Dawnisaacs@AOL.COM on sun 12 may 02
I have some purple powder in my studio. which was given to me by somebody a
long time ago, with the label "dark blue" on it. Can't remember what it is?
Could someone please enlighten me? Would be so grateful to know what it may
be?
Also if I may be so bold as to pose another question -
I bisque fired some terracotta mugs to 1050 andnow want to glaze fire with
transparent glaze but to leave some areas without any glaze at all. Is that
a
bad idea or will it be ok? Thanks for your help. Dawn
Lori Leary on sun 12 may 02
Dawn,
Sounds like you have some Colbalt Carbonate on your hands. Used as a
colorant for colors from light blue to deep blue. Expensive stuff, but a
little bit goes a long way.
Hope this helps.
Lori L.
lleary@epix.net
Mountaintop, PA
> I have some purple powder in my studio. which was given to me by somebody
a
> long time ago, with the label "dark blue" on it. Can't remember what it
is?
> Could someone please enlighten me? Would be so grateful to know what it
may
> be?
> Also if I may be so bold as to pose another question -
>
> I bisque fired some terracotta mugs to 1050 andnow want to glaze fire with
> transparent glaze but to leave some areas without any glaze at all. Is
that a
> bad idea or will it be ok? Thanks for your help. Dawn
>
>
Marianne Lombardo on sun 12 may 02
Dawn;
My Cobalt Carbonate is a lilac purple colour, and cobalt is used to make
blue, so that's my guess. 3% added to a clear base will make a dark blue.
Is terracotta the same as earthenware clay? Low fire - ^06 or ^04? If so,
I think because mugs are washed so much that the clay would be too porous
with a lot of unglazed areas and you may get crazing on the glaze with time.
Marianne
> I have some purple powder in my studio. which was given to me by somebody
a
> long time ago, with the label "dark blue" on it. Can't remember what it
is?
> I bisque fired some terracotta mugs to 1050 andnow want to glaze fire with
> transparent glaze but to leave some areas without any glaze at all. Is
that a
william schran on sun 12 may 02
Dawn - Purple powder may be cobalt carbonate or a stain that may
produce any number of blues to purples. I'd first just mix little
with water and paint over a white or clear glaze on a test piece to
see what the results are.
Terracotta will never be water tight, so for functional forms
probably not a good idea the leave unglazed areas.
Bill
>I have some purple powder in my studio. which was given to me by somebody a
>long time ago, with the label "dark blue" on it. Can't remember what it is?
>Could someone please enlighten me? Would be so grateful to know what it may
>be?
>Also if I may be so bold as to pose another question -
>
>I bisque fired some terracotta mugs to 1050 andnow want to glaze fire with
>transparent glaze but to leave some areas without any glaze at all. Is that
a
>bad idea or will it be ok? Thanks for your help. Dawn
>
>___________________________________________________________________________
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>Send postings to clayart@lsv.ceramics.org
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>melpots@pclink.com.
Ababi on sun 12 may 02
It is either cobalt carbonate or, more likely dark blue cobalt stain,
You have found your gold mine!
Ababi
---------- Original Message ----------
>I have some purple powder in my studio. which was given to me by
>somebody a
>long time ago, with the label "dark blue" on it. Can't remember what it
>is?
>Could someone please enlighten me? Would be so grateful to know what it
>may
>be?
>Also if I may be so bold as to pose another question -
>I bisque fired some terracotta mugs to 1050 andnow want to glaze fire
>with
>transparent glaze but to leave some areas without any glaze at all. Is
>that a
>bad idea or will it be ok? Thanks for your help. Dawn
>________________________________________________________________________
>______
>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.
Tommy Humphries on sun 12 may 02
I must agree with all the rest, if your powder is lavender to a dusky bluish
gray color you have cobalt carbonate...However...
Once I found a bag of powder in some old pottery stuff that had been
sitting in an old storeroom for nearly 30 years. Upon opening it up I found
it contained a dark metrically lustrous extremely fine purple powder. The
bag also contained an old silver plate spoon, which when extracted from the
powder was stained an extremely dark blue...I was puzzled, to say the least,
as this looked like nothing I had ever experienced in clay materials.
I took a level spoon full of this mystery powder and added a few drops of
water and the powder completely and instantly dissolved into an almost
black, deep blue liquid.
INK!!!
Asked a few of the old timers that were still around at the time, and they
recalled a big batch of ink that had been bought for marking stripes on
strawberry jars for the location of the pockets...said that they had been
using food coloring, but the ink was a lot cheaper. Only one problem...the
ink did not completely burn out in the firing and left a dark mark on the
pot, not a good thing.
I tried it out, and sure 'nuff there was that faint blue line on the clay
after firing.
Anyone know what kind of ink this was??
Tommy
PS my fingers attested to the fact that the ink was permanent...after a week
potting I still had blue stained fingers, just from handling the spoon!
Michael Banks on mon 13 may 02
Dark blue stain (cobalt silicate) is a purple powder, Dawn. So, that is
likely it.
But I suggest you add a few percent to a clear glaze on a small tile and do
a test trial.
Michael Banks,
Nelson,
NZ
----- Original Message -----
Dawn Isaacs wrote:
> I have some purple powder in my studio. which was given to me by somebody
a
> long time ago, with the label "dark blue" on it. Can't remember what it
is?
> Could someone please enlighten me? Would be so grateful to know what it
may
> be?
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