Colorado Art Studio

Returning to my regularly scheduled clay blog after going off topic the other day…

I really want to expand my glaze palette and am searching for some fun translucent candy colored bright eye popping color to highlight the texture on a lot of my new hand built pieces.  I’m testing glazes in oxidation (electric kiln for you non-clay people) at cone 6 (temp 2232 degrees F) on a white stoneware clay body called Ash (available from Mile Hi Ceramics).

The glaze properties I’m looking for include:

• a tight fit (no running off my ware)
• translucency
• vibrant color
• stable - no crazing, pitting, crawling or pinholing
• food safe
• cost effective and reasonably safe raw materials

Colors I’m working on:

• Chartreuse
• Pink
• Orange
• Violet
• Robin’s Egg Blue

I already have a celadon, clear and white glazes in my repertoire.  If you’re a clay person, you probably already know that the colors I’m striving for are hard to get in the properties I’m looking for at higher temperatures outside of maybe commercial glazes (I could very well be off the mark though since I consider myself a novice glaze chemist) .  These colors are widely available in low fired earthenware pottery.  But, once you move into mid-range and high fire, many of these colors burn out mainly the pinks, reds, yellows and oranges.  Or they require a reducing (gas kiln) atmosphere in the case of reds and oranges.

To achieve color in glazes one can use oxides or manufactured stains.  There’s a few stain companies out there such as Mason, Cerdec-Degussa inclusion pigments, and Blue Heron (can’t find company website) - and maybe more that cater to commercial manufacturers of ceramics & pottery.  Oxides include copper carbonate, cobalt carbonate, iron oxides, chromium, manganese to name a few.

So, for this glaze testing cycle, I chose to test pink and chartreuse colored glazes.

Glaze Test Recipes

What you see isn’t always what you get when it comes to glazing!

I did a 6 part color progression test for each of the test glazes (one of the recipes isn’t listed as I added it at the last minute) using Ceramic Spectrum by Robin Hopper, pg. 187 as my guide.

Only 1 of my glaze tests turned out the way I expected!

The others are all duds unless you consider drab olive green pleasing… so back to the drawing board me.  I actually anticipated that 2 of them would fail after further research & AFTER I had already mixed up the test batches, but fully expected Glaze #1, 2 and 3 to turn out.  I also realized last night that I misread the glaze I really wanted to try for glazes #1 and #5 and used a different one than intended - doh.  #2 is pretty - but it’s an ineffective way to get blue when I could simply use cobalt carb.  The chartreuse stain was tested on a semi matte base glaze, which I’m not sure I like.  It’s looks more mustardy yellow than acid yellow-green.  A gloss may be better - so I’m going to keep on testing before trying a new stain.

I thought I had fully accounted for how all the different chemicals & minerals were going to react in the kiln, but I was wrong.  I became painfully aware of the fact after I downloaded 2 different trial glaze calculation programs.  I’m testing Insight (free trial for 2 months) and Glaze Master (also available as a free trial for 2 months).  I really like Insight since it felt pretty intuitive to use - but I really need to read the instruction manuals to really use both of the programs to their full advantage before making a purchasing decision.  There is also a free glaze calculation program called, appropriately, The Glaze Calculator, that I should probably investigate.  Here’s a bigger database with different glaze calculator programs that are available.

Since I’m really looking for stable glazes to use on surfaces that come into contact with food, certain chemicals are off limits and I really need to read up on glaze expansion, alumina/silica ratios and while I’m familiar with limit formulas, it’s only starting to make sense me.  I really wish I had paid more attention in chemistry class.

On one hand, I feel like I’ve got just enough information to be dangerous or simply very frustrated - and liken myself to throwing darts in the dark hoping to open the kiln and find success with any luck.  On the other hand I’ve been doing so much reading regarding glaze chemistry that I realize how much I have to learn.

Meanwhile, a fellow clay person and Etsy Mud Team Member, Eleanor pointed me in another new direction - that of lanthanides or rare earth minerals as colorants for glazes.  She pointed out these 2 articles Rare Earth Colorants by Max Campbell and Chris Keane and Exciting New Transparent Glaze Colors Using Lanthanide Colorants by David Pier.  Although, after a little bit of research, Laguna clay has stopped distributing Praseodymium which creates the greens and yellows due to steep increase in price (so this may be a dead end)- but there’s always Praseodymium yellow Mason Stain #6408 to use as a substitute.

Update: I just found this article by Tony Hanson that includes a recipe as a starting point for making a pink ^6 glaze.  My problem?  In addition to not having zinc in a chrome/tin glaze, there can be no magnesium.  If I had seen this little tid bit before (and it clearly states that in the Mason Color Chart which I neglected to see even though I’ve read the damn thing 100 times) I would have realized that my test recipes above contain Magnesium!  Doh

Back to chemistry class for me!

~Cynthia

This post is overdue by a couple of days, but don’t worry - I am not feeling guilty about it.  On the contrary, I feel pretty proud of myself that I abstained for as long as I did since I’m trying to wean myself off my addiction to the computer.

