David Hendley on mon 27 dec 99
Regarding the 'Ceramic Spectrum' system numbering
system for colorants,
I think a system that limits colorants to between
.625% and 10% is entirely too restrictive.
Especially when designing line blends or tri-axial
blends, I think it is useful to use a higher percentage
of colorant than you think you want as the terminal
points. Just to see what's it's like to be oversaturated,
if for no other reason. For colorants such as iron oxide
and rutile this could easily be greater than 10%.
For commercial stains it could be even higher. I
use 15% stain in one of my glazes.
On the other hand, .625% can be entirely too much
of an ingredient for certain desired effects. For example,
I use a celadon-like ash glaze with .1% cobalt
carbonate - one-sixth as much as your 'lower limit'.
In another glaze, I use .17% granular illmenite for a
gold spotted effect - .625% would be tremendously
overpowering.
As for dropping fractions in the base glaze - it all depends
on how much glaze you are making.
If you are making 10 grams of glaze, the fractions
of grams become pretty important!
I usually figure my glazes to the nearest 1/10 of a
gram (one number past the decimal point). I'll
use this number for a 100 gram batch, but for a 1000
gram or larger batch, all the fractions disappear.
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: Ron Roy
To:
Sent: Sunday, December 26, 1999 8:22 PM
Subject: Re: RR's Revision to Pete's Red - hold everything
| ----------------------------Original message----------------------------
| Hi Ingeborg,
|
| I don't think I understand your question - is it about colouring oxides?
| There are general ranges for colouring oxides but very much depends on the
| type of glaze - I say it is OK to use those general limits - but don't be
| bound by them. Just remember - you want to use as little as possible
| because of toxicity and cost. It is always better to alter the base glaze
| to work well with the colours you want.
|
| As for rounding decimals - it depends - some smaller amounts of strong
| oxides can make a difference if you round off to a whole number - like
| cobalt for instance - or in the main body a strong flux like lithium carb
| could be crucial.
|
| We have to understand about the empirical method - it's more about
quantity
| than accuracy. There is room for both systems of course and the best
| results will be gotten using both.
|
| I tend to get carried away when I am trying to duplicate a glaze with
| different materials - I sometimes feel I need to use some decimals - it
| becomes a target game - kinda silly I know but thats the kind guy I am!
|
| I am quite sure you could round off most decimals and you would not be
able
| to see any difference in the great majority of glazes - but every once in
a
| while I would guess you could.
|
| RR
|
| >----------------------------Original message----------------------------
| >I was a little bit befuddled but with the revisions to the revisions
things
| >are clear. I failed to mention in my report that I rubbed cobalt oxide
on
| >the samples in hopes of seeing it drop into the cracks... negative. I
seem
| >to have no ink on hand so used a magic marker and that was negative.
Will
| >do the freeze/thaw test and see what happens. I don't mind doing the
grunt
| >work since you're providing the brain power.
| >
| >I have wanted to ask your opinion about one of your country men and his
| >methods of glaze formulation. In Robin Hopper's "Ceramic Spectrum" he
| >devises a numbering system for colorants 10% being the greatest amount
ever
| >used down to 0.625% being the smallest amount. He drops all fractions in
| >the base glaze. Perhaps you are familiar with his methodology. At any
| >rate, I always alter my glazes in that manner and wonder how you feel
this
| >affects the end product. I was hesitant to change your revisions as I
| >didn't want to add another variable into the equation.
| >
| >Happy Holiday and I think it is time for me to get myself an
| >Egg Nog ---- without the Egg! Just a Nog.
| >
| >Ingeborg
|
Ingeborg Foco on thu 30 dec 99
Hi David,
I have come across many recipes calling for smaller amounts of colorants
than
.625 and I don't really know how he (Robin Hopper) handles that. Unless I
am not reading
the book correctly, .625% is the smallest amount. One thing I do have to
say
about Robin's book is that it really changed my life in the way I performed
tests. Prior to following his guidelines, I did a lot of testing by the
seat of my pants so to speak. Often times the tests were meaningless (at
least after some time lapsed) as I had difficulty deciphering the results.
I started to work my way thru his book and took all of his suggestions to
heart and feel that I learned a lot and I'm definitely doing a better job in
all areas of testing.
Ron pretty much agreed with your theories. So that leaves me to decide on
how to go
about marking my test tiles. Back to writing hieroglyphs that I can't
figure out later!! Stay with this system or come up with some other
organized way.
Ingeborg
----- Original Message -----
From: David Hendley
To:
Sent: Monday, December 27, 1999 4:45 PM
Subject: Re: RR's Revision - coloring oxides, fractions
> ----------------------------Original message----------------------------
> Regarding the 'Ceramic Spectrum' system numbering
> system for colorants,
> I think a system that limits colorants to between
> .625% and 10% is entirely too restrictive.
>
> Especially when designing line blends or tri-axial
> blends, I think it is useful to use a higher percentage
> of colorant than you think you want as the terminal
> points. Just to see what's it's like to be oversaturated,
> if for no other reason. For colorants such as iron oxide
> and rutile this could easily be greater than 10%.
> For commercial stains it could be even higher. I
> use 15% stain in one of my glazes.
>
> On the other hand, .625% can be entirely too much
> of an ingredient for certain desired effects. For example,
> I use a celadon-like ash glaze with .1% cobalt
> carbonate - one-sixth as much as your 'lower limit'.
> In another glaze, I use .17% granular illmenite for a
> gold spotted effect - .625% would be tremendously
> overpowering.
>
> As for dropping fractions in the base glaze - it all depends
> on how much glaze you are making.
> If you are making 10 grams of glaze, the fractions
> of grams become pretty important!
> I usually figure my glazes to the nearest 1/10 of a
> gram (one number past the decimal point). I'll
> use this number for a 100 gram batch, but for a 1000
> gram or larger batch, all the fractions disappear.
>
> --
> David Hendley
> Maydelle, Texas
> hendley@tyler.net
> http://www.farmpots.com/
>
>
>
>
>
> >
> | ----------------------------Original message----------------------------
> | Hi Ingeborg,
> |
> | I don't think I understand your question - is it about colouring oxides?
> | There are general ranges for colouring oxides but very much depends on
the
> | type of glaze - I say it is OK to use those general limits - but don't
be
> | bound by them. Just remember - you want to use as little as possible
> | because of toxicity and cost. It is always better to alter the base
glaze
> | to work well with the colours you want.
> |
> |
| |
|
