Thursday, June 30, 2016

Glazed Work for Rotary Commission (Completed)

Over the weekend and Monday I fired the work for my Rotary Commission. I ended up making and firing 55 pieces, 45 of which are exactly what I wanted them to be.

pieces being unloaded (hot) from the under-fired kiln

The last firing seemed to be taking longer than usual, so I shut it off before the kiln sitter dropped. The kiln sitter is the part in a manually fired kiln that holds a cone. The cone melts at a certain time and temperature (referred to as a cone). When the cone melts, the bar that rests on top of the cone falls, causing the kiln sitter to shut off the kiln.

on the left, my half bent cone; on the right, a correctly bent cone in the kiln sitter

As it turned out, the cone was melting, and I was just impatient when I shut it off early, but most of the glaze melted anyway. Almost all of the commission work was fine. The stuff on the very bottom (not commission work) was under-fired and a few pieces on top also seemed under-fired, including one commission piece.

finished, fired commission pieces


I also had a few pieces that developed cracks in their bases during drying or firing. One cracked during drying, but I forgot and fired it anyway. The others have minor cracks, but I won't send them for the commission.

finished, fired commission pieces with stamps visible


For almost all of the pieces I threw for the commission, 51 pieces, to be exact, I used the same set of stamps to mark the pieces. One stamp says Rotary Yakima, the other has a gear symbol with S/S inside the gear, representing "Service over Self" the Rotary motto. These pieces also have my signature stamp on the other side. 

The stamp set I ended up using for most of the commission.

All three stamps were pressed into the wet clay and later inlaid with blue underglaze to highlight the text and image.

the individual letter stamps and the button stamp


Early on in the project, however, I tried a few other approaches to the stamps. For two pieces, I used the S/S gear stamp and individual letter stamps to write "Yakima Rotary". These are legible and clear, but take up a huge amount amount of space and were time consuming to stamp. Another approach I also scrapped because it was too big: I added a button of clay with the S/S gear stamped into it.

 on the left, the impression of the incised stamp; on the right, the stamp made from the incised stamp

I also fired a piece stamped with one of the very first versions of the Rotary stamp. In fact, this early stamp had lines incised into the Sculpey clay. The stamp I ended up using was one that I made by pressing Sculpey into the first stamp, thus creating the look of incised lines in the clay once the piece is stamped. I fired the test piece so I could see how it looked with underglaze. It looks worse than the new stamp.

most of the finished work


Thursday, June 23, 2016

Glazing for the Rotary Commission

This week I've been working on my commission for the Rotary Club. I threw and trimmed the pieces last week, fired and washed the pieces over the weekend and have been under glazing and glazing them this week. I also fired some sample pieces this week to be sure the glazes were behaving like I expected.
bisque fired pieces drying after their rinse
I had to wash all the fired pieces because I had sanded them while they were dry, before firing. I don't usually sand my work but these pieces had some rough edges as a result of the slashing marks I added while they were wet. If a piece is dusty, glaze may not adhere correctly, so I took the time to wash each piece and rinse off any dust or residue from sanding. 

underglaze applied roughly
For rinsing the pieces, I had a handy bucket of water in the studio leftover from emptying the malfunctioning water heater on Sunday. For some reason I have a dishwasher rack in my studio, so I stacked the pieces on it to dry.

lots of underglaze applied to the first kiln load of work
After the pieces dried, I painted the slashed marks with underglaze and wiped away the excess. 

washing off underglaze and the resulting blue water

Most all of my processes this week felt like assembly line processes. I sanded 50-some pieces, then I washed 50-some pieces, then I painted underglaze on 50-some pieces, then I washed 50-some pieces again. 
all the pots from all the kilns, underglazes and washed
After washing the surface of the pieces again (which left the underglaze inside the slash marks and the stamps as a highlight), I glazed just a few so that I could test the new glazes. 

the test pieces before firing
I am using four glazes, plus the underglaze. All of my glazes are commercial celadons. I have three different interior and rim colors and all of the pieces get a clear coat on the bottom over the underglaze. I ran a small firing this week to test the colors for this commission and to finish a few unrelated pieces from last summer.

the test pieces after firing
After I checked my results, I started glazing the whole batch. I picked just 10 of each color to begin with and was able to glaze the interior and rims of almost 30 pieces in the not-quite-three hours I had available in the morning. In the afternoon I was able to glaze the exterior bottoms in the not-quite-two hours I had between commitments.

