search  current discussion  categories  glazes - cone 4-7

## oil spot glaze recipe cone 6 question

### Fred Parker on thu 24 sep 09

Did I read somewhere that cone 6 oil spot is not possible for some techni=
=3D
cal
reason? Never seem to see it...

Fred Parker

### John Britt on thu 24 sep 09

Fred,

Yes.=3D20=3D20

You can get small oil spots but since iron begins to thermally reduce at =
=3D
2250 F you don't get much,

John Britt

### Dave Finkelnburg on thu 24 sep 09

Fred,=3D0A=3DA0=3DA0=3DA0 My understanding of this is iron oxide decomposes=
"therma=3D
lly" at ~cone 9.=3DA0 That is, heating breaks the iron oxide into pure iron=
a=3D
nd oxygen.=3DA0 The oxygen bubbles=3DA0out through the glaze and forms the =
oil =3D
0 Wh=3D
at little I know about oilspots I learned from reading his articles and the=
=3D
n confirmed this by testing=3DA0some oilspot=3DA0recipes and firing them to=
dif=3D
ferent maturities.=3DA0=3D0A=3DA0=3DA0=3DA0=3DA0=3DA0=3DA0=3DA0 All the bes=
t,=3D0A=3DA0=3DA0=3DA0=3DA0=3D
=3DA0=3DA0=3DA0=3DA0=3DA0=3DA0=3DA0=3DA0=3DA0 Dave Finkelnburg=3DA0=3D0A=3D=
0A______________________=3D
__________=3D0A=3D0AFrom: Fred Parker =3D0ASent: Thursd=
ay, Se=3D
ptember 24, 2009 5:58:21 AM=3D0ADid I read somewhere that cone 6 oil spot i=
s =3D
not possible for some technical=3D0Areason?=3DA0 Never seem to see it...=3D=
0A=3D0A=3D
=3D0A=3D0A

### Lee Love on thu 24 sep 09

You might be able to get some interesting effects at cone six with
slip glazes under ash glazes. The slip glaze bubbles through the
ash glaze. There was an article about 15 years back in CM.

--
Lee Love, Minneapolis
"The tea ceremony bowl is the ceramic equivalent of a sonnet: a
small-scale, seemingly constricted form that challenges the artist to
go beyond mere technical virtuosity and find an approach that both
satisfies and transcends the conventions." -- Rob Sliberman
full essay: http://togeika.multiply.com/journal/item/273/

### ivor & olive lewis on fri 25 sep 09

<technical reason? Never seem to see it...>>

The temperature for the optimum auto-reduction of Red Iron Oxide at
atmospheric pressure is in excess of 1300 deg C (2372 F)

This can be nuisance when it is not intentional and iron oxide is present a=
s
minor impurity. The oxygen released can give rise to pinholing.

Best regards,

Ivor Lewis,
Redhill,
South Australia