I’ve traced the paper template for a large mug onto linoleum

I decided to take my paper cup template that Annie shared with us during a workshop I took with her 2 weeks ago and make a custom lino-cut in the shape of the template with very specific imagery.  Before making this, I decided if it works out I’d make some more linoleum blocks to add to my repertoire.  One of the hazards of taking workshops is that my work could end up looking like the presenter’s work and that’s the last thing I want to do.

Freshly cut linoleum

Since the template is basically a cone shape, I have found that the flat rectangular linoleum blocks don’t print the way I want them to since there’s a curvature once the mug is assembled.  I used my poppy linoleum cut as reference for this one.

Freehand drawing in pencil

Traced the drawing in sharpie marker

Many of you thought that the black sharpie drawing was actually underglaze or some other material to transfer the image block to clay, much like a paper print.  At this point, I’m simply using the lino-cuts as texture tools to transfer the imagery to clay.  It sure as heck beats hand-carving each and every piece.  Essentially, the carving is done only 1 time when I make the lino-cut and I’ll be able to use this for years.  The sharpie marker basically firms up and simplifies where I need to cut since many of the pencil marks overlap.

Freshly carved lino-cut

Finished stoneware relief printed poppy mug

Well, it’s almost finished - this one is still green and must survive the bisque and glaze firings.  I’m not in love with the handle template and am trying to figure out how to alter it to suit my tastes.  I’m starting some glaze testing too using mason stains as colorants.  I want a bright sherbet Technicolor palette.  Some where in my blog travels one of you mentioned Colour Lovers - which is this wicked cool web based color and pattern maker.  You can browse the libraries or make your own palettes and patterns.  My daughter and I played around with this site the other day for hours.

I’m not sure whether or not I’ll be able to truly achieve this bright of a glaze palette since glaze chemistry is tricky.  I’m going to start with the use of mason stains and need a couple of good base glaze recipes.  I already have the celadon color so I really only need to work on the other 4.  Yesterday, I spent the day reading up on the use of Mason Stains as colorants in glazes vs. oxides.  From what I’ve read, the reds, pinks and oranges sometimes need a higher calcium based glaze to achieve the color shown and the presence of zinc can change the color.  So, some testing is in order in the next week.  I think I’m going to head over to the Colorado Potter’s Guild studio on Tuesday evening to mix up a few 100 gram batches of 2 different base glazes to start with.  The glazes also need to be transparent to highlight the texture on my new work.

Frog Stoneware Box

On Saturday, afternoon, I finished up the second of 2 boxes I assembled last week.  My relief printing efforts are the result of all the hand painted porcelain boxes I’ve made in the past couple of months.  The boxes are incredibly time intensive and I need to be able to work more efficiently.

Duds

This became apparent when these boxes came out of the kiln either glazed shut or some otherwise damaged.  I was heart broken, but if ceramics teaches anything it’s humility and working out the technical aspects of working with clay.  So, after briefly flirting with getting a 9 to 5 job, wiping away my tears and frustration, I became determined to figure out how I can make better work with minimal losses.  Somehow, the prospect of becoming a claims adjuster trainee for an insurance company just doesn’t sound too fun or glamorous.

Meanwhile, I have been losing tools left and right in the studio.  I know that they can’t just get up and walk out the door and that they’re in there somewhere!  The problem is that my studio hasn’t been properly cleaned in months.  1/4 bags full of different kinds of clay littered the floor, dust was everywhere, clay bits and scraps everywhere, trash, bits of paper, notes etc. were strewn about.  So, I spent yesterday afternoon cleaning my studio top to bottom.  It’s sparkling clean (well as sparkling as a ceramic work area can be) and ready for a new productive making cycle.

Have a great week,

~Cynthia

Last Thursday, I spent most of the day at the church where the guild holds its sales photographing work to use in future show advertisements and on their website. Our sale runs Thursday - Saturday for obvious reasons and the church apparently gives the guild favorable rental terms. It doesn’t hurt that it’s huge and that there are numerous rooms at our disposal. Some might consider it sacrilege, but we did our photographing in a small intimate annex chapel with the set up above - notice the cross behind the photo tent. It worked so well, I think I’m going to abandon photographing outside with my ghetto setup. The room was completely dark except for the lighting on the tent. We were able to get some great shots this way.

Platter by guild member, Kathleen Laurie, photographed in our set up

Meanwhile, during the marathon photo session, a few swear words escaped our lips - and we all laughed nervously while asking for forgiveness.

I’m feeling the urge to do a little glaze testing. Last night, I dusted off my copies of Mastering Cone 6 Glazes by Hesselberth & Roy as well as my copy of The Ceramic Spectrum by Robin Hopper. I’m feeling pretty relaxed now that the sale is over and I really do need to expand my glaze palette.

My in-laws are flying up today for a few days. They didn’t want to miss my daughter’s performance at the Shakespeare Festival on Friday and then we’ll spend Mother’s day together as a family.

Tonight, my husband and I are going on a rare date. We”re going to see Justin Currie, former lead singer of Del Amitri at the Toad Tavern. I’m not normally a live music fan, but this will be in an intimite venue - so I won’t feel so claustrophobic since there shouldn’t be any large crowds to speak of.

Happy Wednesday,

~Cynthia