To be updated.
Throwing large pieces on plaster bats reduces cracking issues.
Using chamois leather to attach a plaster bat to the wheel
Large sheets of chamois leather for drying cars can be purchased online very cheaply. Synthetic versions that I have tried do not work.
I use X-acto blades all the time, some modified for specific tasks like carving porcelain or scraping glaze off of feet.
I’m not sure if it’s all part of a vast X-acto conspiracy, but it seems that a lot of people don’t know that these blades can be easily & quickly sharpened? While there are a number of sharpening methods (even just using bare fired porcelain) that will work, it can be tedious to get the sharpening angle right. The most convenient method I have found is an angled sharpener (pictured). Just a few quick passes through the ceramic sharpener gets the blades useable again. It’s faster for me to sharpen the blade than switch out a dull blade for a new one. (Unfortunately my sharpener is approximately 45% degree sharpening angle (> 20 degrees per side), it might be better to have a narrower-angled sharpener.)
Also note that not all X-acto blades are stainless steel. You don’t want rusty blades all over your studio or in your reclaim. A 10 or 100-pack of stainless steel #11 blades might last you a lifetime.
A step up from the X-acto blades are stainless steel surgical blades. They come in a wide variety of shapes and sixes perfect for a number of jobs. I usually use the blades without a handle. They come in ten-packs and last a really long time if you sharpen them.
I’m sure that using a garden watering can for pouring glazes is a common technique, but when I came up with the idea I thought I was a genius 🙂 The design of a watering can ensures a constant, strong stream of liquid during pouring that is perfect for glazing. Bubbles are reduced since the watering can pours liquid from the bottom of the can.
Pouring the Outside
Once the inside is glazed, I will wait until the next day to glaze the outsides. It’s important not to overload the bisque ware with water.
I use an old electric wheel for pouring the outsides. It’s important to rotate the wheel at sufficient speed so that glaze does not gather on the inside rim of the pot.
I’ve finally gotten a new low-fire electric kiln. This kiln is designed to fire up to 1000°C, so it’s useful only for on-glaze enamels and bisque. Total cost was 2900RMB, which is about $420USD.
I have a couple “wet boxes”. These are plastic bins with lids into which a layer of plaster has been poured. The plaster is kept wet in order to maintain humidty, slowing (if not stopping) the drying process.
However, I haven’t used the wet boxes in a long time. I’ve found it much easier and more convenient to simply wrap each piece in it’s own plastic trash bag. Pieces stored in this manner can be trimmed weeks or even months later.
This page is in progress and will cover my kiln and firing. For now it is just a place to store my notes.
Using a Dremel or similar tool, edges of both thin and thick razors can be ground for specific uses, like scraping glaze off these plate feet.
Last year I purchased a USB microscope (see article). It’s pretty fun, but ultimately I was really disappointed by the quality of the images. The 5MP sensor seems pretty cheap and images have a lot of artifacts. Furthermore I was never satisfied with the color.
The best choice would probably be a “real” microscope with a camera adapter. However, this little hobby of mine doesn’t justify spending a lot of cash.
There are a few tutorials online for creating your own phone microscope using the lens of a laser pointer. (I tried this and it worked pretty well, but I never found a way to conveniently attach the lens to the camera.) Wired’s article Turn Your Cellphone Into a High-Powered Scientific Microscope has a good tutorial as well as background on the scientists who are using cellphones as biomedical devices.
Fortunately there are now multiple products for sale that make it easier to attach a lens to the phone.
There’s a former Kickstarter project that looks promising and is shipping, the 15x Micro Phone Lens and 150x Micro Phone Lens. (See my November 2016 update, below.) In China there are a number of cheap alternatives.
Supereyes Smartphone Microscope (Not recommended)
I purchased the Supereyes Smartphone Microscope for about $7USD. The images below were taken with this lens. Unfortunately the top of the plastic lens is not protected and I scratched it after playing with it for less than an hour.
The images from the iPhone with attached lens look much better than my USB microscope. The photos below were taken in natural light.
