Jon Rawlings Pottery
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Sanding Pots

4/10/2014

26 Comments

 
Picture
When I first started potting, almost every potter I spoke with or read told me that sanding pots was a waste of time. Some of them even thought trimming was a waste of time and only showed that a pot had not been well thrown. I ignored all of this, maybe to my detriment. I sand all of my pots at different stages using different materials and techniques. Most pots only need a light sanding around the foot to smooth them out. A smaller number need more extensive sanding. 

The main reason I wrote this blog was because of what I saw at HPG all of the time: potters who were struggling to smooth their bisqued or glaze fired pots using garnet or emery sandpaper, the sort of sandpaper most people use on wood or metal. They'd be holding their pots over a trash can and sanding away all morning but never really smoothing the surface as well as they wanted. These sandpapers might be okay for sanding greenware (though green scrub pads are probably better), but they're not efficient at smoothing bisqued or glazed pots. Another reason I wrote it was because of what I saw too often at pottery sales: customers who wouldn't buy pots because their surfaces, especially their bottom surfaces, were too rough. They didn't want pots that would scratch their tables or pianos. What I heard most often were comments from customers about pots that were "not finished well," "poor craftsmanship," and the like. Why lose sales like this when it's so easy to smooth the bottom of a pot?

The image above has several things I use to sand pots. The first two on the left are silicon carbide dry wall sanding screens made by Gator (www.gatorfinishing.com). The larger is half of a sanding screen that I cut with scissors and the other is a small piece I cut for sanding hard to get at places. Silicon carbide works so well on bisqued and glaze fired ceramics because it's so tough. Kiln shelves are made of the same material. Next is a green 3M scrub pad, the sort of thing you can buy at any grocery store. When these scrub pads are new, they're thick and stiff, useful for sanding large areas. After these pads have been used for awhile, they become thin and flexible and useful for sanding delicate areas like rims and anything that's been carved. The sandpaper on the far right is silicon carbide sandpaper made by Gator and especially good at giving more coarsely sanded pots a silky finish. 

I use 80, 120, and 220 grade silicon carbide sanding screens to sand bisqued or glaze fired pots where they need it. If I only want to sand the bottom of a glaze fired piece, I grab an 80 grit sanding screen and the bottom of any pot is smooth in about 10 seconds. I don't care if it's Soldate 60, Rod's Bod, or Death Valley, every one of these groggy clays will be smooth in about 10 seconds if I use a silicon carbide sanding screen. You can achieve the same result with silicon carbide sandpaper, but the sandpaper wears out quickly so you go through several pieces of sandpaper before achieving the smoothness you want. Sanding screens are tougher and can be used several times before they're worn out. If I want to sand the outside of a bowl and make it as smooth as possible, I'll use the sanding screens first and then go to 320, 400, and 600 grit silicon carbide sandpaper. I started out using pieces of silicon carbide kiln shelves to smooth the bottoms of pots or even the sides of bowls, but I ended up chipping the edges too many times and the sound of a kiln shelf smoothing the side of a bowl is worse than fingernails dragging across a blackboard.

I sand stoneware differently than I sand porcelain. I sand green stoneware as little as possible before bisquing it, usually only around the edge of the foot and rim. If I sand large areas of a stoneware pot with green pads or a screen, it roughens the surface and makes it less smooth because it loosens the grog which rips through the soft clay. Of course, if that's the effect you're after then go for it! I usually don't sand bisqued stoneware at all unless I notice it has sharp edges. I've found that if edges are too sharp, they tend to chip in the glaze firing. After stoneware pots are fired to cone 10, I use a sanding screen, usually 80 grit, to smooth the bottom of the foot. If there are large areas of bare clay that are exposed like on the outside of bowls, I use the sanding screens to smooth the surface and then switch to sandpaper. If I want a super smooth surface, I'll use water with the sandpaper. 

With green porcelain (or porcelainous clay like BMix), I usually sand the whole pot when it's completely dry with green scrub pads. If the pot needs extensive sanding, I'll start with an 80 grit silicon carbide sanding screen to remove material more quickly and then use a green scrub pad to make the surface smoother. I keep my pads for porcelain separate from my pads for stoneware so I get as little spotting on my porcelain as possible. But if I happen to get a spot or two from some impurity, I consider it a "beauty spot." I only sand bisqued porcelain if it has edges that are too sharp. I've made quite a few porcelain pieces that have no glaze on them at all. After they come out of the cone 10 firing, I do not sand them with silicon carbide sanding screens because they tend to leave marks on the surface that are hard to sand out. I start with 320 silicon carbide sandpaper, then 400, and finish with 600. By the time I'm finished, the surface of the clay has a satiny texture. You can always go farther than this by using diamond-embedded pads that go up to 3000 grit or higher, but I've never been able to feel the difference past 600, even on porcelain. 

