Jim Bozeman on tue 27 jul 99
After the last couple of threads about lustres I dug up some notes that I
had collected some years ago. Please note that I have not tested these
lustres and also no temperature or cone temp was given. OK here goes:
Lustres need reduction, so don't fire in an electric kiln. Lustres should be
mixed with a clay medium. Kaolin mixed with ochrous clay works best. (40%
metal compound to 60% carrier (clay)). Consistency should be like cream. Mix
solution with vinegar instead of water. A few drops of gum arabic will make
the brush flow more easily. It also coats and makes handling of the pot more
easily. (#) Use of bismuth creates an "active" flux and it (lustre) can be
overfired easily. The firing margin of error is small.
Recipies w/flux; active Golden
Red
copper carb: 32
silver nitrate:2
bismuth carb:1 (#) see above
red ochre:65
Recipes w/o flux; passive
Deep Iridescent Red
silver sulphide:6 copper
sulphide:22 red ochre:42
china clay:30
Silver to Bluish Silver
silver chloride:12
tin oxide:10
red ochre:39
china clay:39
Strong
Red
copper sulphide:20
tin oxide:24
red ochre:56
Orange Gold to Red
copper sulphide:27
silver sulphide: 7
red ochre:60
Reduction
should begin at red heat and should go between 5 minutes to an hour. Or you
can reduce the kiln while it is heating up. Both ways work. OK, there you
have it. If anyone does test these would you please post the results.
Thanks, Jim in GA
_______________________________________________________________
Get Free Email and Do More On The Web. Visit http://www.msn.com
Musa Engelbrecht on thu 29 jul 99
Jim, the recipes that you posted would be typical 'clay-paste' lustres.
Briefly, they would be used in the following way:
The 'paste' would be applied to an opaque earthenware already fired glaze,
maturing between 950 C & 1110 C (1742F & 2030F).
(Certain ingredients are vital in the glaze for the lustre paste to react,
e.g. tin and a small amount of lead.) In other words a typical traditional
Majolica glaze.
Ball mill the paste for between 2-4 hours, although I have used pastes
'unmilled' with success. You can also calcine the dry ingredients to 700 C
(1292 F) and ballmill with vinegar. The calcine temp. is not fixed, and you
will get different results using different temperatures.
Paint, sponge and generally use any decorating technique (sgraffito works
well) to apply the paste to the fired piece. Dry thoroughly.
Refire from 600 C (1112 F) to 700 C (1292 F) at which point soak, and then
start to reduce. When cool, rub the clay off and if the gods doth smile
upon you, under the dried clay appears lustres to blow your head off !!!
If you refire the glaze too high the paste will fuse with the glaze at
which point you end up with a horrible dry surface and no lustre. Too low,
and the glaze particles were not excited enough by the heat to combine with
the active ingredients in the paste. Remember, the paste is merely a
carrier for the lustre forming parts. You will also notice that all the
pastes will have an iron content, another vital ingredient in the reaction
process.
Also, your majolica glaze can be decorated in all the usual ways before
using the paste. Oxides used for decoration works better than glaze stains,
with the added attraction of the possibility of the paste reacting with the
oxide in the glaze in a unique way.
You can use an electric kiln, as the reduction is slight, as long as you
have a fully oxidised firing in between. Using wood is the safest reduction
material.
REMEMBER: You are using poisonous materials, and silver compounds will burn
the skin and at very least stain it, that will take at least 10 days to
disappear (I have had the dubious experience) So wear surgical gloves!
EXPERIMENT ! EXPERIMENT ! and remember to write *everything* down....
Anyone interested in (majolica) base glazes and further (tested) clay-paste
recipes, I will be happy to post them.
Greetings,
Musa
The alchemist :-)
Co.Clare,
Ireland.
-----Original Message-----
From: Jim Bozeman [SMTP:idigclay@hotmail.com]
Sent: Tuesday, July 27, 1999 10:45 PM
To: CLAYART@LSV.UKY.EDU
Subject: Lustre Notes
----------------------------Original message----------------------------
After the last couple of threads about lustres I dug up some notes that I
had collected some years ago. Please note that I have not tested these
lustres and also no temperature or cone temp was given. OK here goes:
Lustres need reduction, so don't fire in an electric kiln. Lustres should
be
mixed with a clay medium. Kaolin mixed with ochrous clay works best. (40%
metal compound to 60% carrier (clay)). Consistency should be like cream.
Mix
solution with vinegar instead of water. A few drops of gum arabic will make
the brush flow more easily. It also coats and makes handling of the pot
more
easily. (#) Use of bismuth creates an "active" flux and it (lustre) can be
overfired easily. The firing margin of error is small.
Recipies w/flux; active
Golden
Red
copper carb: 32
silver nitrate:2
bismuth carb:1 (#) see above
red ochre:65
Recipes w/o flux; passive
Deep Iridescent Red
silver sulphide:6 copper
sulphide:22 red ochre:42
china clay:30
Silver to Bluish Silver
silver chloride:12
tin oxide:10
red ochre:39
china clay:39
Strong
Red
copper sulphide:20
tin oxide:24
red ochre:56
Orange Gold to Red
copper sulphide:27
silver sulphide: 7
red ochre:60
Reduction
should begin at red heat and should go between 5 minutes to an hour. Or you
can reduce the kiln while it is heating up. Both ways work. OK, there you
have it. If anyone does test these would you please post the results.
Thanks, Jim in GA
_______________________________________________________________
Get Free Email and Do More On The Web. Visit http://www.msn.com
Musa Engelbrecht on thu 29 jul 99
I just noticed that I made a very definitive statement about using an
'opaque' glaze as a base. You can use a transparent glaze as well on a
white body with underglazes. Stain the transparent glaze with oxides (pale)
then clay-paste lustre on top. I have used cobalt sulphate... works well...
looks good!!
Greetings,
Musa
-----Original Message-----
From: Jim Bozeman [SMTP:idigclay@hotmail.com]
Sent: Tuesday, July 27, 1999 10:45 PM
To: CLAYART@LSV.UKY.EDU
Subject: Lustre Notes
----------------------------Original message----------------------------
After the last couple of threads about lustres I dug up some notes that I
had collected some years ago. Please note that I have not tested these
lustres and also no temperature or cone temp was given. OK here goes:
Lustres need reduction, so don't fire in an electric kiln. Lustres should
be
mixed with a clay medium. Kaolin mixed with ochrous clay works best. (40%
metal compound to 60% carrier (clay)). Consistency should be like cream.
Mix
solution with vinegar instead of water. A few drops of gum arabic will make
the brush flow more easily. It also coats and makes handling of the pot
more
easily. (#) Use of bismuth creates an "active" flux and it (lustre) can be
overfired easily. The firing margin of error is small.
Recipies w/flux; active
Golden
Red
copper carb: 32
silver nitrate:2
bismuth carb:1 (#) see above
red ochre:65
Recipes w/o flux; passive
Deep Iridescent Red
silver sulphide:6 copper
sulphide:22 red ochre:42
china clay:30
Silver to Bluish Silver
silver chloride:12
tin oxide:10
red ochre:39
china clay:39
Strong
Red
copper sulphide:20
tin oxide:24
red ochre:56
Orange Gold to Red
copper sulphide:27
silver sulphide: 7
red ochre:60
Reduction
should begin at red heat and should go between 5 minutes to an hour. Or you
can reduce the kiln while it is heating up. Both ways work. OK, there you
have it. If anyone does test these would you please post the results.
Thanks, Jim in GA
_______________________________________________________________
Get Free Email and Do More On The Web. Visit http://www.msn.com
| |
|
