search  current discussion  categories  techniques - slips 

what ravenscrag slip is all about.-long

updated tue 3 dec 02


Kat Valenzuela on sun 1 dec 02

There has been some discussion about Ravenscrag Slip. It is similar to
Slip in that it is a glaze "base" (rather than decorative slip) It can be
fired by itself
at cone 10 for a clear base. I recommend to use additional flux for more
surface interest.
At cone 10 an extra 10% whiting does the trick.
A glaze needs three main things, clay, flux, silica. Ravenscrag Slip has
all three things in various amounts. You can use this as a base
to develop your own glazes. I have been working on several different
glazes and will publish them on a web site (which is under construction) I
will not deal with everything about this since it would be quite long, but
if there is something you want to know email me off list. For those that
want the chemical analysis of Ravenscrag visit and
then search for Ravenscrag Slip. But here are a few recipes I have been
working on.

I have a excellent black recipe for cone 10red. I call it Black Kat
Ravenscrag 80
Whiting 10
Dolomite 10

Add: 13 % iron oxide, and 1.25% chrome. Did the vinegar test and it did
there was no
noticeable leaching.

-Used Ravenscrag at 70%, Dolomite at 20%, and 10% whiting. Got a clear
glossy (with some light greenish coloration) with crystals in wood/salt
kiln. looked good, great depth. cone 10
The best part of Ravenscrag slip is that it can be layered.
In fact I get the most interesting effect by layering.

Cone 6 Base Glossy
Ravenscrag Slip 70
Frit 3134 30

Added: 3%cobalt, 3% rutile, 3% titanium. Got a nice variegated medium blue.
-2%copper and 3%titanium. A nice apple green. Did vinegar test, passable
and did hot/cold water test also passable.

Cone 6 Kat's Matte
60 Ravenscrag Slip
20 Frit 3134
10 Dolomite
10 Calcined Alumina
Added: 2% cobalt, 5% Rutile. Turned out matte blue, breaking green where
thinner. At cone 5,6,7 got the same results so it is not temperature
sensitive. (high alumina matte). Other oxides could be used for this.

High Magnesium Matte cone 6
60 Ravenscrag slip
20 Dolomite
20 Cornwall Stone
*this is matte at cone 6, and 5 but at cone 7 it is glossy. It is
temperature sensitive, Also added cobalt to this, got a mossy green at cone
6 (rather than blue) with 5% rutile of course.

Anyway I have more recipes but wont inundate this group with them all. If
you have some recipes that have been working well for you and you would
like me to share them on the web site, e mail me.

Kat in the Hat
Assistant lab technician
Plainsman Clays