Obvara
Obvara pottery, sometimes referred to as "Baltic Raku" is a simple and primitive ceramic technique that is akin to traditional raku firing and frequently used by pit fire, barrel kiln and saggar fire practitioners. But obvara firing is unique enough to hold a place of its own.
“Fermented ceramic is a 4-6 centuries old ceramics technology where the glass-like glaze enriched with metal oxides is replaced by rye-flour yeast. This peculiar, half-forgotten pottery tradition is not the cultural heritage of just a narrow Latgale region, but it is common to the three Baltic countries (Estonia, Latvia and Lithuania), Belarus, and Russia, the territory that is united by a tradition of rye cultivation and black bread. Every region has its own name used to designate this type of ceramics: 'rūdītā keramika' (hardened ceramics) or 'melnie podi' (black pots) in Latvian, 'raugo keramika' (sourdough pottery) in Lithuanian, 'обварная керамика' (in Russian scalded ceramics) 'poripott' in Estonian. The English version of the technique is 'hardened ceramic' or 'fermented ceramic'. It is a unique local tradition that is practically unknown outside the indicated region. Nevertheless, at the same time it possesses some similarity with the world-famous Japanese and American raku techniques, whose essence, from the American point of view, is manipulations with just fired and still glowing pottery after it has been taken out of a kiln." http://balticraku.eu/en/balticraku/
But before you go and Google "Baltic"...this is the area across from Sweden and South of Finland. Some of the old Russian "states" if you will. I you are really into history and interesting factoids (like finding out about the Singing Revolution and the Baltic Way) visit https://en.wikipedia.org/wiki/Baltic_statesen.wikipedia.org/wiki/Baltic_states
I have a personal bias about the use of the term “Baltic Raku.” I have to admit that. While the author in “Balticraku.er” suggests that there is a similarity, the author neglected to point out the differences between the two techniques. Where raku typically uses the chemistry of a glaze, obvara does not. There is no glaze involved in a traditional obvara piece. In the Western version of raku, Paul Soldner (and others) developed the used of the atmosphere around the glazed pot to alter the chemical form of the metallic oxides. Obvara does none of that. Obvara and Raku both use carbon as part of the process, but in Obvara the carbon is fully half of the technique and in Raku is typically a much smaller part of the overall effect. There are some pretty hefty exceptions to that Raku observation but each of those exceptions is more of a personal/stylistic/artistic expression and not the technique itself. As a general rule, Obvara needs oxygen to complete the patterning and Raku (in the West) denies the pot’s surface of oxygen (reduction).
My personal collection of material to work on obvara is all organic, mostly flour, sugar, salt and yeast. My collection of material to work on Raku is primarily inorganic (feldspars, silica and oxides) along with a material to cause the reduction in the container post firing.
So while both techniques do manipulate the pot after it is removed from the kiln, that is about the end of the similarity.
Essentially, the unglazed piece is taken from the kiln at something around 1400 degrees and dipped into a yeasty mixture, something like a thin waffle batter (we sometimes refer to it as "goo"). The goo is a simple mixture of water, flour (any bread grain will do in our experience), yeast and sugar. It's a very "bakerly" or "kitchenery" process...if you know anything about bread baking you will understand what is going on with the mixture. Some folks talk about the mixture "fermenting" but in reality, one is developing an environment where the yeast will enhance the development of the gluten strands from two of the proteins in the flour.
We use the typical and widely published recipe for our goo.
2 ½ pounds of all purpose flour
2 ½ gallons of water
1 packet of yeast (or a tablespoon if using it from bulk)
1 tablespoons of sugar
Why the rather strange measurements? I mean, who measures like that. The formula represents conversion to Imperial from metric. Could have stayed in metric as that is pretty much a standard for pottery folks.
Here’s the deal. I’ve run 100s of tests and fired 1000s of pots. When speaking with baking professionals, that yeast and sugar might (may) enhanced the development of gluten, but ONLY if the temperature is “perfect” for the yeast to do its thing. Even if conditions are perfect, the effect that the results from the yeast activity on the development of gluten is rather minor in the "big picture." We’ve done testing with the yeast, without yeast and without both the sugar and yeast and IF there were differences between with and without, we didn’t see them. We’ve also tested the “fermentation” time required and find that with the flour we use (all purpose from Costco), 3-4 days is too long from mix to use. We like to mix the goo in the morning of day one and use it the afternoon of day 2. Seriously! But it’s about the speed that the gluten will develop, and results from your brand of flour may vary from ours. The gluten begins to form the moment that water is combined with the flour. Test everything.
