Monday, 17 December 2012

Not a Very Christian Word was Uttered

Earlier this year we were given the great privilage
of being asked to make a Font bowl for 
  St Mary's Church Barrington.
 Three previous attempts had all ended up in failure. 
I added a deep foot rim to allow for the Lead plug 
in the base of the Font. 
I added a coil and then threw it  
I covered the rest of the bowl to allow it to dry evenly. 
Then I painted it with white slip on the inside
and Blue slip on the outside.
Not my choice, but the Churches.
When dry
Marion got to work on the decoration. 
We took some pictures and Marion set about
drawing the church from a picture.

Very hard work judging by the look on Marion's face . 
 But it was coming on well. 
I added the wording and rim decoration

 It survived the Biscuit firing
so we glazed it and hoped for the best. 
But as you can see it cracked yet again. 
 at this point both Marion & I 
said a few non Christian words.
But I am sure
you will forgive us.
after all it is the season of good will!


Hollis Engley said...

My sympathies, Paul. I have had similar problems with big bowls, and when it's a special order the failure is particularly galling and humiliating. In my case, pieces usually fly across the studio, chased by many of the same un-Christian words you must have used. Wish I had a solution for you.

Ron said...

What a bummer! Hopefully the next one will make it. It's always those darn commissions that give us all the trouble.

Anna M. Branner said...

Oh crap. You are sure to get it right...and then it will be even more valued considering yours and Marion's efforts!

cookingwithgas said...

Buggers and &*^&$$&*$^%#% best of luck with the next one.

Peter said...

Sad and Frustrating for you both. Commissions can be a nightmare, especially at this busy time of year! The cracks look so clean from the photo that they appear to have opened late when the kiln was cooling and the glaze was set. Do you think that the problem may be something to do with cooling too fast or unevenly? All rather strange as I know you must fire many hundreds of pots and bowls with no problems at all.

The following couple of examples are probably not the cause in your situation, but they might help someone reading this...

I remember one potter in my part of the world telling me that they had trouble with tall sculptural work breaking in the electric kiln, and I discovered that they were in the habit of firing with the lower spy hole bung out (someone had told them that it was good to keep the kiln ventilated!). What happened there was that an icy finger of air would run over the piece as it was cooling and cause a temperature gradient through the sculpture that was enough to break it. Smaller work was usually OK.

I myself lost a couple of very tall bowls due to opening the kiln too early and underestimating the amount of stored heat in the kiln shelf that the work was sitting on. There was simply too much temperature difference between the base of the work and the rim, in that case the crack pattern was just a neat, and almost invisible, separation of the bottom of the bowl from the sides.

smartcat said...

This is the kind of thing that leads to head banging in addition to unchristian words! Yes it's big but it doesn't appear to be some crazy out there shape. Could your clay body have anything to do with it? The worst part is not knowing why.

Toes crossed for success in the next one!

smartcat said...
This comment has been removed by the author.
Paul Jessop said...

Thanks for all the comments, I'm going to try a few things differently next time. first I'm going to grog the clay right up i'm thinking about 20%. But the other thing that I hadn't thought about until now is that a few people have suggested that the kiln might be cooling down to quickly, I think you are right Peter, Matt Grimmit also suggested this to me yesterday. and My kiln does cool down very quickly, not a problem with the smaller pots. I can't control the cool down speed on the controller,but I could fill all the gaps with smaller pots to help it retain the heat longer. Thanks for your help it's much appreciated.

Anonymous said...

Your work and your blog are so inspiring, Paul. Marion's drawings are beautiful. Even though it has been upsetting and frustrating seeing the crack, I am sure you will solve the problem and have your beautiful bowl ready soon. Wishing you luck and waiting to see good results.
Shelley from Jerusalem, Israel.

Hannah said...

Buggeration. Buggeration. I know that feeling all too well. Good luck with the next.

Peter said...

Hi Paul,
I was looking at my well thumbed copy of Frank Hamer's Potter's Dictionary of Materials and Techniques yesterday when I was wanting some information about chromium oxide, and I happened to look again at the section he has about the causes of cracking. You probably know his book really well?? There are some interesting diagrams of the different types of cracks that can happen at various times in the potting process, and one type looked similar to the sort that your bowl has. It is a pattern where there is a main crack with subsidiary ones branching from it (he lists this as crack F). Hamer explores the cause of this in some depth, and it is interesting to read.

A quick summary of the cause is that the base of the pot is usually a little too thin in relation to the walls, and when cooling the body contracts a little more than the glaze and ruptures rather than putting the glaze into compression. I am wondering if the added foot ring may have given the effect of a thick wall and thinner bottom? Any glaze pooling or becoming a bit thicker in the bottom of a bowl makes this situation worse.

I guess that fast cooling also would have made this more likely to happen, but I suspect that the primary cause is something like the structural one that Hamer suggests. (I'm interested in Powen Liu's comment about the rim rather than the foot cracking in fast cooling, and that they also mention the thrown foot).

Anyway, sincere sympathy, I hope that the next one you do behaves itself as it is a lovely bowl. P

Paul Jessop said...

Thanks Peter interesting and sounds about right.

Amy said...

thanks for sharing about this. interesting and so helpful to learn! yes, it's the commissions that can be such a headache- as I've learned quickly!

Sometimes sitting doing nothing is the most productive thing you can do.

Apart from a quick clear up in the workshop and the loading of a biscuit firing, to help warm the pottery up tomorrow, today we just gave ou...