Going Low Tech: A Step by Step Guide to Burnishing Pottery

burnished pottery by Carol Molly Prier

Burnished vessel by Carol Molly Prier.

Burnishing is the technique of polishing clay to a beautiful sheen without the use of glaze. Ancient potters used these techniques to produce their wares before glazes and kilns were developed. Today, modern potters use burnishing to create works of great beauty.

Sumi von Dassow is one of those potters. She has been using low-tech pottery making techniques for more than thirty years. Though the burnishing technique is low tech, there are some secrets to really getting it right. In today's post, Sumi shares her step-by-step method for burnishing pots.- Jennifer Harnetty, editor.

 


An Introduction to Burnishing Pottery

by Sumi von Dassow

A suitable burnishing stone can be found at any lapidary shop, and often in museum gift shops or flea markets. Any kind of stone that has been tumbled in a rock polisher may be a perfect burnishing stone. An ideal stone is large enough to grasp easily, and has at least one perfectly smooth, slightly rounded surface. Any nick, bump, or sharp edge is likely to scratch the pot as it is being burnished: you can check a stone for nicks by running your fingernail over it.

For a first attempt at burnishing, start with a small rounded pot. Sharp angles, S-curves, flaring lips and grooves are difficult to burnish. To prepare the pot for burnishing, it should be sanded perfectly smooth when it is bone dry.

If the surface isn’t smooth enough, your stone will not be able to get into any little dips or depressions on the surface, and you will end up with dull, unburnished spots that the stone missed.

 


 
Once you've burnished your pot, throw it in the pit!
Check out Sumi's instructional DVD, Pit Firing and Burnishing, in the Ceramic Arts Daily Bookstore.

 


 

In addition to the pot and the stone, you need a towel or rag, a bowl of water and some vegetable oil. The first step is to wet the whole pot, inside and out, rubbing the water in quite thoroughly with your fingers. You need to rub the water into the clay before you start rubbing with the stone. This makes a bit of slip on the surface of the pot which helps to fill in any little scratches from the sandpaper, and dampens the pot so it doesn’t dry out too quickly while you are burnishing it. Then you re-wet small patches with a finger, starting at the rim, and rub with the stone until the clay becomes smooth and takes on a dull sheen. The towel or rag is needed to wipe extra water off your finger and to wipe the stone clean as necessary. It is important to start at the rim, burnish the whole rim, then burnish all the way around just below the rim, continuing this way in a slightly overlapping spiral pattern from the rim towards the foot. Once a burnished patch has dried, you will scratch it if you rub it again with the stone. For this reason, once you begin you cannot stop until you’ve finished. Working in a spiral pattern ensures that you are never working on a patch adjacent to a section that has completely dried: by the time you are working on the bottom, the top – which may have been burnished an hour ago – is completely dry again, but the bottom ring of the spiral is still damp and can still be safely rubbed with the stone. 

 

The second step is to cover the entire pot immediately with a light coating of vegetable oil and leave for 5–15 mins to soak in. After soaking in it leaves a whitish scum on the surface. Rubbed again with the stone, the clay takes on a high gloss. This step is much faster than the first, and it doesn’t matter what part of the pot is reburnished first. If there are patches of wet oil, you can work around them and reburnish the parts which are ready. During this step the pot will be easily marred by fingerprints and should be held with a hand inside. This will also help you avoid rubbing the oil off while you work. Lightly rubbing the pot with a chamois-leather after oiling and reburnishing will remove any extra oil and slightly improve the sheen.

The burnished pot can be decorated before firing by incising or by painting with terra sigillata or slip, or it can be immediately bisque-fired to cone 018. Though this is a very low temperature, it is high enough to harden the clay and drive off the internal water, without sacrificing the shine you worked so hard to achieve. Because of the very nature of clay, firing to a higher temperature dulls the burnish. Clay is made up of flat particles, called platelets. Burnishing works by pressing down the clay platelets on the surface of the pot, so they all face the same way and thus reflect light the same way. As clay is fired, it loses its platelet structure, so the higher the firing temperature, the more burnish you lose. With a suitable clay, cone 018 is hot enough to harden the clay without sacrificing too much sheen. Even if you are planning a subsequent firing such as a pit-firing, it is a good idea to bisque-fire your burnished pot to ensure that the finished pot is adequately durable, and to help the pot survive the fast temperature increase that is typical of many alternative firing methods.