The first 10 pieces glazed with Jade on the rims and interior
I'm firing a second kiln now, but because of the size and setup in my kilns (and the fact that I probably need to buy another shelf), I will have to fire at least three more times to complete the commission. Tomorrow I should be able to finish the glazing for the last 20-ish pieces. It should probably take three hours. 

Sky and Jade rims and interiors
To prepare the clay and throw the 50-some pieces took about 6.25 hours. I only needed to make 47 pieces, but I wanted extras in case of cracks, problems with glaze, or other irregularities. I didn't time the trimming very well, but that probably took 6 hours including the time it took me to prepare the stamps. I also spent maybe an hour sanding the pieces, an hour washing the pieces, and a couple hours for the underglaze process. The glaze application should take roughly 8 hours total. Of course I am also loading and firing kilns throughout this process, but I did some of that in between hauling buckets of water up from the water heater with my family and thus didn't time it. At a very rough guess, I'd say this commission will have taken about 26 total hours, not counting planning, firing time, or clean up (the wheel needs to be cleaned between throwing and trimming, the dirty towels need to be rinsed before going in the wash, the trimming scraps need to be collected, the blue underglaze water needs to be changed for clean, the brushes need to be washed between glazing days, etc). 

All 30 pieces with a wonky panoramic shot
Last week, with some of my other commitments, I figure I spent about 25 hours in the studio. I threw and trimmed for this commission, but I also threw a little for a few other projects and I did some unrelated glazing as well as several rounds of firing and I wrote a blog post. This week I was only about to spend about half that amount of time in the studio, but I worked mostly on this commission.

Friday, June 17, 2016

Rotary Commission


This week, my first summer studio work week, I am mostly working on a commission. I was asked to throw a set of matching cups as gifts that Yakima's Rotary Club can present to speakers at their meetings throughout the year. I am basing the cups on some slashed surface pieces I threw last summer.

the prototype pieces

When I agreed to take on the commission, my daughter and husband asked me how long it would take me to throw the roughly 50 pieces for the commission, so this week I timed part of my process. (I meant to time the whole  process, but I forgot.)

25 lbs of clay in 20 pieces

It took me about 20 minutes to cut and wedge one bag of clay (25 pounds) from which I was able to throw 20-24 pieces. It took me about an hour to throw ten pieces. I was able to prepare my wheel, wedge and throw 20 pieces and clean up the wet stuff on my wheel in 3 hours. Then, after a lunch break that involved some mom-duties related to summer camp transportation, I was able to trim all 20 pieces that afternoon.

the wet forms right after throwing

I didn't time the trimming, initially, because first I needed to make and test some stamps. I made the stamps out of Sculpey polymer clay so that I could bake them in the oven and use them right away. It took me about half an hour to form a variety of stamps, then they took 15 minutes to bake. After they cooled, I tried the stamps in wet clay, made adjustment, and fired a new batch of stamps based on the wet clay results. By the time I was ready to trim, I had completely forgotten about timing my process.

a polymer stamp and the results after trimming

I ended up using three stamps for each piece. One stamp is my regular name stamp. The other two are specific to this commission. One says "Rotary Yakima" the other is a gear with "S/S",  referring to the Rotary motto, "Service over Self". In combination I think they are legible yet subtle.

double stamp close up


Over the next few days, I threw and trimmed almost 75 pounds of clay, which was about 56 pieces. I used some stoneware and some porcelain clay. I was able to wedge and throw faster with the porcelain, I think because it was wetter. The stoneware was leftover from last summer and the porcelain I bought last month. 

I tried to redo the video (without the side of the jar in the way), but someone called halfway through. Also I can't listen to my audiobooks while filming at time-lapse on my phone.


I only lost two pieces so far, but about half of them are still wet, so I may have some cracks show up during drying or firing. One had a small crack on its base and another flew off the wheel while I was trimming. I also have a few that I will pull out of the batch because I was trying different stamps on them. I eventually decided the other stamps were too large and looked awkward on these forms.

some pieces ready to trim (with the prototype)

I had one last step to complete before loading up the kiln to fir this weekend. Once the pieces were dry, I sanded down the surfaces of the slashes I had made on the wheel. When I cut the walls, the edges of the cuts were raised up. These were fairly quick to sand down and I think they'll look nicer with glaze. I'm not generally a big fan of sanding bone dry clay, but I wore a mask and will wipe down the table and vacuum. I will also have to wash all the pieces after firing and before glazing so that the glazes adhere well.

sanding station

Sunday, June 5, 2016

Leaching Test for New Studio Glazes

This quarter began with a great deal of energy in the studio around testing new glazes. Most quarters I have my intermediate class mix and test glazes to give them some experience reading glaze recipes, handling materials, glazing, firing, and analyzing test results. Occasionally I have organized larger groups of students to find new glazes or glaze replacements, or to perform leaching tests.

