jeudi 14 novembre 2013

Les pieds sont tournassés et des recettes d'engobe / Feet trimmed and slip recipes

La porcelaine est difficile à tourner, bien sur j'en avais entendu parler et je m'étais bien garder jusqu'ici de m'y frotter. Un petit pain que Kai m'avait donné attendait tranquillement dans un coin de l'atelier.

Et puis j'ai eu besoin d'engobe de porcelaine, et je me suis dit que c'était là l'occasion d'essayer. J'ai passé un temps infini à tournasser ces pieds. J'ai vraiment hâte de voir à quel point mes pièces seront déformées ou non. C'est sur, la tasse ansée est déjà déformée.

J'ai décidé de peindre un décor bleu, mais contrairement à mes pièces en grès engobées de porcelaine et décorées sur cru, je vais dégourdir ces tasses d'abord.

Porcelain is difficult to throw, of course I was aware about that, until today I kept myself away from this deal, a piece of porcelain that Kai gave me was waiting in a corner of the studio.
And once I needed porcelain slip, I thought it was 'the moment' to begin with. I spent an infinite time to trim these feet. I cannot wait to know how distorted these cups will be or not. Sure, the handled cup is distorted.
I have decided to paint a blue decoration onto the cups, well rather than decorate on raw as I use to do with my slipped stoneware pots, I will bisque them first.

Recettes d'engobe bleu japonais : Ai (Indigo)

Pour voir des pièces décorées à l'engobe bleu, vous pouvez vous reporter à ce billet, le plus lu du blog, ainsi qu'à la page pièces récentes. Je viens de relire 'Inside japanese ceramics' de Richard L. Wilson et je pense que la recette que j'utilise, celle de Yo Thom est directement inspirée de ce livre, page 114. La recette de Yo Thom vient du livre de John Mathieson : 'Techniques using slips', page 107, 'Ai' (bleu japonais)
La voici :

- China clay (j'utilise du kaolin) 20
- Oxyde de cobalt.....................20
- Dioxyde de manganese.........10
- Oxyde de nickel.....................10
- Oxyde de fer rouge.................5

Dans la mesure ou j'utilise un émail très different du sien, cela donne un rendu très différent de ses propres pièces, qui sont délicieuses.

For blue slip recipes, you can refer to this post, the most widely read blog. You can go to the the page 'Lats works'. I just read 'Inside japanese ceramics' by Richard L. Wilson and I think the recipe I used : Yo Thom's recipe, is directly inspired by the book, page 114. Yo Thom recipe comes from the book of John Mathieson: 'Techniques using slips', page 107, 'Ai' (Japanese blue)
Here it is:

- China clay (I use kaolin) ....20
- Cobalt Oxide ..................... 20
- Manganese dioxide ........... 10
- Nickel oxide ...................... 10
- Red Iron Oxide ................... 5

Insofar as I use a very different glaze of her, it gives a very different rendering of her own pots, which are delicious.

4 commentaires:

Peter a dit…

Bonjour Armelle,

A rainy start to the day here, but there is warmth in the air like summer and all the garden is growing with great enthusiasm!

It is interesting that you are working with porcelain on your side of the world, and I am doing the same over here! I have bisque fired my first kiln load of porcelain mugs, cups and bowls, and all are looking good so far. Like you I have been interested to know if the handles will distort the cups and mugs. I will find out very soon when I glaze fire them! I have had one mug distort badly when drying, but all the rest have been OK. I had some problems with the one that distorted when I was making it on the wheel, and the clay remembered this!

It is strange, but the porcelain that I am using is nicer to throw than my stoneware!! I did not expect this at all, as I have read how difficult porcelain can be, and realise that this must often be the case. I only wish that porcelain was not so expensive here. If I buy 200 kg of porcelain at a time, the price works out at about 20 euro for 10 kg. If I buy smaller quantities I pay more.

I must try out the blue slip recipe that you have posted, it would be interesting to see how it looks with my glazes.

I like the way you have trimmed the feet, it is amazing how important such little things can be!

Kind Thoughts,
P, L, & NS

Armelle Léon a dit…

Bonjour Peter,

Wuthering heights, here, tempest, cold and rainy, well the weather of the season, anyway the grass was growing these last days and needs to be cut off. Happy to know there is warmth in the air in NZ :-)

The porcelain I have got from Kaj is not so easy to throw, I don't know the price, here Ceradel sells differents porcelain. One is nearly 13 euros for 10 kg, when you take 200 kg, and you have to add the shipping 15 euros. For less than 200 kg you pay more, here too. There are more expensive ones.

I don't know if the blue slip is convenient for a bisque. Yesterday I tried it over bisque stoneware cups and I glaze them, so soon I should tell you how it works. Even on raw clay this slip is powdered and no so easy to work with.

Happy you like the feet, I spent a long time to make them. I should have go back to the wheel, but the workshop is so cold, I decided to glaze the pots I had on the shelves. The power cuts rather every day, I am afraid of that for my firing coming soon.

Best wishes to you all

Peter a dit…

Bonsoir Armelle,
Good to read your reply. "Wuthering heights", I like that! I was wondering if the blue slip could be made easier to work with and less powdery if ball clay was substituted for some of the kaolin? On leather hard clay, ball clay could completely replace the kaolin. On dry clay, maybe 50 percent of each?? Another idea would be to add 2 percent bentonite, and possibly reduce the kaolin by 2 percent. Just a thought!

I have been busy glazing today and hope to do a glaze firing on Sunday, or possibly Saturday night. I will be testing a new glaze that I have thought of, so I am impatient to find out if it will work!

It must be very frustrating for you with the frequent power cuts. Our power used to be bad here too, but many power lines were replaced and it is much better now, thank goodness!!!

Kind thoughts from us,


Armelle Léon a dit…

Thank you for your advices Peter, Kaj told me to add silica to the slip to brush onto bisque ware, his blue slip was
ball clay 80,
silica 20
add cobalt carbonate 5.
I remember it was a marine blue under a transparent glaze fired in reduction over stoneware, quite beautiful.
I also use John Britt 'gosu' (japanese Mouse gray should be uses under a shino glaze and fired in reduction)
'Gosu' 2 in The complete guide to high-fire glazes by Jonh Britt
manganese dioxide 10
iron oxide 5
cobalt oxide 20
redart clay 15
kaolin 20
talc 15
tin oxide 15
I used this one and it is blue with my glaze and blur.
I am trying a new glaze too, ha ha !!!
Best wishes for your firing