Burnishing Pottery - Step-by-Step

 

  1. Wet the entire pot, inside and out, with your fingers dipped in water, then re-wet the inside of the rim. Work the water in well. With dry fingers, rub the stone on the dampened area, being sure to avoid leaving un-burnished streaks. If you have to rub hard to get the clay smooth, or if scratch-marks from sanding remain visible, you are not using enough water.
  2. Once the inside rim has been burnished all the way around the pot, wet the top of the lip and burnish. The lip tends to be the most difficult area and should be carefully smoothed and rounded by sanding. As you burnish, bits of clay will collect on the surface you’re working on. Use the back of your hand to wipe these bits off so that they don’t cause scratches. Wipe clay off the stone with the towel or your thumb.
  3. After burnishing all the way round just below the rim, continue in a spiral pattern towards the foot. When you dampen a new patch to burnish, slightly overlap the previously burnished area above. As long as an already- burnished spot has not changed colour (indicating it has dried completely) it is safe to go over it with the stone. As you progress down the body of the pot you can dampen fairly large areas and run the stone quickly over it horizontally and then more carefully vertically. Some people find it easier to burnish with a circular motion.
  4. The last spot to be burnished is just above the foot (which is not burnished). Note the colour difference between the just-burnished area near the foot and the dry area at the rim.
  5. The burnished surface is covered lightly with vegetable oil.
  6. Holding the pot with a hand inside to avoid touching the surface, the pot is re-burnished wherever the oil has dried to a whitish scum. Burnish around patches of wet oil until they dry. If necessary, extra oil can be wiped off with a finger. If the stone scratches the oiled surface, add more oil and wait for it to soak in.

 


 

For more interesting decorating techniques, download your free copy of Five Great Pottery Decorating Techniques: A How-to Guide for Decorating Ceramic Surfaces.

 


**First published in April 2011 
Comments
  • está bruñendo conuna pieza seca? yo bruño pero con la pieza en estado de cuero.

  • this is the exact method used by the potters of Mata Oritz, Mexico. utube has some excellant videos of some of the people there using this method, the best being one featuring Carlos Carillo. the story of Mata Ortiz is one every potter should know. it will humble and inspire you all. their finished products are now world famous, some selling for thousands of dollars.

  • I like to burnish certain areas of my pieces while the clay is still leather-hard. I make my own burnishing sticks by mounting a polished piece of Teflon rod in a wood or bamboo handle, secured with a wrapping of soft copper wire. The Teflon rod, usually 3/8″ diameter, is made into a pointed bullet shape, and polished to a sheen before it’s mounted. Black Delrin rod stock also works for this, but it’s harder than Teflon and not as easy to polish. But I agree that grog or sand are to be avoided. Any good plastics retailer should have these materials in stock.

  • i might add that the potters of Mata Ortiz do not have access to a ceramics store. they dig their own clay and minerals for colors and use stones for burnishing. their brushes are handmade from children’s hair, most attached to ink pens with the innards taken out. one of the utube videos shows a woman sitting at her kitchen table burnishing with a stone. the pots are low-fired outside using dung or wood. many of the potters now do demos at various places in the US and have a calendar of upcoming events.

  • liliana, usted lata brunir en el casa. no, hacer no arena en el casa o adonde su ventoso.

  • That is the beauty of ceramic work…no matter where it’s being done. We can always find ways to accomplish our tasks and manifest our creativity. Ceramics is at once the most sophisticated and the most basic of crafts.

  • Burnishing can also be done with the aid of the back of a spoon or a bone handle knife. I use both of these implements to burnish some of my pots. My all time favourite however, is a smmoth river stone and I usuall look for one that offers a good grip. Norma / April 25, at 3:45 pm.

  • The pot shown at the top of this article is beautiful and has a leaf patern decoration. How is it done, so that it doesn’t take away the shine? I use a lot of burnishing in some of my pieces, and I love the very act of burnishing…I can burnish any of my worries away!!!

