S Kellam on sat 1 jan 05
I have two questions for all of you experts.
1. Why did my glaze separate in a few small spots on my bisqueware? So, only in one spot on two different pieces, there seems to be a hole in the glaze where the bisque is exposed. Is this because there was a bubble in the glaze that I didn't notice or could it be because the underglaze wasn't completely dry in that little spot? I am hoping to figure out why it happened as to not repeat it again.
And 2. Can I do anything to fix it? Can I reapply some glaze to that one spot (a touch-up so to speak) and refire it or will that not do to the trick or make it worse?
Any advice would be greatly appreciated.
Thank You,
Sherri Kellam
angel_prints@sbcglobal.net
Mark Tigges on sat 1 jan 05
On Sat, Jan 01, 2005 at 12:39:39PM -0800, S Kellam wrote:
> I have two questions for all of you experts.
Sorry but compared to others I'm no expert, you are though welcome to my
experience.
> 1. Why did my glaze separate in a few small spots on my bisqueware?
> So, only in one spot on two different pieces, there seems to be a
> hole in the glaze where the bisque is exposed. Is this because
> there was a bubble in the glaze that I didn't notice or could it be
> because the underglaze wasn't completely dry in that little spot? I
> am hoping to figure out why it happened as to not repeat it again.
When it happens to me it's almost always a result of a fingerprint
which lifted the glaze, and me being too lazy to fix it.
> And 2. Can I do anything to fix it? Can I reapply some glaze to
> that one spot (a touch-up so to speak) and refire it or will that
> not do to the trick or make it worse?
Yes. I do it on occasion for a miriad of reasons. Most often it's
because the piece didn't turn out so nice, and I try (usually in vain)
to make it nice. Fixing bare spots is easier though, and works for me
almost every time to a satisfactory level. You will still notice the
difference, for me usually you will see it since around the bare spot
the glaze is thicker, and so there are subtle differences. This is not
unattractive unless I wanted a really uniformly glazed piece.
Best regards,
Mark.
Ron Roy on sun 2 jan 05
HI Sherri,
Sounds like a pin hole to me - they are not from glazing - but from a
bubble that has not healed over or from a crawl that has not healed over.
I would think refiring would probably fix it.
Perhaps a short soak at the end of your glaze firing will do the trick -
start the soak just as your cone starts to drop and shut off when the cone
has fallen the correct distance.
The glaze could be adjusted for less viscosity as well - easy to do. Send
me the recipe - I might be able to make a few minor changes to help prevent
the problem.
Firing some glazes while they are wet will result in this type of problems
by the way.
Make sure you bisque firing is slow enough to burn out all the impurities
in the clay - I say about 10 hours - and with a spy open to make sure there
is enough oxygen for combustion.
RR
>1. Why did my glaze separate in a few small spots on my bisqueware? So,
>only in one spot on two different pieces, there seems to be a hole in the
>glaze where the bisque is exposed. Is this because there was a bubble in
>the glaze that I didn't notice or could it be because the underglaze
>wasn't completely dry in that little spot? I am hoping to figure out why
>it happened as to not repeat it again.
>
>And 2. Can I do anything to fix it? Can I reapply some glaze to that one
>spot (a touch-up so to speak) and refire it or will that not do to the
>trick or make it worse?
>
>Any advice would be greatly appreciated.
>
>Thank You,
>Sherri Kellam
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Christy Pines on sun 2 jan 05
My question is about the spy hole open for combustion. Does this hold for
electric kilns with kiln vents on during bisque fire? I guess it makes sense
to me. The spyhole lets in new oxygen while the kiln vent takes out the
"old". Yes?
christy in connecticut, had my first ever sale and was VERY pleased with the
results. Looks like I'm becoming a potter!
cpines at ix.netcom.com
From: "Ron Roy"
> Make sure you bisque firing is slow enough to burn out all the impurities
> in the clay - I say about 10 hours - and with a spy open to make sure
there
> is enough oxygen for combustion.
| |
|