Microphonelens 8x Macro & 15x Micro Lens
On a recent trip to the US I ordered the Microphonelens 8x Macro lens and 15x Micro lens. These lenses are different than others- they simply stick to the phone’s camera lens and have no outer support column.
In use, I found it more difficult than the other lenses because I could not directly rest the lens at the correct distance against the viewed object, resulting in more blurry photos due to camera shake. Also, while the micro lens is designed to stick on the phone lens it falls off if touched and gets dirty in the process of handling.
These drawbacks are forgivable, though, as the quality of the images seems superior to either of the other lenses I tested. Also, the lens cleans up easily with just a bit of pure or soapy water. The soft material also scratches less easily than hard plastic lenses.
For viewing glazes, both the 8x and 15x lenses are useful. I would recommend the 15x (although of course it has a narrower depth of field).
Spraying glaze is a fairly complicated process. There are craftspeople in Jingdezhen whose only job is going from workshop to workshop spraying glaze. There are so many factors involved with spraying (the type of work, thickness of work, type of glaze, glaze consistency, air pressure, spray head type, even weather) that it requires years of experience to be able to master the art.
I hope to slowly add to this article in the future. For now I will just lay out the basics of how I spray glaze.
The Spraying Booth
My spray booth is made locally in Jingdezhen. It’s a simple stainless steel frame with glass. A large fan is attached to the back, sucking out particles. Water is pumped from a bucket through a hose that leads to the top of the booth interior. The water is channelled along the top of the glass and then exits through small holes, forcing the water to run down the glass, washing away glaze. The water finally exits through a hole in the bottom of the spray booth, pouring back into the water bucket.
The Air Compressor
I have an old, noisy air-tank compressor that I rarely use. I much prefer the Jingdezhen method- a cheap magnetic air compressor used in fish tanks. I’ve used my current compressor for six years and it still runs great, with no need to worry about adding oil or filtering the outgoing air.
I’ve found that a 520W compressor is ideal. In the past I had a smaller compressor that didn’t spray as well.
The sprayer does a great job of mimicking traditional Jingdezhen glaze spraying using just the breath. A normal air compressor using a paint sprayer head will give you a finely atomized cloud of glaze resulting in a powdery glaze application. But a traditional mouth sprayer connected to the fish tank compressor will give you relatively large glaze droplets that soak into the clay, leaving a more compact glaze application.
The fish tank compressor method also sprays less glaze into the air. I often just run the water pump and leave the booth fan off (but of course I wear a good respirator).
Note that this type of spraying results in more water being absorbed into the ware. Especially for thin pieces, care needs to be taken not to overload the ware with water. I usually spray the outsides one day and the insides the next, giving the ware sufficient drying time in-between sprays.
If while spraying you notice the glaze stays wet and shiny on the surface it means you are either spraying too close or have already reached saturation. This is bad. There’s a good chance that the entire glaze layer will separate from the ware.
The glaze sprayers widely used in Jingdezhen were originally meant to be sprayed using only one’s mouth. Since then, the mouth stem has been modified from conical (larger end towards mouth) to tapered at both ends for a tight fit into an air compressor hose.
Making these sprayers is a specialized craft. The sprayers come in dozens of different configurations. The sizes of the container, nozzle, and mouth stem as well as the distances between these parts, all determine the characteristics of the spray pattern. In general, larger containers are used for larger work (e.g. sculpture), while the smallest containers are used for spraying underglazes and details.
The Paasche L Sprayer #4
Like Jingdezhen glaze canisters, the Paasche allows you to make fine adjustments in distance between the nozzle and container tube. Along with adjusting air pressure and glaze thickness, a number of different spray patterns can be achieved.
It’s difficult to write about actually spraying glaze, because each session is different. The basic process is:
- Spray outsides. Do not rest ware directly on turntable or plaster disc, but rather elevate it with a stable item such as a smaller plaster column. If the inside is already glazed, on top of the support you can add a sponge disk.
- After spraying the bottom, you can scrape glaze off of the feet.
- Ideally, wait one day while the bottoms dry completely. If in a rush, blow air over the ware with a fan.
- Spray insides. Take care that feet are not resting on a surface that will become wet during glazing. The dry plaster turntable disk helps with this issue.
