I’ve purchased this kiln nine years ago when I first arrived in Jingdezhen. Known as a 烤花炉, this kiln is normally used for overglaze enamels and decals. I paid about $300 USD for it. Only changed two elements in nine years.
Following images from Bonham’s 2014 auction, The Feng Wen Tang Collection of Early Chinese Ceramics
The best resource I’ve found about color in Chinese glazes is Nigel Wood’s Chinese Glazes. Chapter 8, Iron in Chinese Glazes, covers iron in detail, while celadons are covered throughout the book.
There’s a great range of colour in Chinese celadons. In traditional celadons, color is mostly the result of materials containing naturally-occurring iron being fired in a reduction atmosphere, with the color modified by the balance of other oxides in the glaze as well as the underlying clay body. Relatively small amounts of titania, manganese, copper and even cobalt can affect the color in significant ways. Ancient kilns like Yue, Hutian, Longquan, and Yaozhou became associated with certain colors and qualities of celadon, as the materials used at those kiln sites naturally contained particular blends of oxides. In Jingdezhen, celadon glazes seem to have evolved from fairly simple geographically specific material-based recipes (e.g. 10 parts glaze stone from Yaoli, 1 part glaze ash from Leping) to extremely refined and intentional recipes with similar base glazes that incorporate additional materials for their specific ability to modify color. This lead to glazes named not just for kiln sites but also specific colors and qualities: 天青 （sky blue with a small < .2% addition of cobalt），豆青（”bean” celadon pure green iron celadon），影青（”shadow” lake-green)，粉青，玉青 (jade celadon)，冬青 (winter green)，鸭蛋青 (bright duck-egg green), just to name a few.
But celadons in the Song dynasty were mostly restricted to local materials. Thus if your local clay and glaze stone contained only trace amounts of titania and low amounts of iron (such as in towns near Jingdezhen), then you could produce the famously pure blueish-green qingbai glazes. While if you were in the Northern Yaozhou kilns where materials naturally contained more titania, your celadons would tend towards olive-green. (These are greatly over-simplified and generalized statements. Regarding Yaozhou celadons, in Chinese Glazes, Chapter 6, The Stonewares of North China, Woods also mentions the blueish-grey glazes of Yaozhou, as well as the possible influence of coal firing on the color of Yaozhou celadons.)
For me, part of the beauty of Chinese ceramics is the ability of those ancient potters to reveal the beauty of their local materials, and how the resulting aesthetic of each kiln’s wares was in large part driven by the nature of those materials.
Of course, these days most of us make glazes by blending various “standardized” materials, with color variations resulting from additional coloring oxides.
The following test is a simple biaxial blend showing the influence of iron and titania on the color of a base glaze. I’m now using Pinnell Clear for all of my additive tests as I find it a much better glaze than the traditional Leach 4321. Further tests could be done using small amounts of manganese, copper and cobalt, as well as varying the fluxes and silica:alumina ratio. For this test I substituted Grolleg for New Zealand Halloysite, but I did not adjust the recipe to account for the slightly different chemistry. For this test it is important that the base glaze has as little titania as possible, so it’s best not to use “dirtier” clays. The test tiles are made from Jingdezhen “super-white” porcelain, which serves as a good blank canvas for the glaze colors. These glazes look quite different on dirtier porcelains and stoneware.
One year old!
Exactly one year ago, Glazy registration was opened to the public. Since then, we’ve made a ton of improvements and added many more recipes.
94% of website server fees have been paid with your generous donations. Thanks to all of you who have added recipes, photos, and contributed valuable ideas to Glazy. Special thanks to Pieter Mostert and Matt Katz for all their help.
Notable new additions to Glazy:
Stull SiO2:Al2O3 Charts
Si:Al Charts now include a Stull overlay as well as color-coded R2O:RO Ratios. To learn more about Stull, R2O:RO ratios, and other illuminating aspects of glazes, see Matt Katz’s Introduction to Glazes Online.
