Make Your Pottery Shine Without Glaze: Sumi Von Dassow Explains the Basics of Burnishing Pottery

Historically, burnishing was a method used by early potters to make their pottery more watertight and sanitary. Nowadays, most potters turn to glaze for that purpose. But many choose to finish their work by burnishing because of the subtle, earthy beauty a burnished pottery surface possesses. A burnished pot also has a soft, tactile quality all its own. It is hard to resist picking up and handling a piece of burnished pottery.

In today's post, an excerpt from the bookLow Firing and Burnishing, Sumi Von Dassow explains the basics of burnishing pottery, from the tools to use, to a couple of basic techniques. - Jennifer Harnetty, editor

 


 

Potters who burnish are often asked, "what glaze is that?" by curious admirers of their work. Non-potters naturally assume that all pottery is glazed, and the glossy surface of a burnished pot seems like a different and intriguing sort of glaze. Though glazed pottery can be brighter and more colorful, a burnished pot has a glow from within and a warmth that glazed pottery doesn't possess. The difference which non-potters sense without knowing it - and which fascinates potters - is that the surface of a burnished pot doesn't wear a coat hiding the clay itself from view. Glaze is glossy and reflective, but the reflecting surface consists of a millimeter or so of glass covering the clay. Underneath this layer of glaze the rough stony clay is always perceptible, even if not always visible. A burnished pot can have a surface just as glossy and reflective as any glaze, but behind this glorious surface there is no hidden roughness. Even the feel of a burnished pot is seductive: while a glazed pot feels hard and cold, a burnished pot seems warm and almost soft to touch.  

burnishing_01-300x260There are two methods of burnishing a pot: rubbing the clay with a polished stone or other smooth object, and coating the pot with terra sigillata and rubbing it with a soft material such as a chamois leather. We'll discuss the former today.

Using a stone is more time consuming and takes a lot of practice, but can produce a higher degree of sheen. You also don't have to worry about the surface chipping or flaking off, and you can get a perfectly smooth surface with no brush-strokes or drip marks.

 

Burnishing Tools

Any very smooth object can potentially be used as a burnishing stone. Many potters use rubber or plastic ribs for burnishing, particularly on leatherhard pots. The back of a spoon is a popular tool, though it may leave greyish marks on the clay. One of the more unusual burnishing tools I've heard of is used by Wally Asselberghs: he uses burnt-out lightbulbs of various sizes on leatherhard clay, because they are easier to grip. He does switch to a stone to finish the job once the pots are almost dry.

 


 

Before you burnish, you have to make the pot!

Download your free copy of Three Great Handbuilding Techniques: How to Make Pottery Using the Pinch, Coil and Slab Methods for some great pottery project ideas today!

 


 

Burnishing Leatherhard or Black-hard Clay

Some potters find it easier to burnish a pot before it has dried completely. Timing can be tricky - you want the pot at the verge of dry, but with just enough moisture in the clay to allow your stone to glide across the clay without scratching it. Traditional leatherhard, the stage when a wheel-thrown pot can be easily trimmed, is a little too early. A leatherhard pot will show the marks of your burnishing tool as distinct little ridges, and in drying the rest of the way it will lose most of the shine you give it. Ideally, you want to catch the clay at black hard - when it is almost dry but has not yet changed color. If you burnish at this point, then cover the pot to slowly dry the rest of the way, perhaps even going over it once or twice more with the stone before it dries completely, you can achieve a good polish. One drawback to burnishing this way is that you won't be able to sand the pot before burnishing, so this technique works better with a wheel-thrown pot that can be smoothed with a rib when wet, or after trimming. If you want to burnish this way, you have to pay close attention to the pot as it dries, checking and rechecking it, and burnishing and re-burnishing it until it is too dry to burnish without scratching. In order to achieve the maximum level of burnish, Carol Molly Prier burnishes her pots four times, starting by first burnishing at leatherhard, immediately after trimming. If it is a handbuilt pot she scrapes it smooth at the leatherhard stage before burnishing. At this leatherhard stage she sometimes uses a flexible metal rib to burnish, instead of her stone. She burnishes twice more as the pot continues drying, before it becomes bone dry. Once the pot is bone dry she uses a soft facial tissue to apply a thin coat of salad oil over the entire surface of the pot. She lets it dry completely and then goes over the pot one last time with her stone.

