Hermsen on fri 17 apr 98
O.K., the last two postings got us going on clay and glazes. Now let's use =
the
materials and bring the work to completion through successfully firing.
As mentioned, the White Base Glaze is a good majolica glaze. To do glaze on
glaze painting, first make up a small batch of the Base Glaze leaving out =
the
Zircopax opacifier. This glaze should be mixed to a smooth creamy =
consistency.
To mix an on glaze colour, mix five teaspoons of glaze with one teaspoon of =
dry
Mason Stain and one teaspoon of glycerine to improve flow off the brush. =
This
mixture can be thinned with water as desired. Now this coloured glaze can be
painted directly on top of the base glaze for a true majolica technique.
The White Base Glaze can also be used to make a wide range of beautiful =
solid
colour glazes. This makes for a nice selection of liner glazes. Various =
coloured
glazes can also be sponged over top of a coloured base glaze to give some =
very
rich and vibrant surfaces. Simply add Mason stain to the base glaze in =
various
percentages to achieve the desired colour strength (usually under 10=25). =
The base
glaze can be applied by either dipping or spraying. Do not apply too =
thickly.
The Clear Glaze works well over commercial underglaze colours as well as =
over
coloured slips applied at the leather hard state. It should be applied as =
thinly
as possible, just enough to do the job. The best application is by spraying.=
The
biscuit ware should be clean and dust free or some crawling may occur, the =
same
is true if the glaze is applied too thickly.
Following is an Underglaze Decorating Slip based on a Walter Ostrom recipe:
UNDERGLAZE DECORATING SLIP
Frit 3124 10
OM4 Ball Clay 45
EPK 15
Talc 30
=5F=5F=5F=5F=5F
100
for better brush flow add one teaspoon glycerine
SLIP COLOURANTS
Dark Chrome Green
chrome oxide 2=25
Blue Green
chrome oxide 1=25
cobalt oxide 0.5=25
Cobalt Blue
cobalt oxide 2=25
Navy Blue
cobaly oxide 2=25
rutile 1=25
Copper Green
copper oxide 5=25
Yellow Green
copper oxide 5=25
rutile 2=25
Yellow
rutile 10=25
Black
cobalt oxide 1.5=25
manganese dioxide 3.5=25
iron oxide 2=25
METHOD:
A layer of white (uncoloured) slip may first be applied to the leather hard =
clay
in the area to be decorated. The design can then be roughly sketched in with=
a
brush and watercolour paint as a guide. The design is then painted in with
various coloured slips. Lines may be incised through the slip design with a
sharp ended tool and a soft brush can be used to gently clean the lines.
FIRING
The Redart Clay Body should be biscuit fired to cone 05 (the same as the =
glaze
temperature), this will minimize body outgassing during the glaze firing and
consequently minimize spotting and pinholing. If the style of the work =
permits,
when glazing the pottery, it is a good idea to leave a generous foot of bare
clay, allowing the body to outgass through the clay rather than the glaze =
during
the glaze firing.
The glaze firing schedule can be the same for both the clear glaze and the
coloured glaze (Whew=21 that sure simplifies the firings). The glaze firing =
should
be to cone 05 with a slow top end and a 30 minute soak at the end of the =
firing.
Those who have a computer controlled kiln can do a very slow final ramp from
about 1840 degrees F. to final temp at 30 degrees per hour rise with a 30 =
minute
soak. This will give the most lusciously glossy glaze surface.
I hope that these last three postings have given some of you who may have =
been
contemplating low temperature work a bit of food for thought. As with =
anything
in the world of clay - there is no comprehensive sure fire way of doing =
things -
one must always take what is given and make it your own through trial,
tribulation and testing, testing, testing. The best one can hope for is =
success
through perseverence. Good Luck=21
E-mail: thermsen=40jetstream.net
Web Site: http://www.jetstream.net/users/thermsen
| |
|
