Monday, April 29, 2013

Learning by Failing!

I realise that any form of communication, be it conversation, a written report, or biography, gives a filtered view of reality.  A limited picture.  Most people have a public face, a private one, and an internal world that no one gets to see. 

With crystalline glazing there are successes and failures in roughly equal proportions.  I realize when I look back through my blog that I have said very little about the pots that did not work out, yet these pots are a very real fact of life.  This makes my blog rather unbalanced... too much glitter and success, and not enough disappointment and honest toil!  So, to bring things back to a place that is nearer the truth, I have posted a few pots this time that haven't worked.

Recent Pots With Problems!
Here is an example of a glaze with too many crystals.  This pot needed to be fired to a higher maximum temperature, and probably held at that temperature for a few minutes.  The maximum temperature that you fire a crystalline glaze to determines the number of crystals.  Too high, and you might get none at all; too low, and there are too many crystals.  The margin for error is probably + or - 5 degrees Celsius. 

You can correct this problem by firing a pot with the same glaze to a higher temperature, or by adjusting the glaze formulation.  A little less zinc oxide might help here, and/or some more flux.  An addition of one or two percent lithium carbonate could make this glaze mature several degrees lower.  Glaze thickness can also affect crystal growth, and their quantity.  In general, thicker glazes have less crystals, but they grow bigger.  Thin glazes can have numerous small crystals, and can sometimes be unpleasantly "dry" in feel and appearance.

This pot has very uninteresting crystals and surrounding glaze.  I also do not much care for the colour!  The newly fired pot is shown still attached to its sitter and catching saucer.  The sitter is a ring of clay of the same sort that the pot is made of, and it is matched to make a near perfect fit with the bottom of the pot.  The sitter lifts the pot to safety out of the puddle of glaze that collects in the glaze catching bowl as the pot is firing.  Crystalline glazes are extremely fluid at high temperatures, as you can see by the quantity of glaze that is in the catching bowl.  After the firing, the pot must be separated from the sitter.  I carefully work round the join with a hammer and chisel, and mostly have good success!  The sitter is coated with a mixture of alumina and glue before the pot is placed on it, and the alumina acts as a release agent.

Pale, pretty crystals on this pot, overpowered by the dark brown runs from the tenmoko glaze that I used inside the pot and around the rim.  With some colour combinations this can be very successful, but here the brown is too assertive.

The following two pots were in a firing I did whilst trying to do pots for an approaching exhibition deadline.  The pots were very large, and I could just and so get both of them in my electric kiln with no room to spare for anything else.

Due to the large quantity of zinc oxide in crystalline glazes, usually about 25 percent, it makes things easier to calcine the zinc oxide prior to making the glaze.  To calcine zinc oxide, you put it into bowls that have been previously bisque fired, and you heat it up to a red heat in the kiln.  This process removes the chemically bound water that is in the zinc oxide, and it "pre shrinks" it.  Without this treatment, zinc oxide shrinks a great deal in the early part of a firing, and can cause the glaze to crack up like a dry river bed, and parts of it may even fall off the pot.  When I prepared the zinc for this glaze I slightly overheated it.  The result was that it it made the glaze really difficult to sieve.  I sieved for more than two hours, and finally managed to get the glaze to pass through a 60 mesh sieve.  Mostly I use an 80 mesh for my crystalline glazes, and find that is quite adequate.  Foolishly I gave up at 60 mesh, and assumed that the long firing and the fact that zinc oxide can be a strong flux, would be enough to break the zinc down further and make a working glaze. 

A wiser course of action would have been to have calcined more zinc oxide (to a lower temperature), and made the glaze all over again.

The result of my bad decision and poor glaze preparation, was that the glaze formed a fascinating volcanic looking coating, that scarcely moved at all.  You can see in the first pot with this glaze, that it stops half way down the pot. If it had behaved according to plan, the glaze would have run to the foot of the pot in great waterfalls!  The other thing that went wrong was the under glaze that was put on the bottom half of the pot, this should have been a lacy looking chun glaze over a tenmoko. (blue-white over dark brown).

This was the other large pot that was in the same firing.  Most of the lower two thirds were covered with the problem glaze.  The top quarter had a regular crystalline glaze with some copper carbonate in.  Sadly, I did not take the problem glaze right to the foot of this pot, as I assumed it would have found its way there easily by itself.

Parts of this pot are very good indeed.  I actually like the strange colour and texture of the problem glaze, and the way the glaze above it runs over and into it.  I had to supervise this firing for a mammoth 25 and a quarter hours, and had two one hour sleeps, and one 10 minute sleep over that time.

