Saturday, February 6, 2010

This is NOT a Test



Clay is a fickle lover. Popped the top on the SECOND glaze firing… yes, I tried refiring my sgraffito trays/wall tiles thinking I could smooth out the milky-splotchyness of the matt glaze. I had a bit of varied results on the whole load. Couldn’t pinpoint what exactly the issue may be but I was disappointed in most of the pieces. I was hoping for better results considering I used the utmost patience –for me anyways! I THOUGHT, I mixed enough, brushed on enough and let dry enough, even had the kiln controller set to the correct schedule and cone temp of ^05 and even waited beyond the cool down to open the lid. I’m learning (the hard way) that working with clay, you can’t test enough. I’ve admired all the testing Judy Shreve, of Mountain House Studios, has been doing on her Terra Sig journey. Tracey Broome has taught me a lot with her glazing pinhole issues and I admired her for continuing to forge ahead. Reading each post and seeing her photos I could totally identify with the building frustration with each exhaustive round of troubleshooting. It doesn't seem

fair to have a perfectly beautiful piece be ruined at a final stage of firing on a technicality. Clay artists should be able to have a do-over, or some sort of warning flag or digital message that gets sent to us WAY before you open the kiln to disappointment. I know, I know, then we wouldn’t be working in C L A Y –ha!

Above, the Heart tray/tile (used the Amaco Matte glaze) did come out pleasing enough, as well as the small Leaf w/handle tray (used the Coloramics Soft Matte glaze) but the others were not uniform, and on a couple of pieces the black underglaze was altered (the sunflower and Raven Moon pieces being the worse -below). I used two different glazes, the

most successful glaze used was the Coloramics NM-450 Clear Soft Matte, made by Mayco, the other glaze was a Transparent Matte LM-10 by Amaco. The Coloramics only needed two coats and brushed on much nicer than the Amaco. Really none of the pieces using the Amaco Matt Liquid Matte glaze turned out well. A positive was the brightness and true colors (red, yellow, blue and black) of the Duncan E-Z Strokes Underglazes, I love those. Trust me, I’m not totally blaming the material, this seems to be more artist-operator error.

Either the kiln temp/schedule not being quite right (it did fire quick and under 5 hours), glaze too thick, not thick enough or not properly mixed. The good news is I have more sgraffito trays/wall tiles on the drying rack and the Coloramics glaze that I had success with, I have more of. I used up all of the Amaco Mate, so this next batch I’ll use all Coloramics, Clear Soft Matte. I will admit that even with a bit of disappointment, I still don’t think I’m EVER going to be one of those artists that will make tons of tiny test tiles and fire load after load of test firings. Especially since I have a STACK of those smallish tiles, I made over a year ago sitting on the bisque shelf... I’m one of those artists that will just be giving friends and family all my seconds (and thirds) for every conceivable Holiday. Spoiler Alert; Mom, your birthday is this month!!


14 comments:

Gary's third pottery blog said...

email me if you want some cone 6 clear glaze advice including a recipe and what underglazes work with it :)

Linda Starr said...

Oh boy I have found clay and glazes to be very temperamental and fickle, change one thing and it changes so many more things in the end. the heartbreak of allthat work, so disappointing, I so know how you feel.

I'll look at the satin clear I used and see what it is, but it was fired to cone 5/6 which makes a difference. I have used stroke n coat on cone six and cone 10 with good results. But lately I started making my own slip from the same clay and adding mason stains to make the colors to make it more cost efficient with excellent results in all types of clays.

cindy shake said...

These pieces were all using lower temps -bisque fired at ^04 and Fast Glaze fired at ^05. The clay was Tile White ^06-1 and glazes said to fire at ^05 on ^04 fired bisque.

