mudduck on sun 15 nov 09
With the talk of starting copper red reduction at cone 012 when do you =3D
start regular reduction??=3D20
I've been starting my normal body reduction at 1650 F. Is this too =3D
soon??
Do you need to do a body reduction and then a separate glaze reduction??
Gene
mudduck@mudduckpottery.net
www.mudduckpottery.net
Edouard Bastarache on sun 15 nov 09
Hey Mud,
I used to clay reduce at cone 08, reoxidise and put the kiln in light
reduction, increasing with time and temperature.
Twice I have skipped clay reduction recently without noticeable difference
in the end product.
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://edouardbastarache.blogspot.com/
http://www.flickr.com/photos/30058682@N00/
http://albertpaintings.blogspot.com/
http://cerampeintures.blogspot.com/
My Books/Mes Livres
http://substitutions.blogspot.com/
Steve Irvine on sun 15 nov 09
Gene,
I start my reduction at cone 05, which is about 1890 F. Once set, I =3D
leave it until I hit cone 10, and then shut off the burners, close up =3D
the burner ports and damper, and let it cool. I don't do any down firing =
=3D
or special slow cooling procedures. A typical firing to cone 10 is no =3D
more than 8 hours. I get bright copper reds, celedons, cobalt blues etc. =
=3D
with this simple approach.
Steve Irvine
http://www.steveirvine.com
> With the talk of starting copper red reduction at cone 012 when do you =
=3D
start regular reduction??=3D20
>=3D20
> I've been starting my normal body reduction at 1650 F. Is this too =3D
soon??
> Do you need to do a body reduction and then a separate glaze =3D
reduction??
>=3D20
> Gene
claybuds@ATT.NET on mon 16 nov 09
Hi Gene,
If you begin reduction at cone 012 and continue in medium reduction, that =
is all that is necessary until cone 9 for great copper reds. At cone 9, put=
the kiln in complete oxidation by turning the burners down to the point wh=
ere temperature is maintained but not increased. Use the heat work of cone =
9 temperature to allow cone 10 to fall. In my kiln it takes about half an h=
our. Then shut down the firing, clam up the kiln, allowing just a small flo=
w of air, and allow the kiln to cool in complete oxidation. You will get fa=
bulous copper reds.
The oxidizing atmosphere created at the impending demise of cone 9 has no =
effect on the glaze, which is by then sealed. The oxidizing finish to the f=
iring clears all your glaze colors and allows a friendly and somewhat prolo=
nged atmosphere for any pinholes etc. to heal over.
One thing that helps a great deal is what Nils mentioned; try to create a=
s much turbulence as possible when you put the kiln into reduction at 012. =
I fire very slowly to cone 012 in straight oxidation, turning up the kiln o=
nly one water column inch per hour. But when cone 012 has fallen, I go from=
4 water column inches of natural gas pressure to 10 water column inches al=
l at once, and this creates a lot of turbulence between gas and air. This t=
urbulence creates an even reduction throughout the kiln and puts the heat w=
here it should be, inside the kiln.
David Beumee
Porcelain by David Beumee
Lafayette, CO
www.davidbeumee.com
-------------- Original message from mudduck =
: --------------
With the talk of starting copper red reduction at cone 012 when do you star=
t
> regular reduction??
>
> I've been starting my normal body reduction at 1650 F. Is this too soon??
> Do you need to do a body reduction and then a separate glaze reduction??
>
> Gene
> mudduck@mudduckpottery.net
> www.mudduckpottery.net
Eva Gallagher on mon 16 nov 09
Hi - I just found the Pete Pinnel article on reduction. He does say the bes=
t
way to find out when to start - as each glaze may be - different - is to ge=
t
two test tiles for each glaze and then fire one in oxidation to a particula=
r
temp - 012, 06 04 , etc right up to cone 6 or even 10.
Then take the ox fired tile along with the unfired glazed test tile and put
them into your gas kiln. Do this for every glaze you are interested in. If
only the unfired one turns out reduced then you have to start redux below
whatever the ox was fired to.
Hope that makes sense- don't know if I explained that very well.
Eva Gallagher
Deep River, Ontario
http://stevenhilljourneyworkshopjuly2008.blogspot.com/
----- Original Message -----
From:
To:
Sent: Monday, November 16, 2009 11:55 AM
Subject: Re: start reduction
> Hi Gene,
> If you begin reduction at cone 012 and continue in medium reduction, that
> is all that is necessary until cone 9 for great copper reds. At cone 9,
> put the kiln in complete oxidation by turning the burners down to the
> point where temperature is maintained but not increased. Use the heat wor=
k
> of cone 9 temperature to allow cone 10 to fall. In my kiln it takes about
> half an hour. Then shut down the firing, clam up the kiln, allowing just =
a
> small flow of air, and allow the kiln to cool in complete oxidation. You
> will get fabulous copper reds.
> The oxidizing atmosphere created at the impending demise of cone 9 has no
> effect on the glaze, which is by then sealed. The oxidizing finish to the
> firing clears all your glaze colors and allows a friendly and somewhat
> prolonged atmosphere for any pinholes etc. to heal over.