- Clean glaze off the feet by trimming or with a sponge.
- Using a notch in the turntable disk as a guide, keep a mental note of how many revolutions you make and the resulting thickness of the glaze (checked by scraping). The number of revolutions will vary each glaze session, and is influenced by the glaze canister, air pressure, glaze consistency, size of ware, etc.
- Keep the glaze canister in constant, steady motion- up & down, side to side, or circular. You may need to vary the motion to get consistent application.
It’s important to wear a NIOSH certified mask whenever using dry glaze materials.
I guess mixing up glazes isn’t that big of a deal, but I’m sharing my technique just in case there are some absolute beginners out there.
I find it easier to use a digital scale, see my article here.
Glazes “don’t travel well”, in other words materials, application, and firings vary from studio to studio. Even for well-known glazes, it’s important to first make a small tests. For these tests, I use 50g or 100g of material and apply the test glaze to a number of different clay bodies.
I use the Glazy Batch Calculator on my phone which will show you the subtotals for arbitrary amounts of total glaze materials.
Once I’m happy with a test, I mix up a larger batch of 1-2Kg. 1Kg is enough material to glaze small cups, 2Kg is a good amount for small bowls. These larger tests should reveal any problems with glaze suspension (is bentonite required?), application (cracking, peeling, etc.), and fired glaze defects. Once you have some nice results with 1Kg, you can finally move on to a big bucket of 5-10Kg.
Mixing up a test
Flat test tiles require the least amount of glaze for application. Here’s my article about how I make test tiles.
Sieve Mesh Size
For “natural” glazes containing large-grained materials or ashes, or in cases where homogeneity is not a concern, it’s fine to use a larger screen of 60-80 mesh. But in all other cases I use 120 mesh or smaller. Small mesh size is very important for glazes that contain small amounts of very important materials such as coloring oxides (e.g. cobalt and iron). But it’s also important to ensure that materials are adequately broken up and mixed (such as clays).
Below you can see two tests of the same batch of glaze fired in the same kiln. The glaze on the left was applied after passing the materials three times through an 80 mesh screen. The glaze on the right is the result of passing that same glaze once more through a 120 mesh screen.
Poorly dispersed colorants like iron are easy to see in fired glazes. But keep in mind that other “invisible” glaze ingredients like clays, feldspar, etc. also need to be well-dispersed and mixed in order to ensure the glaze melts properly. If you use a 60-mesh screen for tests and then a 120-mesh screen for large glaze batches, there will be differences between the fired results.
I’ve seen a few techniques for seeing into the kiln at high temperature. An old friend of mine still prefers blowing into the peephole, unfortunately on more than one occasion it has resulted in the particles resting in the peephole to be blown in as well, settling on the ware. The Jingdezhen firing masters I’ve met just put on an old pair of sunglasses and squint (on the rare occasions they actually need to look at a cone).
I’m currently using #5 welding goggles, the only pair I could find for sale here but they work really well. If you have a choice, go for IR rated lenses which protect from harmful infrared light. Here’s a really good article about eyeware for potters.
Combined with the goggles, a strong flashlight will give you a really good view inside the kiln. This year, my old LED flashlight finally gave out, and at around 400 lumens it was still a little difficult to see in the kiln. The LED flashlight I purchased as a replacement was on sale for about $40USD, a little expensive but to be honest I just wanted to know what 2000 lumens would look like. It’s blinding! But using this flashlight I can see all the way to the back of the kiln even in reduction at 1300° C (my kiln is only 1 meter long). You can even see glazes start to glisten in the light of the flashlight as they begin to melt..
So if you’re getting a new flashlight for the kiln, I think you should go for at least 1000 lumens.
Yaoli Ancient Village (瑶里古镇) is a fairly well-known tourist destination located about 1 1/2 hours by car from Jingdezhen.
During the past few years I have visited the village a handful of times, and each time I’m even more disappointed by the continuous development, poor management, and flocks of tourists.
But the countryside around Yaoli is beautiful. If you continue driving past the ancient village you will find numerous small villages with restaurants offering local cuisine. Drive up the mountain and you should come across wonderful views of the valleys as well as waterfalls.