our glaze test bowls laid out before the leaching test commenced

In 2013 I had a large group of students involved in a leaching test to make sure that all of our studio glazes are food safe. About a year ago, I had two smaller groups of students test and mix replacements for the clear glaze we had been using in the class (it was coming out opaque) and for another class glaze that wasn't giving us the color we wanted. Both of these glazes are now used in the studio in place of the old blue and old clear glazes. As a result of the leaching tests, we have relabeled all of our class glazes and are in the process of phasing out our last remaining decorative glaze that is not food safe but could mistakenly be used on a functional interior.

our leaching test with lemon, detergent and control (nothing)

In March of this year, there was a lot of energy and excitement about testing glazes and replacing some class glazes, especially from my independent students. Early in the quarter, I met with the students to discuss the scope of the project, divide up the work and plan when various stages of the process needed to be done. Most students who volunteered (or, in the case of my intermediate class, were required) to be involved were able to find recipes and mix small batches by the agreed upon date. Most of these were then fired and we planned to meet to discuss the results.

The fourth line of bowls (at top) is in a different clay. Most test bowls are stoneware with the spare in porcelain. The celadon clay bodies are reversed with an inlaid coil of stoneware for two bowls because uniformity is, apparently, too difficult.

For a variety of reasons, several students didn't attend the second meeting. This quarter's independent student cohort has been uncharacteristically incapable of getting along in the studio and some of the drama escaped its bounds that day. I've had patches of disharmony in the studio before, but this year, and this quarter in particular, the situation reached an almost unbearable level. It has since gotten marginally better and we were able to complete the work of the quarter, but I am discontinuing the independent class for a time. Some of the students need to move on and find a new place for their work to continue to grow. Some students simply took advantage of my patience and the studio setup too many times until I finally reached my own breaking point.

washed bowls after the test, can you spot a difference?

Even with the drama of these students this quarter, we were able to successfully complete the planned testing process for five glazes, more or less. All five of the tested glazes passed the leaching test, though one test was a little odd since we appear to have two different colors of one recipe. Next week we will decide whether to incorporate any of the glazes into our studio as new glazes or replacements for existing class glazes. We tested two black glazes, one matte and one gloss. We also tested a celadon, a satin/matte orange glaze and a purple/blue glaze that has been hanging around the studio for some time. We (sort of) performed leaching tests on our new-this-year blue and a Shino that gets used sparingly in the studio.

The two bowls on the end only had one bowl dipped in each glaze so the leaching tests had to be done in stages. The cracked bowl is in celadon as are the others in its line. For some reason one of the bowls is blue, the other is taupe; they are supposed to be the same glaze.

If you like the bowls in this test, some of them will be available for purchase in the clay sale this coming November 2016.

Thursday, May 26, 2016

Raku Firing During Class in the New Building

Today was our second class raku firing in our new building. We have a new counter lift system to lift the top-hat off the kiln base. The kiln base is all new bricks this year, though we haven't yet replaced the insulation in the top hat itself.

Wax on the bottoms of cool pieces loaded into a hot kiln starts to burn before the kiln is relit. (image by Dave R.)

Students in my functional pottery, intermediate and advanced wheel and independent study classes met starting today at 9am for the firing. We set up the kiln top on the new winch lift system and put in some glazed pieces.
A spot next to the top hat on the kiln helps dry a pot that was glazed after the deadline.

Our kiln runs on propane tanks and a Venturi burner. We heat the work up to about 1800 degrees in an hour or so. Then when the glaze is molten, the pots are lifted out of the kiln with tongs and placed in buckets of combustibles.
Hot pots coming out of the kiln look black on the outside because the matte glaze doesn't melt. 

Our new space is fairly small, but well protected from the wind and isolated from the main classroom by two sets of doors that help keep the smoke smell contained. We fired, maybe five or six loads of work today, including a few pieces that were refired after less nice results.

Hot pots put into the buckets instantly ignite the combustible materials inside. Students are ready to add more paper on top for even reduction.

We also had a few students try horse-hair raku, where the horse hair is applied to the unglazed surface of a hot pot. The horse hair burns black lines in place on the pot. I think next time we raku, I will prepare the students a little more clearly on how the horse hair process works before they are staring at a hot pot.

Applying horsehair to a small bowl like this takes precision and planning.

