Welcome to Creative Arts Workshop Pottery

Iphone users:  click here to view full site.
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Students, come on in !  We have Spring practice times every day now until June 11th; that is, unless CAW closes due to inclement weather…..click to find out here..  
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.Studio Phone: 203-562-4927 …. ext 18
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Spring Practice Hours from Mar 13, 2017
…..Daytime ……Evening
Monday 12:30 – 3:30 pm  
Tuesday 12:00 – 3:00 pm 5:30 – 7:00 pm
Wednesday…….. 12:30 – 3:30 pm 4:00 – 7:00 pm
Thursday 12:00 – 3:00 pm
Friday 9:30 – 12:30 pm..
Saturday 12:00 – 3:00 pm
Sunday 9:30 am – 12:30 pm .
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Meet – a – Potter

We interview a CAW potter every so often, and post it under the Meet A Potter tab so that you can start developing connections, and we can all get to know one another better. Check out our latest interview, with Ulla Kasten, under the tab or click here.

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Song Dynasty Vase Auctioned for $14.7 Million

vaseThe vase shown here, recently auctioned by Sotheby’s, is a part of the official ware made for the imperial court of the Southern Song dynasty (1127-1279) in Hangzhou. (Click to enlarge.) It has a tooled octagonal profile beginning at the foot, rising through the body, and continuing up its long tapering neck, which is divided into three segments. The rim, however, is circular, flattened to the horizontal, and extends outward to the approximate diameter of the neck’s base. Overall height is 8.5 inches. Judging from the color of the unglazed portion of the foot, the clay appears to be a type of stoneware. 

The glaze is an opaque, satiny, blue-green with modest pinholing and relatively dense crazing. Crazing generally develops in the kiln as it cools; however, it can appear, or continue to grow, over extended periods of time. (Craze patterns develop when a glaze shrinks somewhat more than the clay, putting the glass under tension.

In this case, it appears that a single glaze was applied to the piece, resulting in a monochromatic finish, without visible running, slumping, or overlaps.

A Sotheby’s expert describes the octagonal shape as “very architectural”, a design harkening back to early Chinese bronzes, adding that the Southern Song dynasty suffered from a shortage of bronze because most of it had been melted down for use in warfare. In the state rituals of the dynasty, after the court fled south, it was important to reinstate the political legitimacy of the ruler. Given the shortage of bronze, ceramics were used to copy bronze shapes. 

He further explained that there was a revival of neo-Confucianism in the late Northern and Southern Song dynasties. The values of humility were incredibly important, moving away from the ostentatiousness found in most Tang dynasty arts. This might explain the use of a stoneware clay body over porcelain.

Such a vase is “exceedingly rare”, even in the Palace Museums of Taipei and Beijing, according to Sotheby’s. It had been in a private collection in Japan for the past 40 years. Before that, with a collector in London, where it had likely been brought from China about a century ago.

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Kiln/ Firing Safety

Check out a new description of safety features associated with our kilns and firing process by clicking here , or navigate to the page by pulling down the Studio Info tab – scrolling down to Kilns/Firing – and over to the right to Kiln/Firing Safety.

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Pottery Equipment For Sale

One Shimpo Potter’s Wheel,
One Alpine Kick Wheel,
 & One Econo Kiln.

Need the room.
Make a reasonable offer, and come & take them away.

Contact Phil Levine
203-378-7118

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Specific Gravity of a Glaze

Glazes are mixtures of clays, minerals, and water. Their Specific Gravity (SpGr) tells you how much dry material is in the glaze; commonly thought of as how “thick” the glaze is. A value of 1.4 indicates a pretty thin glaze, whereas 1.7 is pretty thick. Terra Sigilatta is very thin, it has an SpGr of about 1.15; while casting slips are thick, measuring out around 1.75.

Checking the SpGr helps avoid over or under thickness while glazing. Over thickness, of course, is one of the big reasons for glaze runs. Under thickness often leads to dark, muddy results. Having the right SpGr is important to getting consistent glaze results.

A good way to measure SpGr

SpGr 3

Figure 1. Set-up and TARE

1) Place a dry, empty 100ml graduated cylinder (located in the Glaze Room upper cabinet) on the studio scale with enough added weight so that the total adds up to about 0.5 pounds. See Figure 1; click to enlarge. The added weight is needed because the minimum weight for scale accuracy is 0.44 lb.