If a piece is carved, whether it's stoneware or porcelain, I'll sand the carving very carefully with a worn and flexible piece of green scrub pad. I don't try to do too much of this, but I concentrate on places where I think the finished pot might have sharp edges, especially with porcelain. I've found that I'm more apt to knock pieces off at this stage and it's also unnecessary to make the surface perfectly smooth. Most of it will be covered by glazes and the uneven edges often make the glazes break in more interesting ways. If I feel the need to do more sanding on places I've carved, I'll wait til the piece has been bisqued and then use a white sharpening rod whose corners have been rounded (not pictured) to remove more material. 
I've found that when I sand greenware pots, I have to thoroughly wash them after they've been bisqued and then let them dry completely before glazing. If a piece has been sanded, clay dust is all over the pot, even if you've been careful to remove as much as possible. I pay close attention to pots that are carved since clay dust settles in crevices and I always use a toothbrush to get it out. If you don't get all of the dust off a pot, you'll have plenty of glaze problems later.

Safety is an important concern when you're sanding pots. Doing it over a garbage can or a bowl of water doesn't help. Sure, large particles of clay dust will fall in the garbage can or in the water, but we should all be more aware of the really fine clay dust that will stay suspended in the air for up to 2 days and can end up in our lungs and the unsuspecting lungs of our friends. When I sand pots, I'm always outside and a good distance from the studio. (Okay, that's easier to do in January when you live in Hawaii!) I wear a mask to protect myself, the same mask I use for spraying pieces that's minimally adequate: 3M N95. I don't take off my mask to blow dust off the piece. I use a soft brush to do that and use a damp sponge to take off the rest. I use the same brush and sponge to take dust off my clothes and I wash my hands and arms with soap and water when I go back into the studio. I clean my apron regularly. Do whatever you can to minimize clay dust in the air.  

The final observation I'll make is to be very careful how you handle your pieces when you sand them, especially when you sand greenware. Be aware of every part of your body and how it should touch the clay. Just two days ago I was sanding a bowl that I'd carved. I was trying out a new pattern around the rim and was pleased with how it looked. I'd successfully trimmed the foot which is always tricky to do without knocking something off. I let it dry a few more days while covered, and then I started to sand it just a little. When I turned the bowl over to sand the foot a bit (something I've done many times), the rim hit my forearm and knocked a 6-inch piece off. Had to recycle the whole thing. If you do turn a bowl upside down to sand it, make sure the fingers of your hand are spread out widely enough so it doesn't move when you turn it over. So make sure you really think about what you're doing every time you sand a piece and CONCENTRATE!











26 Comments
mary
9/24/2015 12:21:42 pm

do you mind me asking what you use to catch the dust? we dry sand all of our pieces in doors and are looking for a system to catch the dust. thanks!

Reply
Jon
9/24/2015 10:54:14 pm

Thanks for your question, Mary. I sand everything outside and the wind blows it away. I always wear a mask when sanding to protect myself from the dust that's swirling around. I do see people sanding pots inside at the Hawaii Potters Guild. They always do it over a large trash can and away from everyone else. I'm sure there's a better way of doing this, but let me ask around and I'll get back to you.

Reply
mary
6/4/2016 03:50:36 pm

If I sand greenware, I set a large bowl of water on a stool so I don't have to stoop or lean right over. The dust falls into the water which means less dust floating around, I also wear a mask. I keep another bowl of water and cloth nearby to wet wipe the area.

Reply
mary
9/28/2015 08:56:42 pm

thank you so much!

Reply
Terry Granade
1/2/2017 07:16:15 pm

Mary,
I hope you're still writing on this. My wife and I just installed a water feature in our back area. Texas Hill Country. Our jar is a Spanish pot with a pattern encompassing the outsude of the jar about 1/3 way down. When the water flows down the side, in 2 areas, the elevated design, sprays the water farther out than the rest if the jar.
Now,
1. what should I use to sand the design down, so the water flows more evenly over the sides of the jar?
2. Is it possible to sand the lip of the jar, so the lip is more even at the top?

Thank you,
Mahalo
Terry Granade

Reply
Terry Granade
1/2/2017 09:17:35 pm

Jon,
I errored and addressed my question to Mary. So Sorry.
The questios still stand. I can forward a pic if you'd like?
Terry Granade

Reply
Jon Rawlings
1/2/2017 11:13:32 pm

Because you described your pot as "Spanish," I would guess that it's made of red or buff terra cotta or earthenware which would be relatively soft compared to high fired stoneware. If you have a small amount of material to remove from the design on the side and the lip of the jar, my first choice would be to sand it down with a dremel. I wouldn't use a dremel on high fired stoneware, but it should work great on terra cotta and will give you the accuracy and control you need so you don't damage the rest of the jar. If you don't have access to a dremel, you can try using silicon carbide sanding screens, but I would cut them small enough so they don't wreck the rest of your pot. Sounds like you have a great pot; just needs some fine tuning on the design. Please let me know how this goes for you.