Yaoli is also the home of a type of porcelain stone known as “glaze stone”. This stone is a major component of traditional Jingdezhen glazes.
There is a very nice outdoor museum in Yaoli called Raonan (绕南陶瓷主题园区) which runs along a small river. The river powers hammer mills that continuously crush Yaoli porcelain stone. There are also ancient dragon kilns and even pottery wheels where you can try throwing Jingdezhen porcelain.
After years of using simple balance scales to measure out glazes, I finally decided to invest in a better setup. I couldn’t find any triple-beam scales for sale in Jingdezhen, so instead I purchased a cheap 200-gram digital scale from a local shop. I was delighted at how much simpler and faster it was to mix up tests with the digital scale. It was only a few months later when I compared the digital scale to my old balance scales and discovered that the digital scale was consistently inaccurate, even just after calibration.
After having wasted 600RMB, I decided to just buy the best reasonably priced scales I could find. The only imported brand in my price range and available in China was the Ohaus Scout Pro line. I purchased two- one for tests and measuring colorants (model SP202, up to 200 grams with 0.01 gram readability) and one for mixing up bigger batches of glaze (model SP4001, up to 4000 grams with 0.1 gram readability).
The SP202 is very accurate, great for when you are making very small test batches. The scale can also be used to measure colorants for big batches of glaze.
I use the SP4001 to directly measure out 1-3kg batches of glaze, or for measuring out each ingredient in larger glaze batches.
After a couple years, the Ohaus scales are still performing very well, especially considering that they are stored on the glazing patio and subjected to the weather. The scales cost me much more than I wanted to spend, but they are well worth the money.
- If you’re looking to purchase scales for small glaze batches but don’t have a lot of money to spend, go for a triple-beam scale. A good triple-beam will be much more trustworthy than a cheap digital scale.
- If you only have enough money to buy one digital scale, get a 200-gram scale, preferably with .01 readability. This will allow you to make accurate test glazes, as well as accurate colorant additions to larger batches of glazes.
- If you do buy a digital scale, don’t forget you will need to calibrate it from time to time. (I do so each glaze-making session.) You will need accurate calibration weights in order to so, adding to the final cost.
Note: In the following photographs I only used the most basic lighting setups. Even using natural light, you can take advantage of reflectors to highlight shadows and produce fill light. Try searching “product photography lighting” if you are looking for information about advanced lighting.
The PBS Art21 documentary episode “Memory” contains a segment about Japanese photographer Hiroshi Sugimoto. Sugimoto gives a tour of his photography studio which is surprisingly simple. No fancy lights. Just a camera, table, and backdrop placed near his studio window. Sugimoto controls the lighting simply by rolling the window shade up and down.
If you are not worried about lighting consistency from photograph to photograph, taking pictures of your artwork using natural light is the simplest approach. You can wait for a cloudy day and shoot outside for diffuse, cool light, or use window light. If you do not want a color cast, simply use a grey card.
Grey cards provide you with a reference neutral grey. This grey can be used in photo editing software like Photoshop and Lightroom to correct for color temperature casts. The grey card I use is X-rite ColorChecker Grayscale because it also provides a white and black reference which helps adjusting exposure and black/white levels.
You might be tempted to use a sheet of paper, piece of styrofoam, or other object as a cheap reference with which to set white balance. But in my experience, it’s much better to buy a professional grey scale card. Even with something as “standard” as a piece of paper, the color differs between brands and thicknesses.
Below are three photos taken with the same lens, ISO, white balance setting (Auto), shutter, and speed. In Lightroom I only adjusted the white balance.
Remember there is no “correct” color temperature. You may prefer the cool window light, or the golden tones of late afternoon light. The grey card is simply a reference.
Color Calibration Target
Much like a grey card provides an accurate grey, a color calibration target provides an accurate reference for colors. I use the X-Rite ColorChecker and ColorChecker Passport. Unfortunately, I’m not professional enough to give you a detailed explanation of exactly how it works. All I know is that it standardizes colors in an image profile, compensating for differences in color between camera manufacturers and lighting conditions, resulting in a more accurate photograph.