  • A potter, part native American, demonstrated the burnishing techniques of his ancestors – using a Wal-Mart plastic shopping bag. Also, we did not let the pots dry completely, but burnished when there was a little dampness left. Using terra sig was a choice depending on the clay body.

  • I’ve been burnishing pots for a few years, and I never heard of using oil in it before firing. I was taught to add oil after the firing while the pot was still hot, and on blackware only…

    Three years ago I made a new technique for getting the same look as burnished wares, but it was 100% waterproof. For a stoneware clay body, you mix stoneware casting slip and clear gloss glaze (^06 type) in equal quantities. You apply it to the surface of a leather hard pot and wait for the coating to reach leather hard. When it is, you burnish with a river rock or a glass marble. It looks the same as regular burnished wares, but it holds water and my experience is that it’s foodsafe.

  • Ryan, I love your idea above with mixing the glaze with the stoneware slip–but, what cone did you fire the piece at? The 06 or did you go up to the stoneware cone (6 or more?)

    And, if you or anyone else could comment–I shy about only firing a piece to cone 018 to maintain the burnished effect–doesn’t this leave you with a pretty fragile piece? Certainly, you can’t use these pieces for utility–only decorative use–but still isn’t it too fragile at only 018?

  • Thanks Sumi – The directions are very clear and easy to follow. The pot with the leaves is just beautiful – I wished I could pick it up and hold it. I’ve never used oil before – I’ll try it on my next pot.

    Ryan – I want to try your idea too. Did you mix equal parts by weight or by volume when you mixed the clear glaze with casting slip?

    I wonder about adding a little soda ash to the burnishing water for shine and richness?

  • I’ll try to address a few of the questions raised above. A piece fired to cone 018 is quite fragile, and not utilitarian in any modern sense of the word, although a good red clay can be pretty hard even at cone 018. The clay I use, Navajo Wheel, is really amazingly strong at that temperature. Actually stronger than a white stoneware fired to bisque temperatures.

    The leaf pattern on the pot shown was impressed before burnishing with the serrated edge of a seashell. It is by Ian Garrett, a South African potter. The image is from my book Low-Firing and Burnishing. You can also decorate a burnished surface after burnishing by incising. Use a sharp blade to scratch through the surface of the burnish to create contrast and texture.

    I have never tried to add soda ash to the burnishing water. No harm trying. It might make the burnishing process more difficult.

  • I dig my own clay, so it’s not all refined in a factory or anything, and I wood-fired those in my small test kiln until it glowed yellow, then I slowly let the heat down by adding less wood every time. The firing lasted 2 days total. I’m fairly oldschool, but I dug that out of a local “stoneware” clay mine. I wish I had more info for you… Though come to think of it, it seemed to work out despite the seemingly low firing. You may have to experiment with it since clay bodies in different areas are not uniform. I have used it once with earthenware (same mine) clay with good results. All the clay from that mine has some grit in it… Prolly quartz or perhaps granite sand, though I’m not sure which. I’d offer to send you a sample tile, but I’m currently moving from North Carolina to Montana (USA) with the aim of going into production, and I have already taken my kiln apart and packed most of my ceramics gear. The clay body was from the Crooksville Mine in Ohio.

    Here is a picture of one of my burnished wares… This one is made from red earthenware clay from the Crooksville Mine:
    http://a7.sphotos.ak.fbcdn.net/hphotos-ak-snc4/45404_1378980646740_1598612117_30951470_3720193_n.jpg

    I dipped it in a sieved slip from the same clay body to hide the grit so it could be burnished. Then at the suggestion of a friend, I carved irregular shallow grooves in it for decoration. It was fired in said friend’s electric kiln.

  • You can use a grogged clay which will make the pot stronger in firing but you will have to burnish at leather hard so that the particles of grog are driven into the body of the pot. You may then want to put a coat of slip – works well if you are planning to use terra sigillata. This is the method we were taught by Magdelena Odundo.

  • Hi Mandy. I’m new to the ceramics scene and have read all I could lay my hands on by Magdelena Odundo. Can you please tell me (or tell me where to look for the correct information) a)exactly when does she put the coat(s) of slip on and b) when is she burnishing?