The last 5 hours of the firing I dripped cooking oil into the kiln as the kiln cooled from 850 to 700 Celsius (1562 - 1292 F).  This gave me the spectacular copper red that you see in the top third of the pot.  I have posted about this oil drip reduction process elsewhere.

If the under glaze had worked properly where you see it near the foot of the pot, or if I had glazed all the way to the foot with the problem glaze, I think this would have been one of my best pots ever.

Anyway, these few examples give you a little glimpse of some of the pots that have not quite worked out over the last month or so.

Whilst they can be a huge worry, very frustrating, financially damaging, and enormously disappointing, failed firings and failed pots are in fact to be welcomed, as they can be the best teachers of all!  One very wise potter once said that there should be a failure in every firing, otherwise a potter is not making progress.

My experience of working with crystalline glazes tells me that in most firings there might be one really good pot, a few more that are OK, and about half of the pots that are not OK.  Occasionally the whole kiln load may fail.

If something does not work, ask and answer the question "why" honestly, even if it makes you look or feel silly!  Why is a good friend!

Finding the Good.
After a week or so to think about things, I am actually quite excited about the problem glaze.  I hope I can reproduce it in future.  I like the strange look of it and the texture.  Used on an appropriate form, I think it could be stunningly successful!  One thing to keep in mind about many of the "artistic" glazes that are used on sculpture or decorative pots, is that they were once glaze failures.  Much admired "crackle" glazes may originally have been badly crazed glazes that were hopeless for domestic ware.  The first crystalline glazes were problem glazes.  I suspect that they occurred first when zinc oxide was being experimented with as a lower toxicity substitute for lead oxide in middle range glazes.

I think that the best way to cope with failure is to cultivate an enquiring mind!


Coming Exhibitions

"Clay Works"
11- 26 May, Aigantighe Art Gallery, Timaru (opening function 10th May).  This is the annual exhibition of South Canterbury Pottery Group. I was asked to be a guest potter at this exhibition and selector and Judge.  Dunedin Ceramicist, John Paxie is the other guest potter.

"Bellamys at Five".
Laura and I will both be taking part in an unusual exhibition that will be held later in the year, from 2 - 22 September.  It is an exhibition where poetry, painting, printmaking, and ceramics are all brought together in one place.  There is a web site associated with the exhibition, and artists and writers that are taking part are being steadily added to the site.

Here is a link to the site.  I sent some biographical material in recently, and Laura's will follow soon.  Bellamys at Five.


gz said...

good to see those that didn't work - and to know why

raindrop said...

Thank you Peter! It is so easy to see a glaze as 'wrong' when it turns out different to what we expeceted and planned isn't it? Recently I inadvertently used a smidgeon of Chrome while firing many pieces of tin glazed ware with the result that my white backgrounds turned pink. I was devastated but a friend thinks they are unusually beautiful.I appreciate your sharing these glazes which behaved in a different way.

Tracey Broome said...

While looking at your beautiful success is always nice, I learned much more today with your failures! I see calcined in a lot of glaze recipes, even calcined chemicals when I was a studio assistant, but I never bothered to find out why it was done, now I know! I learn way more from failure than from success unfortunately :-)

Peter said...

Hello Gwynneth,
Good to hear from you. I see that you are safely back in the UK again after your adventures on this side of the world. Kind Thoughts from us here, P

Hello Jill (raindrop),
Chrome/tin pinks can be "devasting" when they appear in the wrong places. It might be worth keeping a note of what glaze turned pink so readily, as it could be a useful addition to the palette at some point in the future. Some deliberate chrome/tin recipes that I have tried actually don't always work well! From memory, it is glazes that have a goodly supply of calcium that work best for chrome/tin pinks.

Hi Tracey,
I know you have had more than your fair share of "ups and downs" in life lately, and it is good to hear from you. Kind Thoughts from us. xx

Calcining glaze materials can definitely be helpful, particularly china clay or ball clay if a lot of it is used in a glaze recipe. If I was doing a glaze that called for 25 or 30 percent clay, and it was being applied to a biqued pot, I would use about 20 percent calcined clay and 5 to 10 percent regular clay. This goes a long way to making sure that the glaze fits the pot without too much shrinkage whilst the glaze is drying, and through the early part of the firing.

