Author archive for Derek

  • Glazes

    Cone 6 Oxidation Blue Triaxial Blend

    In Chinese Glazes, we learn from Nigel Woods that the cobalt used for underglaze blue & white underglazes and blue glazes came in a range of chemical compositions and grades of purity.  Thus, there are many shades of blue due to the quality of cobalt-containing stone as well the overlying glaze.

    In the same book, Nigel presents a lovely Chinese blue stoneware glaze which, in addition to cobalt, contains iron and manganese “impurities”.

    In fact I’m personally not fond at all of glazes and underglazes containing only cobalt as a coloring oxide.  Pure cobalt often comes out as a garishly blue color.  In the triaxial blend below, I take a nice clear glaze (Sue’s Clear) with added 1% Cobalt Carbonate.  Then I blend with 1.5% Red Iron Oxide (bottom left) and 1.5% Manganese Dioxide (bottom right).  The resulting colors on the bottom row are much more pleasing to my eye.

    The full image can be viewed here:  http://www.derekau.net/wp-content/uploads/2014/12/BLUE_TRIAX_ALL.jpg

  • Glazes

    Orton Cone 6, R2O 0.2, B2O3 0.18 & B2O3 0.36 Regions

    Having not fired cone 6 since college, I started by first testing a number of clear cone 6 glazes on https://glazy.org

    I also studied up on cone 6 glaze chemistry via Matthew Katz​’s Advancing Glazes course and his papers: Boron in GlazesMid-Temperature Glaze ScienceGlaze Safety/Durable Glazes Presentation.

    Click here for full image of cone 6 clears.

    After selecting the most promising clear glaze (Sue McLeod​’s Clear), I created a biaxial test using similar ingredients with R2O set at 0.2 and B2O3 set at 0.18.

    Having found a very nice looking high Boron clear glaze (WCAC Celadon Clear), I re-made the biaxial with R2O at 0.2 and B2O3 doubled to 0.36.

    Each biaxial resulted in a nice clear, with the higher Boron clear being almost completely transparent and glossy, while the Boron 0.18 clear is translucent and soft.

    Standard Cone 6 Porcelain Body #551

    Link to full-size image here.

    Same chart but with words describing each test glaze:

    Best Clear at B2O3 0.18

    The best clear resulting from the B2O3 0.18 biaxial is here: C6 R2O 0.2 B2O3 0.18 Best Clear

    B2O3 0.36 Biaxial

    In order to test the effect of higher B2O3 levels, I doubled the amount of Boron in the initial biaxial from 0.18 to 0.36 while maintaining the same R2O:RO ratio.  I also made the boundaries of the tests a little higher (see map comparison).  I was surprised to see that the only clear glazes in the 0.36 Boron test appear much farther down (lower in Si & Al) in the chart.  But the “clear” region is still in the same Si:Al Stull region.

    Link to full size image here.

    Best Clear at B2O3 0.36

    The best clear resulting from the B2O3 0.36 biaxial is here: C6 R2O 0.2 B2O3 0.36 Best Clear

    It is similar to WCAC Celadon Clear in it’s glossy, transparent quality.

    From Safety & Durable Glazes Presentation

    From Boron in Glazes

  • Photos

    Smartphone Macro Photography

    I’ve tried a number of smartphone lenses in the article Smartphone Microscopy.

    Today I received my first macro lens for smartphones, the Xenvo iPhone Camera Lens Kit Pro – Macro Lens & Wide Angle Lens with LED Light.

    The lens was a bit expensive ($35), but opening the package I was surprised at the weight and feel of quality materials and real glass.  I’ve only taken a few photos so far but the image quality seems pretty good.

    Xenvo iPhone Camera Lens Kit Pro with LED Light

    Macro Lens & Wide Angle Lens attached to iPhone 7

    Macro Lens attached to iPhone 7

    I’m still not sure how I’ll incorporate macro photos of glazes into my documentation.  So far I’m pretty happy with how the macro photos reveal glaze details not visible in normal photos, but still show the character of the glaze (as opposed to microscopic images).

    Here are some images of Katz-Burke Matte with 5% Rutile 5% Mason 6600.

    Normal photo taken with iPhone 7.

    Macro photo taken with iPhone 7 & Xenvo lens.

    Here are some images of WCAC Clear Celadon:

    Normal photo taken with iPhone 7.