I’ve made the ColorChecker part of my workflow. Every time I shoot, I include the ColorChecker in at least one of the photos, so that later I can use that image as a reference. The ColorChecker software creates a DNG profile that can be used with Lightroom and Photoshop, simplifying the workflow considerably.
Even if you are just an amateur photographer like me, I highly recommend getting a color calibration target and including it in your photos. The ColorChecker includes grey patches, so you can use it for simple white balancing as well.
There are times when you require lighting consistency (for instance when publishing a book or website) or a specific lighting setup. As most of us are not professional photographers, the simplest lighting solution in this case is continuous lighting. Just like normal room lighting, continuous lighting is simply switched on. The lights can then be easily positioned for the lighting you prefer. The most affordable continuous lighting consists of fluorescent lightbulbs mounted in a fixture that is usually surrounded by a softbox.
Below is one of my softboxes which I purchased from a cheap Chinese manufacturer.
As a beginning photographer, I was very concerned about color temperature, purchasing only light bulbs which were 5500K. (See Color Temperature.) Somehow I came under the impression that a specific Kelvin temperature rating was the sign of quality. So I was always puzzled when the colors in my photographs weren’t as rich and vibrant as the artworks themselves.
I later came to realize that the Kelvin temperature is perhaps the least important of factors to consider when purchasing lights. Just as with natural lighting, color temperature can be easily adjusted in software like Photoshop and Lightroom. And using a grey card it’s very simple to achieve a neutral white balance.
In China, restaurants are often lit with cheap, bright fluorescent tubes. It’s possible people here are not very concerned with lighting, but I find it unappetizing and unromantic to see food and people lit like this. It’s not just the brightness, it’s also the quality of the light.
My cheap photography softboxes put out a similar kind of ghostly light. Sure, they are 5500K, similar to noon daylight. But just like in a typical Chinese restaurant, colors look lifeless.
Color Rendering Index (CRI)
When I finally learned about Color Rendering Index, everything made sense. From the Wikipedia article:
A color rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with an ideal or natural light source.
Where I had been looking for light sources with a specific Kelvin rating, I should have been much more concerned with their CRI rating.
Searching through the Chinese commerce site Taobao, while almost all of the cheaper photography lighting companies tout their bulb’s color temperature, none of them even mentioned CRI. So I decided to find a bulb with a high CRI in order to compare.
Philips Master Graphica 36W/950
The only affordable high-CRI light source I could find in China is the Philips Master Graphica 36W/950. This tube is frequently used in painter’s studios to provide conditions similar to true daylight. This tube’s color temperature is 5300K (a little warmer than the typical photography light) and the CRI is 97 (very high).
As a first test, I used a Philips double light fixture and placed it above my work desk and used it at night. (Up until then I had only used cheap fluorescent bulbs in my studio.) The difference was startling. Working at night has always been a bit depressing, but the Graphica light changed the entire atmosphere of the room. It’s a really beautiful light.
Convinced that I was on the right track, I next tried taking some photographs with my old lights and then the Graphica as the light source. With the exact same shooting conditions there were still subtle differences in the final photograph. The colors under Graphica lighting just seemed richer.
Below you can see a comparison of my regular, cheap fluorescent lights with the Graphica tubes. (The large image can be rolled over to switch between the two images.) Apart from the lighting, both photos were taken using the exact same conditions. In Lightroom, I only set the ColorChecker profile and adjusted white balance.
DIY Fluorescent Photography Light Fixture
I discovered that many photographers are already using fluorescent lights for photography. In particular, this tutorial by Joe Edelman shows how to make your own fluorescent light tube fixtures for photography. I made a similar version using parts that I could find on Taobao. Because I could not find 4 or 6-tube light fixtures, I mounted two 2-tube fixtures onto a sheet metal corrugated shelving. The corrugated sheet is light, sturdy, and convenient.
In total I made four of these four-tube fixtures. This is because I also help friends photograph their large ceramic paintings, and we need lighting longer than the 1.2 meters of the 36W tubes.