Simply click the eyedropper icon or one of the photo swatches to search by color. Keyword search is now greatly improved with natural language text search and the ability to search for numbers.
Material Safety Information
Newly added this month are hazard warnings for each material in the recipe. There is still a lot of work to be done in Glazy to provide accurate, easily understandable safety information for potters.
There are more improvements planned. The most important change in the next few months will be the addition of material lists, including regional and supplier lists. Material lists can be shared between users and rated.
WE NEED YOUR PHOTOS!
Ceramics recipes “do not travel well” and are very sensitive to differences in materials, preparation, application, firing, and cooling. The best way to compare, critique, and refine our recipes is to share photos of our results.
If you have photos you would like to share but find the Glazy interface too complicated, contact us and we will help. If you represent a school or studio with a lot of tests, we can help add the photos and recipes for you.
I’m not sure if double-edged safety razor are still available in the West, but here in Jingdezhen they are an essential trimming tool. These razors are thin, sharp, and most importantly flexible. Great for wheel-trimming details on small forms, or for scraping hand-built objects. The most used brand is Flying Eagle. I get the more expensive stainless steel ones. At 5RMB for a 5-pack, each blade is about 15¢ USD.
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.
Recently I’ve been wondering if there’s a reliable way to test glazes for transparency. A method that would allow one to compare results from different firings and glaze types.
Paint manufacturers have a system for testing paint opacity that uses a black and white card from which a contrast ratio can be calculated. The primary manufacturer is Leneta.
I couldn’t find any parallels in the ceramics industry.
I wanted to try a similar method using porcelain (white) and stain/colored porcelain (black), adjusting the results to account for the fact that our whites and blacks are not pure.
Using my whitest porcelain, I created a colored slip adding 8% of a local black stain. (Ideally one would use a standard mason stain.) Adding Darvan, I made a thin slipcast slab that I then cut into small squares.
Using the same casting porcelain I made a thicker slipcast slab which was then cut into square test tiles. The black stained squares were then applied to each test tile and rubbed flat. Finally, the tiles were bisque fired in the hopes of minimizing contamination of the glaze when dipping.
Two 100 gram batches of glaze were prepared: Pinnell Clear and Pinnell Clear with added 10% Zircopax. Using volumetric blending I created tests in 2% increments. The tiles were dipped in the test glazes. Ideally, steps would be taken to ensure even thicknesses of glaze.
The fired tests display a nice opacity gradation as zircopax is added to the glaze.
Unsure of the best way to measure transparency (or opacity) using these test tiles, I tried the simplest approach I could think of. Adjusting the image to greyscale, I averaged the colors of the white test tiles as well as each black-stained square. Below are the Brightness levels measured in Photoshop using the HSB scale. If these tests were going to be made consistent across firings, I suppose one could normalize the photos based on the color of the unfired white porcelain body.
For the opacifying power of Zircopax relative to this specific test, I created an opacity scale in Photoshop using the 0% glaze as a baseline and then matched the tests to this scale. According to the scale, a 4% addition of Zircopax opacifies the glaze by 30%, while a 10% addition of Zircopax opacifies the glaze by 70%. I’m probably vastly over-simplifying things. For instance, I didn’t take into account the fact that the entire test whitens as Zircopax is added. Also, there will probably be few times in ceramics where there is a neat linear relationship, for instance adding 14% Zircopax to the glaze won’t necessarily get me to 100% opacity.
Below is a closeup of the black squares. If I had made these tiles more consistently, with a crisp, straight border between the black and white porcelain, it might also be possible to compare diffusion.
Single photo from iPhone with Eyeskey lens. More details here.
Images generously made available by the British Museum. I have cropped and adjusted levels of the original scans. These are full-sized images, right-click to save.
Two beautiful books of modern Japanese flower arrangement by Kawase Toshiro:
From Creations in Clay, a book of essays and photographs of Brother Thomas Bezanson’s work:
For many years of my work as a potter I was concerned with learning the skills and technologies proper to the potter’s art. I was focused on looking back to accomplishments of the past; I was open to those men and women who shaped the tradition of ceramic art. They were my teachers, by necessity of my ignorance.