As for the glazed, pieces, after the pieces are placed into the reduction buckets filled with shredded paper or leaves, we place a lid on top and let the pieces cool and smoke. The lack of oxygen and the heavy smoke affects the surface of the glaze and the unglazed surfaces of the pots.

Reduction buckets are left to smoke and cool in between firings.

This time we used maple leaves and shredded paper for most pieces. The largest piece was so hot that we had trouble keeping the flames contained inside our reduction bucket. 

Pulling a fired pot out of a bucket sometimes causes the paper to relight.

The reduction atmosphere inside the kiln and in the reduction bucket gave us some pretty good results with at least one of our matte copper glazes. These glazes can look like they have oil spills or flamelike colors on their surfaces.

Our classroom's "Hawaiian Copper Blue"

The matte copper glazes can also be combined with clear gloss glazes to add some shine to the surface. 
This piece has been fired about four different time with glaze added at least twice.

Students who used wax resist to keep glaze from some surfaces of their pots ended up with deep black areas where the smoke was absorbed into the bare clay. 

The white side is a White Crackle Raku glaze with wax resist dots, the green is our classroom's "Texas Twister" copper glaze.

Our most unusual results came from a fairly thick coat of a glossy copper glaze with maple leaves heavily packed on top. 

This glaze benefited from heavy reduction with leaves. The underside is a brighter blue green color.

Sunday, May 1, 2016

Spring Firing Results, Organizing, and Underglaze Color Reference Tiles

I have now fired thrice in the last six weeks, meaning I've been eking out time in my studio to glaze and weekend time to load and fire. The firings have been fairly dull so far; just some low fire odds and ends that had been waiting since last summer.

This is a staged shot, I forgot to actually snap a picture when I was unloading the kiln.

I have a new small kiln that my parents brought me from a friend in Wisconsin. It doesn't have more than one shelf at the moment, but I was able to balance a large domed piece on stills in place of a shelf and thus fire, essentially, two layers of work. 

This is the real firing, after I pulled out the dome piece.

The dome on stilts fired just fine, but either the entire kiln or just some of the pieces under it wobbled at some point, probably when I was closing the lid, and fell off their stilts and into one another. 

Oh no, those red pieces are stuck together!

One small piece fell of its stilt and just glazed itself to the stilt. After unloading that kiln, I realized that it would be beneficial to reorganize (by which I mean organize for the first time ever) my fairly massive stilt collection. 

And that weird purple thing is also stuck to the stilt.

That I have so many stilts is mostly a function of how I got the kilns and partly a function of another  donation of stilts from a now forgotten source. Some of them are great, some of them are not, but I think I've only ever actually purchased one small container of metal stilts.

So many stilts, now sorted by size and type.

The size of my stilt collection is roughly the size of my underglaze collection. After sorting the stilts (with some help from the kid) last weekend, this weekend we sorted the underglazes. Sorting my underglazes consists, in large part, of consolidating half full and mostly empty 2 oz jars  and rehydrating quite a few of them. I have purchased numerous 2 oz jars over the years as portable sample sets and because some colors don't come (or didn't used to come) in pints. Unfortunately the pints stay liquid much better than the small containers.

Duncan Cover-Coat Underglazes

I have two different brands of underglazes (and a few odds and ends). The Amaco Velvets are my faithful standbys and what I use most of the time, but I have full box of Duncan Cover-Coats, too. The Duncan line has some colors I like and they are generally cheaper, but I've had a few instances of peeling underglaze in the last year and those seem mostly to be the Duncans. The Duncan 2 oz jars are great for pouring out glaze, but terrible for this weekend's consolidation project, as the neck of the bottles narrows, preventing a tool from scooping out the extra stuff. 

    
Amaco Velvets and Liquid Underglazes (sorted into warm and cool boxes).

After consolidation, I took a full inventory of my underglazes (and the extra precaution of labeling the lids or easier identification in boxes) so I can replace those I am missing. A few years ago I made some reference tiles for my underglazes. I painted the number of each glaze (the numbers are short and easy to find when reordering) and lines with three different thicknesses of application onto bisque tiles. I then striped one section of the tile with clear glaze and fired them. These tiles are a handy way to check which glaze I used on a fired piece, since wet and even dry glaze doesn't always look the same before and after firing.

Some of my underglaze reference tiles.

With these tiles, my consolidated and labeled bottles, and my inventory, I was quickly able to determine that I am out of Amaco Velvet underglaze V-372 (Mint Green). I needed to determine this because last year I inexplicably used V-372 it on most of the bottom of a piece, but not all. Then I fired it so that it is permanent and promptly forgot what I had done. Now I have to fix it, but at least now I know what I need.