The first crystalline glazes that I ever did, I just used regular zinc oxide, and found that the glaze was almost impossible to apply by brushing or pouring. When I tried brushing, more glaze seemed to come off the pot, than go on it... it was FRUSTRATING! Building it up in thin layers by spraying was the only thing that worked there. Calcining the zinc means I can pour, dip, or brush crystalline glaze.

Angie said...

What happens to your mistakes you keep them as lessons ....or do you smash them up ....some broken bits could be used for mosaics ...I can imagine Laura being good at that ....pot stands to pictures ...another item for fairs.

Thanks for the concern over my tank flood. Thankgoodness nothing below the dripping water got damaged ....a little worried about the ceiling ...and as you said our weather does not help drying ....the loft floor is a bit soggy too. Thank goodness Vicki remebered the plumbing insurance I have ....never before used... they came out and sorted it cost was a tiny ballocck that had broken....Grrrrr.

Peter said...

Hello Angie,

Glad that you were insured for the flood. I wonder if you could borrow a dehumidifier to help the place dry out... (if only you lived closer we could lend you one!!)

Anyway, some of my potting mistakes do get smashed up and added to a growing shard pile. I wonder if it will be discovered in 10000 years time, and archaeologists will judge the state of our current civilization by the quality of my broken pottery??!

I do try refiring some pots, this is a lottery really, but they have been known to come right the second time around, so it is definitely worth trying.

Best Wishes to you, P xx

Armelle Léon Bitterolf said...

Very interesting post Petter, we really have a lot to learn when losing pots, it's really difficult, sometime I don't know why, maybe when the glaze sets a long time in the bucket, some ingredients can change.
Here it's different, the temperature for the calcination of zinc seems to be very important.
I like the pale blue one I don't think that the rim is too dark, it's not a chemical failure, it's your jugement, there !!!

Peter said...

Bonjour Armelle,
le soleil brille! Well, it is here as I write! I think that some glazes do not store well, although others last indefinitely. I read of a potter who had his glazes freeze in winter, and they were quite different when he next used them.

I wondered if someone would like the one with the dark rim, as it does look quite nice in the photograph! It is difficult to know what is nice, nasty, good or bad in one's own work. Sometimes I hide pots away for a few months, and it is easier to make a decision about them when I see them again!

Anonymous said...

Interesting. To my untrained, non-potters eye, the "failures" look good and have certain appeal. I like some of them. I guess that shows how much I know :P

Are you in Timaru from 11th - 26th May? Maybe I'll get to come down to Tims one day during that time.


Rhonda. said...

Hi Peter, Interesting to see this work . There are some potential there. I do especially love the very tall burgundy glazed pot. If it had gone all the way down, I do believe you would have kept it for yourself. Its interesting about when things go wrong when creating. I find this happens often for me in my re creation of clothing garments. I feel The more mistakes the better I have got over the years. The same goes for stained glass and mosaics. EEK, I can remember awful earlier work.Its exciting when it all comes together.I marvel at what the human brain is capable of doing.Being creative is a way of life.Peter you certainly excel there. Rhonda.

Peter said...

Hello there Sue and Rhonda,
How nice to hear from you both! I'm still trying to sort out when we will be in Timaru, but somewhere in that timezone seems very likely, so it will be good to be able to see you if at all possible.

It is interesting to sort out what has "failed" and what hasn't. It is probably easiest where a pot has cracked, or a handle fallen off! It gets so much more difficult when it comes to aesthetic judgements... and, of course, it is natural for what we like to change as life and experience changes us! I think it is important to have a try at deciding what appeals and what doesn't as... then what we produce better reflects us, and not someone else! It is hard to be objective though, and I know that I do sometimes miss what is good, and other times keep work that later proves embarrassing!

Congratulations Rhonda on mastering the commenting system, lovely to hear from you on the blog, and we do rejoice in your creativity too!

Sue said...

I like the second and third pots...the one with the colour you don't like and the blue with dark rim. I think they have a certain rustic and unusual beauty about them.
I do tend to go for things a bit off the wall and out there though.
Be good to see you in Timaru, if possible.
Hi Rhonda!

Peter said...

Hi Sue,
Good to hear which pots you like. Being "off the wall" has a great deal to recommend it. I have a suspician of walls, as they tend to make silly boundaries and they are certainly uncomfortable to sit upon!! Thanks for the "rustic and unusual beauty" it is quite seriously a boost to the morale. :)

Peter said...

Hi "Nancy",
I removed your comment as I was 90 percent sure that it was spam... If not, please try again, but without a link to a commercial product. P