    Macro photo taken with iPhone 7 & Xenvo lens.

    Just to test, here is an example from the Xenvo Wide Angle Lens.  It’s a bit blurry on the edges.

    Original photo from wide angle lens.

    Same photo corrected for lens distortion.

  • Uncategorized

    Clear Cone 6 Oxidation Glazes

    Link to full size cone 6 clear glaze comparison image here.

    Recently I joined a community studio that only fires cone 6 oxidation.  Last time I fired cone 6 I was in college!  So I am learning about cone 6 glazes from various resources:

    Boron in Glazes by Matt Katz

    Mid-Temperature Glaze Science by Matt Katz

    Understanding Cone 6 by Sue McLeod

    These clear oxidation cone 6 glaze recipes all came from Glazy:

    Clear, cone 6 glaze images by Derek

    My personal favorite is Sue McLeod’s clear, followed by the WCAC Celadon Clear.  However, the Celadon Clear is high in boron and may have issues with durability?  The Digitalfire “G” glazes are also quite nice.  Campana clear is very clear on porcelain but peforms badly on the stoneware.

  • Uncategorized

    Clay Akar Yunomi 2018

    Special thanks to those of you who supported ceramic artists in the Clay Akar Yunomi 2018 Show!  I feel very lucky to have my five cups sold.  There are still lots of great cups for sale:  https://www.clayakar.com/pages/yunomi-creators-2018

  • Work

    Jun Variation #2

    Another variation of the Jun glaze, with 2% Bone Ash and 1% Iron oxide.

  • Tests

    Tichane’s Tests

    Some of Robert Tichane’s glaze tests and reproductions of Chinese Glazes donated to the Freer and Sackler Galleries: https://archive.asia.si.edu/collections/edan/default.cfm?searchTerm=tichane&btnG.x=0&btnG.y=0&btnG=Search

    Glaze sample: Jun with copper red; Small bowl with two copper-red spots on outside, two on inside

    Modern reproduction of Yaozhou ware bowl from original mould in Metropolitan Museum of Art

  • Work

    Waxy

  • Work

    Last-minute

  • Craft

    72 Hands

    From the Tiangong Kaiwu (天工開物) encyclopedia compiled by Song Yingxing (宋应星) at the end of the Ming Dynasty comes the oft-cited quote:

    “共计一杯工力,过手七十二,方可成器”

    For the total work required to make a single cup, it must pass through 72 hands, and only then can it become a vessel.

    72 Hands is an effort to document all types of ceramics techniques.  The video style is very simple- a single take of each technique focusing on the artisan’s hands.  Each video is accompanied by an article with a description of the technique and photos.  Videos are shot in high-resolution 4K Ultra-HD resolution which gives a clear view of the technique.

    Support 72 Hands

    To support the continuation of this documentary series, please consider becoming a patron.

  • Work

    From, In, to Jingdezhen

    “From, In, to Jingdezhen; Eight Experiences”, an exhibition organized by Jae Won Lee, brought together a mix of artists who make work in Jingdezhen.

    For this exhibition I refined the porcelain slipware that I began last year, exploring new designs with brushed slip.  I also began a documentary project, 72 Hands (72hands.org), in which I am recording traditional craft techniques in high-definition video.

    Gimhae Clayarch Museum Exhibition Page

  • Work

    Lobed dishes

    A series of lobed dishes inspired by Song dynasty lacquerware.

  • Photos

    Ticking away

  • Techniques

    Plaster Bats for throwing

    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.

     

    Cut a piece of chamois leather slightly larger than the wheelhead.

    Soak leather in water and position on the wheel head.

    Using a rib, scrape out water while the wheel slowly rotates.

    The leather is now completely attached.

    Pour a pool of water or thin slip on the leather

    Dip the plaster bat in water for a few seconds.

    Firmly place bat in the center of the wheel, wiggle until secure.

    When finished throwing, pry off the bat using a flat tool.

  • Techniques

    Working with a mirror

    A potter friend once made fun of me for using a mirror. But no matter how much I improve, I don't think I'll ever stop using a mirror when I throw and trim.

  • Techniques

    Glazing

  • Antiques

    Nothing new under the sun..

    With 10,000 years of history, there’s really never anything new in ceramics, just reinterpretations of the past.  Bowl base fragmentEdo period, Takeo Karatsu type.  Freer & Sackler Galleries.