Reply
Elizabeth
4/12/2017 07:56:51 pm

Can you ever sand a really rough pitted, Bubbly glaze? The pot and and glaze look cool but feel like pumice. Thanks

Reply
Jon Rawlings
4/12/2017 09:07:13 pm

It's funny that you asked that question today. A lady showed me a raku vase today at the Hawaii Potters Guild that had small bubbles over its entire surface. She asked me if she should break the bubbles and sand it a little. I picked up the vase and the bubbles were so fragile that a bunch of them broke and cut my hands in several places. Nothing serious, but it took me awhile to get the glass out of the wounds. I suggested that all bubbles be broken as safely as possible, maybe with a metal rod or a piece of kiln shelf, and then sanded just a little to take off the sharp edges. Some potters like Gertrude and Otto Natzler purposely created bubbly surfaces. They would break the bubbles to create a crater-like effect. I wouldn't do this with any vessel that would contain food. I've had a number of small bowls that had bubbles on the inside. If I refired them and they still had bubbles, I threw them away. I don't want any broken glass in someone's food. I've had several large bowls that had bubbles at the bottom and I've just broken the bubbles with part of a kiln shelf and then sanded them a little. Make sure there are no sharp edges or places where the glaze might easily break off. If you're not sure, better to throw the piece away. If I do keep pieces like this for sale, I put separate labels next to the price tags alerting buyers that they are not food safe and are only for decorative use. Please let me know if you'd like to dialogue more about this issue. It's important because we should always be thinking about the safety of the people who use our pots. Thanks for your interest!

Reply
Shirley Zussman
10/29/2017 09:38:19 am

I made a covered candy dish, and meticulously worked to make sure that they lid would fit properly. I allowed it to dry slowly, checked again when it was leather hard and adjusted anything that I thought would prevent it from fitting once it was fired. I used underglaze on the greenware, and it wasn't until I did the final glaze and it was fired separately that the lid no longer fit. I have been sanding it, hoping to salvage a piece I spent so much time on, but am getting no where fast. It still doesn't fit. Do you have any suggestions? Thank you!!

Reply
Jon Rawlings
10/29/2017 09:14:25 pm

Thanks for the question, Shirley. For next time I would make sure to fire the lid with the pot. Pots not only shrink when they are fired, they also change shape, sometimes quite a bit. A candy dish like this might go a little more oval, for instance. If a lid is in place, it would be more likely to retain its original shape. In this situation, sanding is not going to remove enough material for the lid and pot to fit together. If you have access to a grinder, you can try reshaping the lid. Go slowly and remove just a little material at a time until you get the right fit. When you use a grinder, it's easy to remove too much material quite quickly or to chip off large pieces. Another option is to use a dremel with a silicon carbide bit. This is more time consuming but can also work. Again, I would try to reshape the lid to make that fit in the pot. Please let me know how things work out for you. I know what it's like to work hard on a pot, to like the results but also need to change something to make it functional.

Reply
Shirley Zussman
10/30/2017 05:16:46 am

Thank you so much for your explanation. It is really helpful. My teacher told me that the pieces had to be fired separately, probably because he feared they might get stuck. I had been so careful to make sure that they fit...but you are so right: they change shape -- quite a bit! I have been working with sandpaper to remove the 'offending' material, but, as you say, it is not proving to be enough to fit together. I don't have access to a grinder, and may just abandon this project -- and just try to learn from it. I will try to ensure that the coil I put inside the lid is MUCH farther from the edge so that this doesn't happen. I hope that others reading this can learn from my experience.

Sally
2/17/2018 08:22:42 pm

Thanks for this great info Jon. Are you sanding by hand or do you use a grinder or other mechanical advantage? I have seen people stick sandpaper to their wheel head and have been suggested to use a deburring wheel on a grinder, so I'm a bit overwhelmed with choices and info.

Reply
Jon Rawlings
2/17/2018 11:04:28 pm

I'm sanding by hand and I would suggest doing that to begin. I know people who use a sanding pad they attach to their wheel and others who use a grinder, but they use them to make the base of their pot perfectly flat, not just to smooth out the bottom. Try starting with something simple and less expensive like a silicon carbide sanding screen and try these other techniques later if you think they'd be helpful. Let me know if you have any other questions or need some clarification. Good luck!

