse steel wool, raw cotton and wood chips on the foil. Next he places moistened seaweed over these materials. Copper wire or pieces of copper dish scrubber can also be added to the mix. Next the pot is placed, usually top down, onto all these items.

More seaweed, cotton, wood chips and steel wool are then placed over the pot. Finally, the foil is wrapped around to cover the pot and pressed into close contact. The operative words here are “a little” of each of these materials — too much combustible material can result in solid black pots if the foil doesn’t burn away.

The pots are tumble-stacked in a kiln and fired to 1260 degrees F (680 degrees C – about cone 017), at which point much of the foil will have vaporized. It is important to do this outside away from people and homes! Ferric chloride and the other materials will create very toxic smoke as they burn.


**First published in December 2009.

 

Comments
  • As I read the piece, it appears amazing the ways of the Potters, to drive out yet more amazing things. One day I may be able to do them on my own. Thanks for the article and kudos to Barnes.

  • Diann A.

    I have used this technique and it is awesome.

  • Sharon L.

    done in a gas or electric? I’m guessing gas since the fumes would play havoc with the elements… yes?…

  • Jennifer A.

    There will be dusty aluminum oxide left in the kiln from the burning of the aluminum foil, so a respirator should be worn when removing the pots and cleaning the kiln.

  • Marko F.

    Though I haven’t done this technique, I have lots of experience with Ferric Chloride, as I often etch metals in my mixed-media work. Wonderfully nasty stuff that will eat copper for lunch. Be careful and don’t have any ‘green-practices’ pretensions if you fire in this manner. Of course, the same could be said of foam-vaporization metal casting, one of my undergrad faves… A lot of what we do exacts an environmental price. Do it on a modest scale, do it outside and don’t plan to do s’mores while you fire.

  • I have also used this technique with great success. I usually fire the saggars in my raku kiln using various oxides including salt. My only problem is how to correctly dispose of the used foil, any ideas!

  • With regard to firing with ferric chloride, I am a little horrified by the idea. Chloride is very corrosive to metal kiln parts and any other iron exposed to the chloride and under humid conditions it continues to work more or less indefinitely. We know, of course, that iron and copper chlorides are somewhat volatile at firing temperatures which explains the visual effects. I would suggest, though, that the acetates of these metals would be much less corrosive and would leave no acidic residues. Whether the effects are acceptable is the question, and someone out there may already have the answer.

    Jack White

  • Madeleine M.

    going to put this on my “to do” list…

  • So, I only have an electric kiln. Is this something I could try? I’d assume that since the reduction is done by the materials in the saggar instead of by the fuel it should work, but will it destroy my elements? Would it be better if I eliminate the ferric chloride and stick to less corrosive things like wood, cotton, copper, etc. Also, are the fumes a problem? I do have a EnviroVent which should send all the nasty fumes outside.

  • Andrea T.

    WOW, ok then sounds amazing….not sure that I like the enviro unfriendly side to this, its even more unfriendly than the std things we potters do. But I’m curious, what if we don’t use Ferric Chloride and still use the foil etc. is there a reasonable result? Gas or wood for best results??
    Andrea

  • I cannot get this page to print–the paragraph, “Saggar Firing with Aluminum Foil”. Please tell me how I can get this.

  • Robert L.

    Yes, you can do this without the ferric chloride. I have done this with just copper wire, salt and baking soda, barrel fired and have gotten some pretty interesting results. Of course firing in a barrel makes the results a little more hit and miss as the heat is not always consistent. Good fun, though.

  • Thank you for the information. I have wanted and aimed to try this beautiful method, but believe I will pass on it now. Let us know, if a less corrosive/ toxic approach becomes evident!

    I too am a bit horrified… as though death of frogs in my yard, salmon fry downstream, neighbors-all- are something we needn’t calculate before opting to exact the uncounted price.

    I’ve no pretensions about the green-ness of my practice as a potter: I do know there is a source-stream prior to clay and materials reaching my studio, over which I do not exert control (except to be somewhat discerning about materials selection.) Once material is in my space, however, I do everything I can to see that no avoidable environmental toxic addition occurs. This means I save clay and glaze slop, dry it, and transport it on hazardous materials collection days in our rural area.

    Also, folks should know that aluminum poisoning is super common in animals. (See Dr. Gloria Dodd, DVM’s, online reports.) Pet hair samples reveal consistently super- high levels, as well as other heavy metal poisoning. Potters need to protect themselves from this material as carefully as any other we use.

    best regards, and thanks for this forum!
    Zola de Firmian

  • What is swamp juice…? (I am from Denmark, and I don’t know what this is…?

  • Hi. I understand that aluminium fumes are toxic

  • The pots are beautiful, but would you put your own health in jeopardy for a few orange pots? Ferric Chloride is so corrosive that it will burn out the inside of your nostral and lungs. It is very enviro irresponsible to use it, although the author has recommended all the precautions, but the fumes are released in the air and you are poisioning yourself, pets and your neighbors. Do not try it in electric kiln, it will eat up the elements.