Now, some bubble popping. That foam on the top of the mixture that forms several hours (or sooner if the water is warm) is nothing more than CO2 and is the biological waste process from the yeast. It has absolutely nothing to do with the obvara patterns. Adding beer or champagne or sparkling water to the goo will not substitute for the yeast “stuff.” Drink the alcohol (responsibly) and your results will be more enjoyable than adding it to the goo.
To find out more about the role of gluten in the obvara process, be sure to read our “Part 2.” Ironically, Part 2 was written after Part 3. But, because of some overt plagiarism, there was a need to put the Part 2 into place sooner than later. The research that led up to Part 2 is in Part 3. You can read the two parts in any order.
Yes. We have tried various flours: enriched, wholewheat, bread, cake, semolina and so forth. We have added extra gluten flour to the dry mix. There is very little visible difference between these experiments in the finished work because of the type of flour.
We have tried natural dye stuffs and that was ineffective. Most likely the dye chemicals burned off, as most organic matter would. Even the flour is turned to black (or dark brown) carbon traces.
As the piece is removed from the goo, the gluten attaches to the pots and forms somewhat of a resist on the pots. As the pot is removed the gluten is bubbling and gooey. I often use the term “like snot” to describe the bubbling goo. Where the gluten attaches, the pot stays lighter (the "white" patterns in the examples). Where the gluten does not stick, the flour in the mixture is left to burn and carbonize the pot.
The longer the pot stays in the air after removal from the goo, the darker the carbon markings will be. It is possible to leave the pot in the air “too long,” letting the carbonizing flour and smoke overtake the light patterning, or make the edges of the patterns a bit blurred by the smoke. Yes, there is smoke (and rarely a puff of flame). Contrary to some writings, this is not a "smokeless" process. Not much smoke is involved, but carbon and smoke are buddy buddy.
There is sometimes some smoke that comes from the burning flour, which leaves a hazy quality to the piece. With some deft maneuvering that smoke becomes a decorative element to the pot. You can turn the pot to allow smoke to rise in some areas, leaving other area with cleaner edging. This is one of the few processes involving smoke that may benefit from a windier day as the smoke will not be able to blurr the pot.
When the piece has developed a look that we enjoy it is placed into water to stop the process (and the smoke blur). Dipping the piece into the goo at various speeds, double dipping and the direction of the dip has a lot to do with the color development as does the temperature of the pot. Edges, thin places in the walls and raised texturing will tend to cool faster and accept the goo differently than the body of the pot. Those cooler places, particularly heavy textures and edges will generally be lighter or white compared to the rest of the piece.
The pieces begin to cool immediately as the kiln is opened (duh). Hotter pots tend to be darker when dipped...hotter areas of a pot react the same way. Lips and ridges cool more quickly, so are usually lighter. If the pot is too cool (it's all relative :-) )...the carbonizing will not develop and again, the pot will be a rather bland tan(ish) hue.. There is about a 200 degree temperature window where all this action takes place. Timing is important as the pot is cooling rapidly through that heat window.
Generally speaking, the hotter the pot going into the mixture, the darker it will be. Nearly glossy black pots are from the hotter side of the firing range and tan pots are usually from the cooler side of the range. Really hot pots held in the mixture longer will yield fewer patterns. Cooler pots held in the mixture longer will possibly not carbonize as they cool below the threshold where carbonizing can take place.
Because cooling has such a profound effect on the color of the pots done in obvara and our pieces tend to be small, we work extremely fast and efficiently. A typical firing will encompass between 200 and 400 pieces...which brings up an interesting situation...
...it is possible (been there and done that too) to "cook" the goo by adding too many substantial pieces too quickly. The goo heats up and everything thickens fairly quickly. Part of this is because we're working with small batches of material...a typical goo batch is about 3 gallons. We have essentially cooked the batch of goo into a porridge...an unappetizing porridge. It’s a phenomenon akin to indigenous people using heated rocks added to a basket of porridge to cook their meal.
Because we do this process so often, we have developed a method of controlling the development of the goo. We set the mixture in a temperature-controlled room. This stuff smells awful...not having it sit around in the studio is a wonderful thing. I frequently refer to the "aroma" as bad beer going in and freshly baked bread coming out of the goo. Now that I think about it...a few corn chips and some bean dip and I'm doing mighty fine.
Of course, being LickinFlames that we are...nothing is completely traditional in our approach to obvara. Like our work with saggars and raku, anything will be tried, and everything is negotiable. We burn stuff onto, into, spray, and sprinkle as pieces are removed from the kiln. We continue to work on this technique with each firing.
Questions? You can always email Jim and ask him for some additional clarification.