2) Push the TARE button located on the right side of the keypad. The weight displayed will then drop to zero.

3) Carefully pour 100ml of glaze into the cylinder, and place it back on the scale. Wipe off any excess water or glaze; these create sources of error.

SpGr2

Figure 2. Multiplier converts lbs to SpGr.

4) Use the keypad to enter the multiplier 4.54. This converts the glaze weight into grams and divides by 100 in one step. The Specific Gravity (SpGr) then automatically displays to the right as shown in Figure 2. In this case, it’s 1.41.

5) Compare the result in step 4 to the target SpGr written in the Student Glaze Book (Located in the 2nd drawer of the Glaze Room filing cabinet.) Each glaze is listed on a separate page, and cataloged in alphabetical order.

If your glaze is more than 4 or 5 points too thick or thin, discuss how to proceed with your teacher or a studio potter !  Don’t try to adjust the thickness of the glaze yourself.

OLYMPUS DIGITAL CAMERA

Figure 3. Student Glaze Book

In this case, the glaze is Jasper Tan with a target SpGr in the glaze book of 1.42, noted just below the glaze name, so the thickness is near perfect…..just 1 point on the thin side.

At CAW we bisque to cone 06 (1823F), and adjust our glazes to a SpGr usually between 1.4 and 1.6 .

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Dry Mix-to-Water Ratio:

It’s sometimes handy to know the ratio of dry ingredients to water in a glaze. For example, a SpGr of 1.5  does not  actually mean there’s 50 g of dry mineral in each 100 g of water. That mixture would weigh 150 g, but the volume would be larger than 100ml. That’s because the water alone takes up 100ml of space; the dry mix adds more volume.

A good way to find out the amount of dry mix in a glaze.

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Weigh one cup of glaze, and let the water evaporate.

1. Place an empty, dry container large enough to hold one measuring cup of glaze onto the studio scale, weigh it, and push the TARE button.

2. Pour one measuring cup of glaze into the container. The weigh shown will be the weight of 230 milliliters of glaze. Write down the weight.

3. Let the cup fully dry out (takes a few days), then weigh the cup again. That weight is the weight of the dry ingredient alone, while the difference in the two weights is the water weight.

Ballpark numbers for CAW glazes are between 250 to 300 grams of dry mix per measuring cup (230 ml) of glaze. Since there’s four cups in a quart and four quarts to a gallon, you need 4000 to 4500 grams of dry ingredient per gallon of desired glaze. That means there’s 35 to 40 lbs of dry mix in each full bucket of glaze. For the glaze in Figure 3, Jasper Tan , ingredients are calculated in the book for making 1, 2, 3, & 4 gallons of the glaze.

Interesting Note:  The weight of the dry minerals exceeds the weight of the water in a given volume of glaze !

 

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Greek Terracotta at the MFA

Next time you’re up in Boston, think about visiting the newly organized Greek exhibits at the Museum of Fine Arts. There’s over 200 items on display, newly arranged by theme into three galleries: Homer & the Epics; Dionysus & the Symposium; and Theater & Performance – themes representing the heart of Greek culture.

Greek

Calix Krater, Terracotta, Red Figure, c 470 BCE

 The Homer gallery is devoted to works illustrating the Iliad and Odyssey, including an overview of the Trojan War through scenes on six terracotta vases, as well as marble sculptures and clay statuettes. One drinking cup depicts Helen of Sparta preparing to leave Greece with Paris, prince of Troy, ultimately leading to one of the most famous wars in history. Shown here is a classic red-figure vase from the gallery depicting soldiers in battle during the fall of Troy.  

The Dionysus gallery commemorates the god of the grape harvest, and the Athenian tradition of good conversation sparked by good wine. A silver case displays wine-related pieces used in symposiums, as well as a cup sculpted into a donkey’s head c. 480 B.C.

The third gallery highlights Performance. Terra-cotta pieces here illustrate scenes from lost dramas and comedies; only about 30 of which remain from the classical period. One vase shows Achilles striking down the Greek soldier Thersites, likely inspired by a lost Greek play.

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