  • The pot shown is beautiful, but the environmental cost to get it is just too high!

  • Carole S.

    Another saggar method is paper bag. Put the treated clay pot in a paper bag. Then tear strips of newspaper, dip them in clay slop/slip, wrapping around paper bagged piece. I usually wrap at least 3 to 5 layers of strips then let it dry for a while. Lots of fun and safe….but messy. I fired these pieces in a raku kiln.

  • Thank you for sharing this info. Very tempting to experiment it myself with less toxic material. Also, thank you Zola – well said.

  • Interesting article, but talk about not caring a dam about the environment!
    You can get good results without all those toxic materials. Experiment with other stuff please!

  • Thin slabs of clay work instead of the foil works well for a saggar also. Just break them off of the pieces after firing and the shards are interesting looking to boot.

  • clay sagars work just as well and introduce NO aluminum oxide into the kiln. is there an aesthetic reason to prefer aluminum foil? the residue can kill you. nearby flora and fauna won’t be happy either.

  • IF, after reading all the comments, you use aluminum with ferric cloride, make sure the liquid cloride doesn’t contact the aluminum. The chemical reaction generates a lot of heat as the aluminum is eaten away. Watch out for those fumes.

  • Linda from Denmark – After re-reading the artical, I believe “swamp juice” is the following chemicals – Edgeworth Barnes uses one part each of copper sulfate, fine sea salt, cottonseed meal, baking soda, and 1/2 part each copper carbonate and titanium dioxide in his saggars. For larger pots he mixes these materials with water to create an evil-looking bubbling liquid he calls “swamp juice” and brushes this juice directly onto the saggar to avoid having all the chemicals concentrated only near the bottom of the pot.

  • I use a loose stacked brick kiln, filled with sawdust, I wrap the pots in spanish moss, sissel string, seaweed, steel wool and copper scrubby’s and use only salt, iron oxide and copper carbinate in the kiln.
    Anything there that can hurt me? I live in a remote area so the fumes are not a problem to anyone around, but how about wildlife, would my fumes hurt them. Thanks to whoever answers for me.

  • Myra- just do a copy and paste (ctrl-c, ctrl-v). I too have not found a “print this artical” button.

  • I do a lot of Naked Raku firung. Want to try this method but the fumesfrighten me. I alresdy suffer frm a skin problem in my scalp which I do believe started with with the Naked Raku firings. Any suggestions to get similar results with less corrosive material. I am willing to sacrifice some looks.

  • I believe he’s using the Ferric Cloride and other chemicals, not only for the color it produces but also a chemical reaction that’s occuring on the pots as the Acids and Bases come into contact. It appears to me that this dendritic crystallization is the primary factor leading to the asthetic beauty of this method of pottery. Dendritic crystallization can be obtained with mild acids as well. I suggest anyone looking for a green alternative try something like this with mild acids, and the alkali metals and combustable materials in a traditional clay sagger. It would take some testing to perfect, but it could be well worth the effort.

  • DAWN A.

    Nice looking results, but I fail to see how an aluminum saggar saves time, effort, etc if you have all the clean up and toxicity issues. Clay saggars are easy to make, last for years of firing and by going to 1700 degrees (far too hot for aluminum) you can get all the same colors except Ferric Cloride yellow. Saggar colors can be created with completely safe ingredients, even kitchen and garden waste. Why poison your art space?

  • Roxanne H.

    Gee! Fear of the unknown sure brings some unfounded statements about environmental dangers and more! My hubby and I make lotsa these red pots with no hospital visits, no pet deaths! Wildlife in area is all fine too! Want to see results? Roxannehunnicutt.net. Really safety is important but fear is unnecessary. Just get educated on smart use of materials. We are adults, right? Some times these results are so desirous, one is so passionate that a few aluminum saggars in an electric kiln.though not too good for the kiln…well, I just did it a couple of times! The barrel works great for us! And I got a gas kiln so saggars are next !

  • Nancy W.

    HAS ANYONE WORKED WITH SIMPLE HOUSEHOLD CHEMICALS….BLEACH..AMMONIA…TURPENTINE..ACETONE…LIGHTER FLUID….WD40 ETC ETC ….LIKE PAINTING SHAPES ON YOUR GREENWARE …..ALSO WILL WAX WORK AS A RESIST FOR PAINTED SHAPES….THANKS FOR ALL THE GREAT INFO SHARED HERE

  • Maureen H.

    Thanks for the information but the toxic fumes would have me very worried.

  • Marcia S.

    There are lesser toxic elements like table salt, epsom salts. But the metal chlorides fume and provide stronger color. Just be careful. Mix just enough to use. Don’t be inhaling around the kiln.
    Marcia

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