Edouard Bastarache's Lepidolite Glaze Tests

Edouard's Lepidolite test 1051

(French is Edouard's native language, so we will post French first. See below for English)
The recipies are posted at ClayCraft email list.

Introduction Française aux Glaçures Cendrées a la Lépidolite :

Ayant hérité de 10 livres de Lépidolite d'un ami-potier qui fermait son atelier, j'ai décidé d'expérimenter avec ce matériau contenant du lithium qui n'est plus disponible sur le marché.

J'ai déjà discuté des substitutions de ce matériau dans mon livre "Substitutions de Matériaux Céramiques Complexes".

De manière à éviter la production de cloques, j'ai utilisé des quantités médianes de Lépidolite, J'ai aussi utilisé de la Cendre de Bois Dur (Lavée 5 fois et tamisée à 60 mailles) et une fritte de boron pour obtenir une texture de surface que j'appelle "Scintillant".

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English Introduction to Lepidolite Ash Glazes :

Having inherited a 10 pound sample of Lepidolite from a potter friend closing down

his shop, I decided to experiment with this lithium material unavailable anymore on

the market.

I have discussed the substitutions of this material in my book :

"Substitutions for Raw Ceramic Materials

In order to avoid blisters I used a medium amount of Lepidolite. I used Hardwood Ash

(Washed 5 times and 60-mesh sieved) and a boron frit to obtain a surface texture that

I call "Scintillating"

From Glenn C. Nelson’s Ceramics, a potter’s handbook, page 322 of the fifth edition, I have obtained the following chemical analysis of Lepidolite :

SIO2 = 55.00 %

AL2O3 = 25.00 %

FE2O3 = 00.08 %

K2O = 09.00 %

NA2O = 01.00 %

LI2O = 04.00 %

Ignition loss = 0.92 % + 5 % fluorine.

Fluorine is volatile and may cause blisters at high temperatures (Robin Hopper in The Ceramic Spectrum,1984, page 52).

Using the method described in Daniel Rhodes, revised edition of Clay and glazes for the potter at chapter 13 “Glaze calculation using materials containing more than one oxide” under the heading “Feldspar formula” I have defined the following formula for Lepidolite since it is a feldspathoid considered here in its fired or calcined state =

K2O .392 AL2O3 1.0 SIO2 3.743

NA2O .065

LI2O .543 Molecular weight = 384"

Copyright Edouard Bastarache 2005 (all the photos are copyrighted by Edouard. The Blogger setup automaticlly puts my copyright on them, sorry!

"Ils sont fous ces quebecois"
"They are insane these quebekers"
"Están locos estos quebequeses"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
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