Then at some point in a time out of time they left me standing, so to speak, in a dark forest where their ability to guide me came to an end; there was no longer a path of the past to follow. There were no paths at all, except the one I was called to make for myself if I did not want to be just another derivative, condemned to repeat the past, or bootleg from the present.
At this juncture I gradually became aware that my new teacher and best guide was my own work itself. It led me into myself, into my own inner experience.
The Boston Museum of Fine Arts has a small but wonderful collection of Brother Thomas Bezanson’s work. Below are some images from their website.
Having purchased a scanner for digitizing my family’s old photos, I had the brilliant idea to also scan glaze test tiles. I thought I was a genius until Matthew Katz mentioned that he had been scanning tiles for the past ten years.
Matthew noted that CCD scanners have a greater depth of field, which is great for three-dimensional objects like test tiles. Because of his recommendation I purchased the Canon 9000F Mark II.
I’m not a scanner expert and have never calibrated a scanner before. I already have an X-Rite ColorChecker Classic for photography, and this color card can be used with X-Rite’s i1Profiler (i1Publish) software to create a scanner profile. Unfortunately, the software license seems to be very expensive.
I tried Argyll CMS (http://www.argyllcms.com/) but results using the generated ICC profile were worse than the default output.
Here’s a scan of some test tiles. I had to adjust the Exposure in Photoshop by about +1 stop. Notice the reflections on some test tiles that were not flat.
Enable large image scans on Canon 9000F Mark II
The Canon software is really frustrating- by default it wouldn’t let me scan a file greater than a set limit (10208 x 14032 pixels, or larger than 100MB). I finally found a solution hidden away in the software settings.
Comparison with DSLR
I have a relatively old and cheap Canon EOS Rebel T2i with a 18MP sensor. In comparison with the Canon 9000F scans, the photos from my camera are smaller. However, they seem to contain just as much if not more detail and better colors. If needed I can adjust lighting conditions and camera settings to reduce reflections and adjust exposure. On the other hand, the scan had some reflections that I could not eliminate.
It also takes less time for me to take photos than scan at 2400dpi.
Below are comparisons of the scan and the photos. In particular, the dark glazes came out very poorly on the scanner.
In conclusion, while the Canon 9000F is great for scanning old photos and documents, I still haven’t found a way to scan glaze tiles that beats results from my old DSLR.
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.
Eyeskey 12x Micro Lens
It was only after using the Supereyes lens that I realized it’s horrible design (does not fit on camera lens, slides off the camera lens, plastic cover easily scratched, etc.) that I bought another cheap microscope lens, the Eyeskey 12x Micro Lens (also about $7USD).
The Eyeskey model is designed much better. An adapter slides perfectly over the phone and the lens is screwed into the adapter. The plastic tube that is visible using the Supereyes lens is not a problem here. The magnification is also greater than the Supereyes lens.
(Unfortunately I could not find this model for sale in the West. However, I think the 15x Micro Phone Lens might be even better.)
Comparison of Supereyes and Eyeskey Lenses
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).
I tried the iPhone’s panorama feature but it did not work. The iPhone panorama gets confused. However, you can take multiple photos (moving the camera slightly each shot) and then stitch the photos together using software. Adobe Lightroom (Photo Merge->Panorama) and Photoshop (Automate->Photomerge) have this feature , however it takes a lot of time and seems limited to 100 or so photos. I tried a free program called AutoStitch that worked pretty well.
These are some of my great-aunt’s photos of Yangchow camp.
She notes the duration of internment as starting on 13 March 1943 and lasting until 6 October 1945. She was housed in Yangchow Camp “C”.
An interesting history of the camp can be found on Frank Waller’s website at http://www.haikufrank.co.uk/memories_of_yangchow.html
Some of these photos and more can be found on the Australian War Memorial website.
If you have information regarding these photos or would like high-resolution versions, please contact me.