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slip for naked raku versus how to convert percentages into grams

updated sat 29 mar 08


Wally on fri 28 mar 08

Hello Donna,
Your analysis of the weight calculation is absolutely right.
My basic slip recipe for the slip-and-glaze method of naked raku has
always been published and stated as 50 grams dry clay, 30 grams kaolin
and 20 grams flint, no idea about the origin of the misleading
percentage formula.
At home, clay used is "Terre de la Puissaye", a dark grey cone 10
French stoneware clay from the area of Limoges.
In USA, this clay can be substituted by Highwater Phoenix or Laguna
Buff 52 type WC-851, as used with great results during many workshops.
Silica (flint) equal to Quartz 200 Mesh.
Any kind of EPK for kaolin.
On top of this slip comes a glaze with 35 grams gerstley borate and 65
grams frit 3110, wellknown recipe courtesy of Bill and Kate Jacobson.
I hope this fully answers Deborah's question, and clears up the sky
for others who replied to her message.
More details about the technique can be found on my website.
Best regards,
Wally, Schoten, Belgium

--- In, Donna Kat wrote:
> On Sat, 22 Mar 2008 14:22:04 -0600, Deborah Thuman
> wrote:
> >I'll be doing a naked raku next month. I'm sort of on my own with this
> >because my teacher isn't fond of raku. Then again, I can experiment
> >like crazy because my teacher isn't fond of raku. Anyway, I've been
> >told that I have to use a special slip recipe for naked raku and NOT to
> >buy the commercial slip glaze. I've looked through the naked raku
> >archives, and I found the recipe people suggest. But.... it's in
> >percentages and not in grams. How do I convert this recipe?
> >
> >SLIP (by weight)
> >=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >5 % CLAY : Fat French Stoneware "Limoges" clay
> >2 % QUARTZ (=3D flint =3D siliciumoxide)
> >3 % KAOLIN (EPK)
> >very important : sifting 4-5 times through fine sieve (80 or 100 mesh)
> >consistency : medium to fat milk
> >
> Given that this has to add up to 100% to make any sense then as
stated it
> has to be
> 50% clay (ball clay?)
> 20% Silica
> 30% EPK (kaolin)
> Now you have to decide how much slip you want. If you want 100 grams of
> dry ingredients then you would have
> 50 grams clay
> 20 grams silica
> 30 grams epk
> 1000 grams of dry ingredients would be
> 500 grams clay
> 200 grams silica
> 300 grams epk
> Basically whatever total amount of dry material you want would then be
> multiplied by
> .5 (for clay)
> .2 (for silica)
> .3 (for EPK)
> I hope that is the question you are asking. Donna

Wally on fri 28 mar 08

Hello Barbara,

The best stage is when the glaze has just dried up, lost the wet
sheen, but is still a little bit moist.
As you wrote, it can be usefull to apply a fine mist of water if the
glaze has turned too dry, a simple kitchen-type plant-sprayer will do.
Another parameter is the thickness of the glaze.
A thin glaze (say specific gravity of 1.30 or 1.35) works better than
a thick glaze of 1.40, and usually creates less ridges.
The sharpness of the tool is also very important.
A fine iron needle tool will do, but might leave a scratched line,
especially if you use terrasig.
Best tool I found so far is a simple toothpick, or one of those sharp
long wooden BBQ pins normally used to roast meat on charcoal.
Hope that helps.
Greetings from stormy Flanders,
Wally, Schoten, Belgium
-- In, "F. VanSickle" wrote:
> Hello Wally,
> Can you tell us at what stage of dryness you can draw through the
slip and
> glaze layers?
> I have done this when the slip layer is dry enough to handle but not
so dry
> as to flake off. I sprayed a bit of water on areas that seemed too dry.
> The results were good in terms of creating the black lines I wanted to
> achieve, however, the wooden tool I used left ridges on the clay surface
> which interferes with the smooth surface quality of the work. I'm
guessing I
> used too much pressure, although it did not seem so at the time I
did the
> drawings.
> Any advise would be appreciated,
> Thanks,
> Barbara
> PS. Great web site!