 

Burnishing on the Wheel

If you are burnishing a wheel-thrown pot, you may want to use the wheel to make the burnishing process easier. David Greenbaum burnishes wheel-thrown white earthenware pots on the wheel in a two-step process. The first burnish is when the pot is leatherhard, using a teflon plastic rib. When the pot is bone dry he rubs it all over with olive oil and allows it to soak into the clay. He then uses polished stones to burnish the pot again on the rotating wheel. Usually he makes three passes to eliminate any ridges the stone might have left the first and second time. With the pot still on the wheel he goes over the surface one last time with the Teflon rib to bring the surface to a glass-like gloss. He uses a Giffin Grip to hold the pot on the wheel for burnishing - the small rubber 'hands' that hold the pot don't mar the surface as wads of clay might.

 


 

This post was excerpted from Low Firing and Burnishing, available in the Ceramic Arts Daily Shop!

 


To learn more about Sumi von Dassow, please visit http://www.herwheel.com/.


**First published in October 2009
Comments
  • another option, instead of covering with an oily towlette, is to fold a paper towel in fourths. You can then add a little oil to the towel and slide your stone across the paper in order to pick up a little oil. If you get too much you can either spread it around your pot, in the areas you will burnish; or wipe some off on the towel. This way you have more control over exactly how much and where you want the oil to go. It takes a little more time, but we have the best job in the world. Besides, anything that takes time to complete usually produces stunning results.
    Anthony

  • …just found out it’s David Greenbaum’s piece…nevermind..love fb..

  • just burnished a piece last week…now know why it wasn’t as glossy as I hoped…more times and too early

  • I like wrapping a bit of plastic bag around my finger and using the flat of my fingernail to burnish – I can really feel what is going on.

  • there is a trick that some potters use, clear paste wax (sometimes boot, or floor) applied and buffed to a satin shine after the firing also..i like to use “Mop and Glow” on my burnished post fired raku to seal in colors and protect the carbon black from fading..

  • a question please… I once tried to burnish a pot, got a nice sheen which disappeared in firing. Can anyone tell me what the firing protocol is for burnished stoneware (grog free)?

  • PS in an electric kiln.. firing techniques?

  • I have the same question as Tracey, and also I’d like to know abou the techniques used in the 2nd pot shown, white with black and gray lines. I think the pot has been slightly squared, too. Was that done befor burnishing??

  • I have found burnishing to be a uniquely low-fire process. At stoneware temps the clay seems to shrink around the sand or grog, and so loses the smoothness, thats my experience anyway. I finish off my burnished and pit-fired pieces with plain old wax, like candle wax, melted in a double-boiler while the clay piece warms up in the oven below. If you don’t warm the piece it won’t absorb the wax. I hold the pot with a towel, pour wax in and dump it out again, then brush wax on the outside. Finally, I polish the piece with a soft cloth. This process gives a very warm glow to pots, and waterproofs them to boot! Am

  • To answer Tracy, If you fire a burnished piece of pottery above about

    1832F it will lose its shine, however it will still be very smooth

    and you can restore the shine with a clear paste wax.

    Casey

  • i have found that burnishing works best on lower fired pieces.
    anything over raku temps will loose the look. but remain smooth.
    often, after treatments are used to keep the shine, from waxing to buffing.
    the technique best used for you will be the one that works best for you.
    i have found that when you use engobes on the surface i burnish once, slip trail, then burnish twice more. the last time i usually burnish with olive oil like i described in my first post.
    anthony

  • I find that c-012 to 010 is about right temps… c08 max.

  • I have the same question as Ginny, Oct 8th that was not answered.
    The pot with the black lines and teal top….. How is this look achieved. I am thinking it is slip trailed but can one burnish after slip trailing and not blurr all the lines.
    Please explain how this look isaacheived.
    Pat

  • yes you can burnish slip-trailed lines. when you burnish you have to go in the direction of the line so as not to distort it. once the lines are burnished into the surface you can go in any direction, just make sure your lines are knocked down. this is where the oil comes in handy for a piece past leather hard. make sure your lines are dry enough to burnish, and like i said, in the direction of your lines at first.
    anthony

  • The black pot you are refering to, looks like ‘naked raku’ There is info about it out there, fun to do. Look up David Roberts.

  • Can you burnish a pot and then put it in a Raku firing? I wonder if anyone can tell the difference in results between Raku firing a burnished and non-burnished pot. Does it affect the end result as far as glaze colour is concerned
    thanks!

  • How about burnishing a handle? Can it be done after it is pulled on a mug, for example? Could it be pulled in such a way that it is burnished as one pulls it?

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