Reply
susan
4/3/2018 11:18:43 am

Thank you a million times over. I appreciate you sharing. Sanding on bisque pottery, who knew. I am happy with the results. Used the green scrub pad and followed up with a emery board used for fingernails. Super - thanks again.

Reply
Nirupa Varatharasan
10/4/2018 08:43:04 am

Hi, what would you suggest I use to sand glaze drips/sharp points on glazed porcelain? Thanks

Reply
Jon
10/6/2018 11:55:04 am

It depends on how much material you need to remove. Silicon carbide sanding screens or sanding paper is fine if you just need to smooth something out just a little. If you need to remove more material, I would suggest using a dremel with a silicon carbide bit. You can find these bits at Amazon. They come in different shapes and don't cost very much. Let me know if you'd like more information or clarification. Thanks for your question!

Reply
Deena
1/20/2019 01:20:47 pm

Hi. I made some hand built Nerikomi pieces with cone 5 porcelain and mason stains. Invariably, some of the surface got smudgy. They are thin and very delicate so after I bisque them, I think I will need to lightly sand them to bring out the pattern. Can you recommend which material you would recommend I sand with? Thank you and I will be sure to take safety precautions when sanding.

Reply
Don Allen link
7/4/2019 11:17:33 am

I've been sanding pottery for 2 1/2 years. The entire gamut. Pots of all sizes and shapes, trivets, mugs, tankards and all the ovenware of harder fired material such as platters, small and large rounds. I use 60 grit for the stoneware on an orbital. Leaves the foot nice and smooth. The platters also get used on 60 grit and I leave the edges round and smooth. No burrs, no roughness. I want it PERFECTLY smooth. Some of these platters are huge, same with casserole dishes and large bowls.

On the soft stuff like cups, bowls, plates, I use 80 grit. Finding the right balance between stiffness of the paper and cost as sandpaper and really GOOD sandpaper is expensive. I can do 16 large coffee mugs with ONE piece of 80 grit, that is taped together. That's a stiffer paper and the oxide is good and tight. If you're really good and have a light touch, a good orbital with #80 grit can clean up the slip on the back of plates and the foot extremely fast. I finish up by hand.

Reply
Penny Ritzman
12/10/2019 10:39:52 am

I just fired a lidded casserole dish in the kiln -- when I pulled it from the kiln, there was a small spot where glaze fused the lid and pot together. I was able to separate them without much issue, but there's about an inch long chip underneath the lid rim where the glaze stuck to the pot bottom. Is this still usable? Should I sand the chipped area smooth? I will be dremeling off the tiny piece of glaze stuck to the pot rim. Or is it better to throw it away and not use it?

Reply
Rohan bhansali link
12/16/2019 10:12:27 pm

Abrasive Garnet Sand, Garnet 80 mesh, <a href="http://abrasivegarnet.in/garnet-30-60-mesh/">Garnet 30/60 mesh</a>, Garnet Sand, Exporter, Manufacturer, Supplier in several country like Ajman, Brazil, Canada, Colombia, Denmark, Dubai, Egypt, Kuwait, Iran, Iraq, Ireland, Israel, Jordan, Sudan, United Arab Emirates(UAE) at low price with best quality. Abrasive garnet sand used as an abrasive media.

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Masako K Jankovsky
3/23/2020 04:32:55 pm

I feel GREAT that I found your website. Your pottery is beautiful, and your website is so well organized. During this Covid-19 pandemic, I found something to work on!! I will read your web to learn about your ceramics!! ( I just started to take Ceramic class last fall, and got stuck. I am like a kid playing in the Magical Sand-Box!!) I can easily forget time . ) Thank you so much for the great Website!!

Reply
Arden Katz link
8/18/2020 11:02:07 am

Hi, this is a great site. I hand build and use molds for plates, platters, etc. the backside of my fired paper porcelain is pretty smooth. I like the idea of making it smoother to give almost that shiny look. So you have given enough info. regarding what to use. If some plates, etc. look visually smooth is it necessary to sand? You can get paper porcelain very smooth when working with it. Hope to hear from you soon. Thank you. Arden katz

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Jules link
12/23/2020 12:15:17 pm

Very nice bblog you have here

Reply
Jessica Dsouza
1/25/2022 11:01:21 pm

Hii Jon,
I'd like to get some advice from you about my pot.. I want to paint it but I'm not sure how to get started. I read that sanding is important to help the acrylic paint stick but my pot has designs on it and I think maybe sanding it would erode the design. I'm not sure where to proceed from here. Can I please get some advice

Reply
jameslehner992 link
6/20/2022 06:06:39 am

Your way of sharing experience is very joyful. Keep sharing.

Reply



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