Terrie Lambert on sat 9 aug 97
Hello, I have been on the list for a short time. I would like to say that it
is very informative.
I am having a problem with a manufactured glaze made by Duncan. It is called
Antique Bronze SY 554. It is a low fire glaze that I have fired successfully
to ^5 in my test kiln. The test kiln is 6" x 4", app. and electric. I am
firing the glaze on both a black and a white porcelain made by laguna. The
pieces are cylinder in shape about 3" long. I dry foot. I fired them
straight up real fast (about 1.5 hours to complete) and they are absolutely
beautiful. A very smooth metallic mirror, sometimes more silver, sometimes
gold. One very heavy coat is all that is needed to acquire this finished
surface.
The problem is that when I fire in my larger kiln's, either the 18" or the
28", the pieces are matt gunmetal. So I re-apply and fire 1 to 3 times to
achieve the same surface, but I can never get the top edge to look like
anything but matt gunmetal. I can take a piece that has fired like this and
not apply anything else to it, put it in my test kiln and it will come out
with a nice black mirror. All edges just fine, minus the metallic finish.
The firing time (straight up) on the 18" is 6 hours, on the 28" 8.5 hours.
Also when this happens there is an underlying white blue beneath the metal
surface when I manage to achieve it. Not so in the test kiln even on
re-fired pieces.
Could I be losing the something to fuming when it takes this long? Any
suggestions would be just great. I am now quite behind on a very large order
for these pieces and more than a little concerned.
Thank You,
Terrie Lambert
Ron Roy on sun 10 aug 97
Hi Terrie,
My guess is - the longer cooling in the bigger kilns is giving the glaze
time to recrystallize. I assume your test kiln cools faster. Most super
cooled liquids (shiny glazes) will recrystallize given enough time - and it
sound like this glaze is loaded with oxide to get that black.
How to cool the bigger kilns faster - open the spy holes for starters - a
vent would be the next step and leave it on during cooling.
>I am having a problem with a manufactured glaze made by Duncan. It is called
>Antique Bronze SY 554. It is a low fire glaze that I have fired successfully
>to ^5 in my test kiln. The test kiln is 6" x 4", app. and electric. I am
>firing the glaze on both a black and a white porcelain made by laguna. The
>pieces are cylinder in shape about 3" long. I dry foot. I fired them
>straight up real fast (about 1.5 hours to complete) and they are absolutely
>beautiful. A very smooth metallic mirror, sometimes more silver, sometimes
>gold. One very heavy coat is all that is needed to acquire this finished
>surface.
>
>The problem is that when I fire in my larger kiln's, either the 18" or the
>28", the pieces are matt gunmetal. So I re-apply and fire 1 to 3 times to
>achieve the same surface, but I can never get the top edge to look like
>anything but matt gunmetal. I can take a piece that has fired like this and
>not apply anything else to it, put it in my test kiln and it will come out
>with a nice black mirror. All edges just fine, minus the metallic finish.
>
>The firing time (straight up) on the 18" is 6 hours, on the 28" 8.5 hours.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/people/ronroy.htm
Huck4u on tue 12 aug 97
Sounds like you are either not firing hot enough or are not venting
properly . Plus firing with other kinds of glazes will effect metallic
glazes easily . Contact your suppler or Ducan .Huck4u@aol.com
Terrie Lambert on wed 13 aug 97
At 11:08 AM 8/10/97 EDT, you wrote:
>----------------------------Original message----------------------------
>Hi Terrie,
>
>My guess is - the longer cooling in the bigger kilns is giving the glaze
>time to recrystallize. I assume your test kiln cools faster. Most super
>cooled liquids (shiny glazes) will recrystallize given enough time - and it
>sound like this glaze is loaded with oxide to get that black.
>
>How to cool the bigger kilns faster - open the spy holes for starters - a
>vent would be the next step and leave it on during cooling.
>
>
Hello Ron,
Thank You!!!!!
This was the problem. I was already leaving the spy holes open, so what I
did was propped the kiln lid (1") 10 minutes after the kiln shut off. Then
as the kiln cooled I would open it more. The cooling time in the little kiln
would be between 1.5 and 2.5 hours, depending on when I opened it to see.
This would usually be when all glow was gone.
I now have very shiny, beautiful pieces.
I thank you again.
Terrie Lambert
| |
|