For the photo of ceramics below, I used two four-tube fixtures as the side lighting. In front of the fixtures I hung a sheet of translucent softbox fabric.
Ideally, each light fixture should have six 36W tubes. Four tubes still seems a little dark for studio photography.
Scroll over the image to switch between my regular photography lights and the Graphica tube lights.
Photographing Paintings and Porcelain Tiles
Part of the reason for building the DIY fluorescent lights is to help my porcelain painter friends photograph their work. In the past they used natural light on cloudy days or my cheap softboxes. But with either of these methods it is very difficult to get consistent light over the entire length of a porcelain tile. A one meter square softbox will not illuminate a one meter long painting evenly, as the light intensity of the softbox decreases toward the edges.
The best way to photograph a flat reflective surface is to position two lights at either side, hitting the target at an angle of 45 degrees. The lights are moved away from the painting until the lights’ reflections are no longer visible through the camera.
In the session below, the lights were placed about 1.5 meters away from the subject.
High-dynamic-range (HDR) Test
You might have seen HDR images before on the internet, they were very popular for a time. Often, HDR images appear gaudy, ghostly and surreal. But HDR doesn’t have to look like that!
All digital cameras have limited dynamic range. That is, they can only record a certain range of light to dark in a photograph. HDR is simply taking multiple exposures of the same scene and combining them in order to get greater dynamic range.
For example, looking at the group of ceramics I photographed above you will notice that some details are lost in the shadows. Normally I would use Photoshop to manually lighten up areas like the inside of the oilspot teabowl. But with HDR I can capture those details using information in the overexposed shot. This technique works even better with very light objects (like porcelain vases) on a dark background or vice versa.
It might seem daunting for the amateur photographer, but HDR only requires an extra press or two of the shutter. Most cameras offer a multiple exposure setting. If you prefer to shoot manual, remember that you only need to adjust the speed, not the aperture. (Adjusting aperture would result in varying depths of field.) Image processing software like Photoshop and Lightroom 6 include HDR functions, all you need to do is select the files and the software does the rest.
The large photo below is an HDR composite of the four smaller images above it. They were combined in Lighroom 6.
HDR can produce some interesting effects, but when photographing artwork I still haven’t come across a situation in which HDR beats a correctly exposed single shot.
You can scroll over the image above to switch between the HDR and single-exposure photos.
It’s surprising to me how often archaeological discoveries seem to be made in Jingdezhen, but then I remember that wherever I walk in this place there are deep layers of shards beneath my feet.
A friend of mine was given samples from a recently found porcelain stone mine dating from the Five Dynasties Period. Apparently the find has not gone unnoticed- professional antique makers have been secretly mining the site. Luckily we have the chance to acquire some of this porcelain stone.
I’m often dealing with unfamiliar, traditional materials of which chemical analyses are lacking or unreliable. In these cases, I usually create a series of line blends to get a basic idea of what I’m working with. From those first tests, one can further refine glazes using more line blends and triaxials.
For this porcelain stone I created the following initial tests:
- Pure porcelain stone, crushed, milled and sieved.
- Porcelain body using porcelain stone and kaolin at 15-45%.
- Lime-fluxed celadon glazes:
- Porcelain stone and 10-20% Er Hui (Glaze Ash)
- Porcelain stone and 10-20% Wollastonite
- Porcelain stone and 10-20% Whiting
Idealized “traditional” recipes are also based on two-component mixtures. For glazes, porcelain stone was mixed with a flux like glaze ash. For porcelain bodies, porcelain stone was simply mixed with a proportion of kaolin.
Usually a single line blend of either Whiting or Wollastonite could tell you a lot about a porcelain stone. However, porcelain stone mixed with Glaze Ash or Whiting often results in fuming/carbon trapping, so I wanted to test each flux separately. I usually also create Dolomite or Talc tests.
I also prepared two sets of test tiles for cone 10 and 12 firings.
Stones of all types can be used in glazes. Joseph Grebanier’s Chinese Stoneware Glazes lists many recipes that use locally sourced granite. And Brian Sutherland’s Glazes from Natural Sources contains a wealth of information on the subject.