Simona Drentea on wed 21 apr 04
Hello All,
I hope I haven't used up my alottment of questions this month, b/c I have one
that keeps bugging me. I've only fired about 10-15 raku loads, so my
experience is limited. I have seen & purchased over the years many raku pieces that
include both nice white crackle & deep colorful copper matte on the same
piece.
I've only started playing w/white crackle, but when I've tried to accomplish
this, my copper mattes cool & get very dowdy looking. Of course this makes
sense to me, since I know you're supposed to cool the white crackle quite a bit
& I'm sure the copper mattes are getting too cool. What am I missing in how
to accomplish this? Actually, it seems I'm missing everything :-) I don't
understand how I can cool the crackle, yet keep the coppers warm? I know it can
be done, but I'm really not sure what to try next. Any thoughts would be
appreciated!
Thanks in advance,
Simona in unseasonably cold Colorado
p.s. I reduce in newspaper & my pieces tend to be small flat pieces, in case
that matters.
May Luk on thu 22 apr 04
Hi Simona:
I only did Raku twice, but I fired with people who know what they are doing,
well, so it seems.
We get crackles by spraying water [with spray bottle] to the piece after it
comes out of the kiln and before it goes into the sawdust reduction bin.
It's a 2 person operation.
I'm not sure how the americans do it. I have a piece with white crackle
glaze and copper glaze. The copper glaze is shiny though, so I can't tell
you much about that part. Our glazes are old recipes that use lead
bisilicate. This is the only time I used lead fritted glaze in school. But
they come out fat and lovely.
Regards
May
London, UK
P.S. Ababi taught me to raku porcelain paper clay, it worked very well.
Donald Goldsobel on thu 22 apr 04
At the Cahuenga Potter's Studio, the boss man Harry Berman, fast dunks the
pieces in water before post firing reduction begins. It producesgreat
crackles with adequate smoke.
Good luck
Donald
(Do you need a more elaborate signature Mr. Mayor?)
----- Original Message -----
From: "May Luk"
To:
Sent: Thursday, April 22, 2004 2:54 AM
Subject: white crackle/copper matte on same piece
> Hi Simona:
>
> I only did Raku twice, but I fired with people who know what they are
doing,
> well, so it seems.
>
> We get crackles by spraying water [with spray bottle] to the piece after
it
> comes out of the kiln and before it goes into the sawdust reduction bin.
> It's a 2 person operation.
>
> I'm not sure how the americans do it. I have a piece with white crackle
> glaze and copper glaze. The copper glaze is shiny though, so I can't tell
> you much about that part. Our glazes are old recipes that use lead
> bisilicate. This is the only time I used lead fritted glaze in school. But
> they come out fat and lovely.
>
> Regards
> May
> London, UK
>
> P.S. Ababi taught me to raku porcelain paper clay, it worked very well.
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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melpots@pclink.com.
>
sdr on thu 22 apr 04
........I know you're supposed to cool the white crackle quite a bit
> & I'm sure the copper mattes are getting too cool. What am I missing in
how
> to accomplish this? .....don't
> understand how I can cool the crackle, yet keep the coppers warm....>>>>
It is NOT necessary to "cool" white crackle raku. If you are firing it in
combination with copper matt, make the schedule fit the copper matt,
because it is most affected by cooling/oxygen. The crackle in a white
crackle
glaze is mostly affected by the thickness of the glaze and the curve of the
piece being fired. In general, the thicker the glaze, the bigger the
crackle.
The greater the curve, the bigger the crackle. Thin glaze usually equals
a very fine crackle pattern, without any of the large thick lines that
can be achieved with a thicker glaze. You can test this easily on any
piece you fire, by layering the glaze as thick-thicker-thickest, and
observing
the pattern of crackle. The crackling of a raku glaze occurs because
the glaze and clay shrink at different rates. This occurs no matter the
rate of cooling, and I have never seen any difference in the finished
piece that depends upon "cooling" the glaze before putting it in the
trash can, or whatever method is used. Experiment a bit, and see
for yourself.
regards
Dannon Rhudy
Snail Scott on fri 23 apr 04
At 11:47 PM 4/21/04 EDT, you wrote:
>...I don't
>understand how I can cool the crackle, yet keep the coppers warm?
It's not so much that the whites have to be
cool, as that they have to be shocked a bit.
If you cool it suddenly with a spray of water,
you can get the crackle while it's still fairly
hot, and the coppers generally look OK.
-Snail Scott
still in Reno, NV USA
Graham & Rose Mercer on sun 25 apr 04
Simona, another option is to reduce the piece as per your normal copper matt
schedule. The gloss will still crackle, but may not craze in time to pick up
the reduction smoking effect, however if you wipe the glaze over with a
stain or some ink the crackle will stain wonderfully and be quite permanent.
With this method you can also have coloured crackle by using different
stains. Hope that helps.
Cheers from Graham, Melbourne Australia
www.members.optusnet.com.au/~roseandgraham/index.html
Craig Dunn Clark on sun 25 apr 04
The trouble with getting a good crackle and a reduced copper look is
that they are pulling in opposite directions. What has worked for me to a
certain degree is to keep your favorite spray bottle full of water where you
will be able to grab it quickly.
If you are working by yourself this will only work for smallish type
pieces. You will need to practice with the tongs a bit, but you can get
where you can handle the pot in the tongs with one hand and use the spray
bottle with the other. Do it fast. Spritz the areas with the white crackle
just a bit and then into the can. Make sure there is a nice flame, place a
sheet of paper over the top of the pot and seal the can with a nice fitting
lid.
If your cans are old, or new, the seal may not be sufficient so take a
coupla whole damp sheets of news paper and drape them over the open top of
the can before sealing with the lid. Be sure that you see flames hitting the
pot before doing this otherwise you won't get as good a carbon deposition in
the cracks. Try and get the piece into the can and flaming in less than ten
seconds if you want a good copper reduction. The key is directing where the
water is spritzed onto the piece to promote a quick craze and moving as
quikly as you are keeping safety in mind. You don't want to inadverdently
sling molten glaze off the pot if you get overexuberant.
Needless to say, an assistant will help to facilitate things.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "sdr"
To:
Sent: Thursday, April 22, 2004 9:31 PM
Subject: Re: white crackle/copper matte on same piece
> ........I know you're supposed to cool the white crackle quite a bit
> > & I'm sure the copper mattes are getting too cool. What am I missing in
> how
> > to accomplish this? .....don't
> > understand how I can cool the crackle, yet keep the coppers warm....>>>>
>
> It is NOT necessary to "cool" white crackle raku. If you are firing it in
> combination with copper matt, make the schedule fit the copper matt,
> because it is most affected by cooling/oxygen. The crackle in a white
> crackle
> glaze is mostly affected by the thickness of the glaze and the curve of
the
> piece being fired. In general, the thicker the glaze, the bigger the
> crackle.
> The greater the curve, the bigger the crackle. Thin glaze usually equals
> a very fine crackle pattern, without any of the large thick lines that
> can be achieved with a thicker glaze. You can test this easily on any
> piece you fire, by layering the glaze as thick-thicker-thickest, and
> observing
> the pattern of crackle. The crackling of a raku glaze occurs because
> the glaze and clay shrink at different rates. This occurs no matter the
> rate of cooling, and I have never seen any difference in the finished
> piece that depends upon "cooling" the glaze before putting it in the
> trash can, or whatever method is used. Experiment a bit, and see
> for yourself.
>
> regards
>
> Dannon Rhudy
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
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