Randy McCall on wed 29 sep 10
I have a glaze and want to either lighten or darken the color=3D2C should I=
d=3D
ecrease all the coloring oxides or increase all the coloring oxides respect=
=3D
ively. Or should I just decrease or increase the red iron oxide in the gla=
=3D
ze. I have increased and decreased iron oxide in another glaze and it basi=
=3D
cally didn't change the color=3D2C but it did affect the brightness of the =
gl=3D
aze.
Randy
=3D
Lynn Goodman Porcelain Pottery on wed 29 sep 10
Randy-- Please post the recipe, firing temp, kiln atmosphere
(oxidation or reduction), and anything else that might affect the
glaze's color. Without that info, anyone replying would just be
guessing.
Thank you--Lynn
On Sep 29, 2010, at 3:16 PM, Randy McCall wrote:
> I have a glaze and want to either lighten or darken the color,
> should I decrease all the coloring oxides or increase all the
> coloring oxides respectively. Or should I just decrease or increase
> the red iron oxide in the glaze. I have increased and decreased
> iron oxide in another glaze and it basically didn't change the
> color, but it did affect the brightness of the glaze.
>
> Randy
>
Lynn Goodman
Fine Porcelain Pottery
Cell 347-526-9805
www.lynngoodmanporcelain.com
Robert Harris on wed 29 sep 10
I would say that it's almost impossible to answer that question based
on the amount of information you've given. It definitely depends on
which colorants you are using. For example if you've got cobalt or
copper in they're your definitely going to want to alter them.
If it were me I would do a bi or triaxial blend with your colourants.
If that is too complicated I would start from scratch with you base
glaze and do the following.
Whenever I've got a new base I want to play with I initially do a
simple line blend with 3 or 4 colourants, say Iron, Cobalt, Copper,
and Chrome or Manganese. If I want a blue I then pick the approximate
shade from my cobalt line blend and do two or three simple line blends
with Iron and with Manganese, depending on if I want a slightly
purpler blue, or a slightly muddier blue. In my experience cobalt on
its own is always a bit stark.
When I wanted a blue-green I did a chrome blend, picked one or two
amounts of chrome that looked "about right" - then did a cobalt line
blend with that glaze.
Hope that makes sense.
Robert
On Wed, Sep 29, 2010 at 3:16 PM, Randy McCall wrote:
> I have a glaze and want to either lighten or darken the color, should I d=
=3D
ecrease all the coloring oxides or increase all the coloring oxides respect=
=3D
ively. =3DA0Or should I just decrease or increase the red iron oxide in the=
g=3D
laze. =3DA0I have increased and decreased iron oxide in another glaze and i=
t =3D
basically didn't change the color, but it did affect the brightness of the =
=3D
glaze.
>
> Randy
>
>
--=3D20
----------------------------------------------------------
Darlene Yarnetsky on thu 30 sep 10
If you have a lot of oxides in the glaze and you increase each of these, yo=
u
will also effect the surface of the glaze - Iron oxide especially can act a=
s
a flux. You run the risk of making the glaze more runny, so if you go that
route, you may need to make changes in the base glaze composition.
If you just want to lighten the hue, add some tin oxide, or other opacifier=
,
zircopax or such. Rutile may lighten some, but may also mute the color a
little bit, and can make a glaze with a lot of other oxides a bit more runn=
y
as well.
To darken the glaze, conversely, the easiest choice would be to remove or
lesson the amounts of any opacifiers. I think small amounts of added cobal=
t
would darken an already dark hue easier than the iron if running is a
concern, but it depends on what you are going for. Keep in mind, if you ar=
e
using this glaze for food ware, to test for durability if using a lot of
oxides.
Hope this is helpful, and happy testing!
Darlene
mudcatpottery.com
May Luk on thu 30 sep 10
Randy;
If you have 2-3 colorants, you can do a triaxial blend
http://www.triaxialblend.com
This site makes it look very complicated, but you get the idea. I
remember the explanation is simpler in Robin Hopper's book.
http://www.amazon.com/Ceramic-Spectrum-Simplified-Approach-Development/dp/0=
=3D
873418212
Another book to look is Micheal Bailey's cone 6 glaze book. There is a
chapter on the red iron glaze and you can see the gradation from his
line blend.
Hope this helps
May
Brooklyn
On Wed, Sep 29, 2010 at 3:16 PM, Randy McCall wrote:
> I have a glaze and want to either lighten or darken the color, should I d=
=3D
ecrease all the coloring oxides or increase all the coloring oxides respect=
=3D
ively. =3DA0Or should I just decrease or increase the red iron oxide in the=
g=3D
laze. =3DA0I have increased and decreased iron oxide in another glaze and i=
t =3D
basically didn't change the color, but it did affect the brightness of the =
=3D
glaze.
>
> Randy
>
>
--=3D20
http://twitter.com/MayLuk
http://www.ceramicsbrooklyn.com/
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