> One thing that helps a great deal is what Nils mentioned; try to create
> as much turbulence as possible when you put the kiln into reduction at
> 012. I fire very slowly to cone 012 in straight oxidation, turning up the
> kiln only one water column inch per hour. But when cone 012 has fallen, I
> go from 4 water column inches of natural gas pressure to 10 water column
> inches all at once, and this creates a lot of turbulence between gas and
> air. This turbulence creates an even reduction throughout the kiln and
> puts the heat where it should be, inside the kiln.
>
> David Beumee
> Porcelain by David Beumee
> Lafayette, CO
> www.davidbeumee.com
>
>
>
>
>
>
>
>
> -------------- Original message from mudduck
> : --------------
>
> With the talk of starting copper red reduction at cone 012 when do you
> start
>> regular reduction??
>>
>> I've been starting my normal body reduction at 1650 F. Is this too soon?=
?
>> Do you need to do a body reduction and then a separate glaze reduction??
>>
>> Gene
>> mudduck@mudduckpottery.net
>> www.mudduckpottery.net
>
>
claybuds@ATT.NET on thu 19 nov 09
Ivor and Dave,
Ivor wrote,
" If, at cone 9, the
> introduction of an Oxygen has no effect on the glaze what do you mean by
> "The oxidizing finish to the firing clears all your glaze colors "
I mean that oxidizing the kiln at or about cone 9 clarifies all glaze color=
=3D
s because blemishes disappear in an oxidizing atmosphere and do not heal ov=
=3D
er if I continue reduction through to the end of the firing. For my kiln, a=
=3D
n excess of gas at 012, from 4 to 10 water column inches all at once, means=
=3D
an excess of gas; reduction atmosphere is created. At or about cone 9, I t=
=3D
urn the gas back to 4 water column inches of gas pressure; an overabundance=
=3D
of oxygen; oxidation atmosphere is created. The idea at cone 9 is to turn =
=3D
down the gas pressure to a point where temperature is maintained but not in=
=3D
creased, thereby allowing a soak in oxidation while heat work drops cone 1=
=3D
0.=3D20
Ivor asked; " Are you
> dealing with the secondary reaction or only describing gas flow in the
> burner ? In other words, how would I ensure a uniform reducing atmosphere
> within my kiln if my secondary air vents are not sealed ?
By the time 012 falls, I have both primary and secondary air ports are wide=
=3D
open, and they stay that way from 012 to cone 10. By increasing the gas pr=
=3D
essure to such an extent all at once, I am creating a short, bushy flame wh=
=3D
ich roars audibly. I want to draw in the maximum amount of air from both pr=
=3D
imary and secondary sources to be mixed with an excess of gas pressure to c=
=3D
reate the maximum amount of carbon monoxide and hydrogen, the real work hor=
=3D
ses of reduction. When secondary air is closed, the flame lengthens and the=
=3D
refore decreases the amount of heat inside the kiln and can cause streaming=
=3D
; poorly mixed air and gas. Pots can come out reduced on one side and oxidi=
=3D
zed on the other. The creation of a short, bushy flame means maximum turbul=
=3D
ence, meaning even reduction throughout and maximum heat exchange and incre=
=3D
ase inside the kiln.
My cycle is 10 hours beginning to end; four hours from start to 012, anothe=
=3D
r 3 hours to cone 5/6, and another 3 hours to cone cone 10. I allow about 3=
=3D
0 hours cooling time.
David=3D20
=3D20
-------------- Original message from ivor & olive lewis =3D
OM.AU>: --------------
> Dear David Beumee,
>=3D20
> I read your post of 16 Nov 2009 and noted a couple of paragraphs that wer=
=3D
e
> interesting.
>=3D20
> The first was ....
>=3D20
> <
> effect on the glaze, which is by then sealed. The oxidizing finish to the
> firing clears all your glaze colors...>>. Today I returned and re-read yo=
=3D
ur
> statement. There seems to be a contradiction. If, at cone 9, the
> introduction of an Oxygen has no effect on the glaze what do you mean by
> "The oxidizing finish to the firing clears all your glaze colors "
>=3D20
> Without clarification , this seems to be a contradiction.
>=3D20
>=3D20
>=3D20
> My second point relates to your early firing. Having read Nils Lou on
> Turbulence I wonder if I understand the cause of this phenomenon. I
> appreciate the result is to get a uniform mixture of gas and air. This ta=
=3D
kes
> place within the bodies of our burners before gas is ignited at the flame
> retention ring. But excess gas, as it is injected into the Kiln cavity, m=
=3D
ust
> be prevented from meeting air from a secondary source to achieve uniform
> reduction, or it will reignite.
>=3D20
>=3D20
>=3D20
> You write "....I go from 4 water column inches of natural gas pressure to=
=3D
10
> water column inches all at once, and this creates a lot of turbulence
> between gas and air. This turbulence creates an even reduction throughout
> the kiln and puts the heat where it should be, inside the kiln....) Are y=
=3D
ou
> dealing with the secondary reaction or only describing gas flow in the
> burner ? In other words, how would I ensure a uniform reducing atmosphere
> within my kiln if my secondary air vents are not sealed ?
>=3D20
>=3D20
>=3D20
> Best regards,
>=3D20
>=3D20
>=3D20
> Ivor Lewis,
> Redhill,
> South Australia
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