    I am doing a lot of experimenting on burnishing with and without slips at the moment but your help would be very much appreciated.
    I am very grateful to have discovered this site and have learned heaps about clay.
    I found out that we can not buy terra sig here in New Zealand as it is not imported.

  • I have been making burnished pit fired pots for 35 years. You can burnish earthenware pots with terra sigillatta and fire to 012-010 and still have the soft sheen.

  • I fire my burnished pots to cone 06 and still get a nice enough sheen. I tend to burnish at leather hard and skip the whole sanding and oiling thing. I then pitfire them with green leaves up against the pot (ferns work well), surrounded by sawdust or wood shavings. I get some remarkably detailed leaf images! To finish, I heat pots in my oven while melting wax on top the stove (in a double boiler). Apply the wax to the hot pot, inside and out, with an old brush and polish with a soft cloth as the piece cools. Beautiful, rich sheen and waterproof as well. These are my favorite pieces! Give this a try, you won’t be disappointed.

  • ria – I make my own terra sig by making a slip of ball clay (OM4 here in Canada – I don’t know what your equivalent is) and water, then letting it sit overnight and siphoning off the thin slip on top, leaving behind the coarse particles which have sunk to the bottom. The thin slip is the terra sig. I make a big batch as it keeps forever. I apply it to bone dry clay, and polish it with a chamois when it has lost it’s wetness, but before it is dry. It holds a soft sheen until cone 06. I think Vince Pitelka has a much more detailed terra sig recipe in his book, and also on-line.

  • Anne I looked at a lot of recipes, some of them so complicated you need an engineering degree and a licence for flying an aeroplane to figure it out. I gave up even before trying to make it as I hoped i could buy it – easier. Thanks for letting me know what you do – much appreciated.(Do you burnish your pots or is the terra sig doing it?)

  • Ria – When you polish the damp terra sig with a chamois it brings out the shine. that’s all you need to do. If it is too dry it will scratch instead of polishing.If it scratches just paint on a bit more terra sig. If it is too wet it will wipe off. A little practice will show you the right degree of wetness. I usually layer on several thin coats. The only caution is not to get your greenware so wet it falls apart.

    I add a little alkali water softener to deflocculate the slip before letting it settle, but I don’t know if this is necessary.

    This terra sig is white. You can add stains or oxides to colour it but it won’t be as shiny. I have tried making it with other clays. The ball clay works best in my experience, but every clay is different and has its own temperament. Experiment with what you have.

    I usually bisque my work to cone 06 and then either sawdust or pit-fire it. The clay I use is a very groggy stoneware. I tend to leave the surface a little coarse because i love the satiny terra sig over the rough texture. You can see some of it (older work) at
    annenovakart.com.

    y

  • terra sig is an ancient way of putting a gloss on pottery and was a technique used before the invention of commercial glazes. i’ve seen the gloss acheived w/o terra sig, so i question using it for decorative peices. sumi, what do you think? what is the advantage to achieving a shine with terra sig to getting one w/o it?

  • I got a lovely dullish sheen by “burnishing” a stoneware pot at leatherhard stage with a metal kidney by pushing firmly on it. The pot was then bisqued, a patina put on and rubbed/sponged off and fired to cone 04 in an electric kiln. I then put a layer of shellac over it. It looks really lovely. It has a deep ochre colour with the dark in the crevices. (Sorry I do not know how to add the picture of it)

  • I’ve been burnishing and using terra sig for years now and love the combination. My favorite results come from burnishing just past the leather hard stage with a hard object (I have used stones, spoons, a polished wooden tool, and anything else handy) then putting on a thin coat of a contrasting terra sig and burnishing this with a plastic grocery bag. The sig is semi-transparent and gives the piece an incredible patina. I’ve even mixed the terra sig with mason stains for blues and greens, although the mason stain particles are pretty course so you have to be careful. I usually then bisque to 05, and toss the piece in a smoky fire, sometimes with a slip resist that crackles, and ooolala, fun!

  • i wondered why the photos in this article looked familiar. This article and same pictures appeared in Pottery Making Illustrated Spring of 1999.
    Funny.

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