I'm moving onto the ^6 as soon as I test fire some new pod shapes that are currently drying -I need to see if my kilns will successfully fire at ^6 before I get all new clay. Yes, thanks Gary, I will be e-mailing you -all of your glazes are always beautiful! Thank you Linda, it would be good for me to also know a good ^6 clear.

ang said...

ooooh i feel your pain, pouring or dipping is so much easier...get a good clear and stick with it, yu just need to make sure it fits your clay body if you dont want crazing..the clay manufacturers should be able to tell you that, all the best and welcome to the learning curve of ceramics.... :P

Trish said...

Cindy...nice tiles even considering all that you are not happy with..;)
I am sure you have heard of this book: Mastering Cone Six Glazes by Ron Roy and J. Hesselberth.--excellent book.
Have fun. Trish from Alberta

Christine--RHP said...

oh man, Cindy, I feel your pain. I opened a kiln tonight with the freakiest stuff going on...the top shelf bubbled a bit, just enough to ruin several pieces, and the stuff on the other shelves that normally bubble are fine. Loaded evenly, who the heck knows what is going on...
I've been messing with these same glazes for years and they still are unpredictable sometimes.
I've come to the conclusion that certain glazes have a narrow window for success, and the planetary alignment along with application, firing speed, flat or vertical surface, etc can all shrink that window considerably.

Peter said...

Sorry that you are having glaze difficulties, a real shame as you are doing such lovely work.

This will be controversial but, I still think that Lead Bisilicate based glazes for that temperature range are superior to just about anything, they fit well and are nice and clear...., but people seem so scared of them because of the "L" word. Funny thing is that people will use lead crystal wine glasses and think nothing of it!

The borax based glazes are much more difficult to get to fit, and do tend towards making milk rather than crystal clarity (rather like acrylic varnish).

I do wonder if glaze not being properly mixed may have had something to do with the uneven finish, but think that glaze thickness and or the different absorbency of the slip that you had under the glaze is closer to the cause. The detail of the Ravens appears to show that areas where the black slip is thin are more likely to be filled with shiny pools of glaze which matt out where the black slip is thicker.

I am about to embark in some glaze testing of my own for around cone 04, of various lead free fritts, and will certainly post the results, especially if anything worth while comes of it.

All the Best, P :)

ang said...

nice one peter....very clear and concise...i too am a fan of the lead bisilicate commercial glazes, excellent on the earthenware to mid fire range...

Judy Shreve said...

Cindy -- you know I feel your frustration!

The cool thing about low fire is you can keep re-firing. And I have found it's best to do all your underglaze work & fire it first (re-firing and adding color - if needed).

Then add your clear glaze last as a separate final firing.

Judy Shreve said...

Cindy I thought of a few more things -- pinholing can be caused by a couple of different reasons -- bisque speed & temp -- seems you fired hot enough but maybe not slow enough for all the gases/junk to burn out.

Pinholing can also be caused by the glaze not being fired hot enough or held a top temp to allow the bubbling to smooth out.

My suggestions are to bisque on 'slow' -- mine takes about 12 hours. And I fire my underglazes to ^04 & hold for 20 minutes. I bisque & glaze to the same ^04 -- it's easier that way cause I can load the kiln with work at any stage.

Don't give up -- and hey it's all a test tile! lol

jimgottuso said...

clay is a cruel mistress that's for sure. the most encouraging thing i've heard when this has happened to me is... well, you can make more. onward and upward... good luck

Linda Starr said...

I thought the same thing as Judy, bisque temp and fire speed and glaze fast firing may be the problem and was thinking you might try refiring them and see if pinholing goes away. If they aren't functional lead glaze would be good as Peter has said. I recently refired some cone 6 and added more glaze and got better color, I never had much luck with the cone 10 refires except a few pieces. I think I read on Powen's blog he recommended refiring a cone less when refiring.

Patricia Griffin said...

OHHH, how many times have I wanted a "do-over"!!
Just FYI, I've found that firing the underglaze in the bisque firing works the best for me. Sometimes, I'll have a couple of firings before the last glaze firing with my clear.

Kristen said...

Those are super cool!