Wyndham Dennison on sat 9 aug 08
> Date: Fri, 8 Aug 2008 16:40:05 -0400
> From: Ingeborg Foco
> Subject: Re: ^10 - ^6 shino
>
> The worst part is that when I take a special order in that glaze, */_I have to
> make a bunch more and toss the rest. _/* It is to the point where I am thinking
> of doing away with it completely since it is such a headache for me. You
> can see a teapot on my website which is nice white and orange. I also have
> a platter on the main gallery page (left side top) that is orange and
> white. None of my materials have changed. I have mixed new batches and
> found it made no difference.
To be frustrated with a glaze is understandable but you should never
have to toss the glaze. It does not go bad. It may change % of
ingredients because a soluble ingredient has been used up(Soda Ash).
Most Shino's will become whiter the thicker the glaze. This can be a
benefit if one wants to make a mark or decoration by brushing on more
after dipping. Several things to look at, since soda ash is water
soluble some of this is leaving with the water as well as the glaze so
the 7% may well be half that part way through the bucket of glaze. A 16
oz plastic solo cup will hold about 500g of dry glaze in 16 fluid oz's
of wet glaze. +or- some. Take a 16 oz cup of glaze and divide it into 4-
4oz batches. Each batch will have about 125 grams of ingredients in each
cup. Mark the first as a baseline to tell you what the original glaze
is then add 2% soda ash to cup 2(mark it) then 4% to cup 3 then 6% to
cup 4. Apply to marked test tiles and see what the the results are.
The other possibility is the density has changes because of evaporation.
Check with a hydrometer at the beginning batch and check before each glaze.
I have had shino's dry out in a bucket for six months add water, screen
and ready to go. Timing of the reduction cycle can be a possible prob
but unlikely if the pots look good on early glaze but changes as the
glaze goes down. Since the Spodumne also can be a problem a touch of
lithium might be another addition.
Since there's as many taste in Shino's as there are potters, my
favorite Shino has a small ant of temoku added to make it a bit richer.
Hope this helps Wyndham
Ingeborg Foco on sun 10 aug 08
Hi Wyndham,
Thanks for your suggestions, they are certainly worth trying. However, do
you have any clue as to why a new batch would manifest the same problem as
the old stuff in the bucket which may well have less soda ash than a newly
mixed batch? I am wondering if I am just to close to the situation and
there is something very obvious and correctable that I am missing.
I did not make it clear when I said I have to make a bunch more and toss the
rest. I was referring to say an order of 6 mugs where I have to make a ton
more and hope at least 6 come out. I don't throw the glaze out. I have
though mixed a new batch to see if it reacts differently and unfortunately I
had the same headache, pasty white pots that do not sell even if I mark them
down.
If you can solve this dilemma, I would be happy to send you a pasty white
pot :) I will try a tad of Tenmoku and see what comes of that. Normally, I
sprinkle a little wood ash on top of the shino glaze before it dries.
It adds it a bit of interest.
Ingeborg
> "To be frustrated with a glaze is understandable but you should never
> have to toss the glaze. It does not go bad. It may change % of
> ingredients because a soluble ingredient has been used up(Soda Ash).
> Most Shino's will become whiter the thicker the glaze. This can be a
> benefit if one wants to make a mark or decoration by brushing on more
> after dipping. Several things to look at, since soda ash is water
> soluble some of this is leaving with the water as well as the glaze so
> the 7% may well be half that part way through the bucket of glaze. A 16
> oz plastic solo cup will hold about 500g of dry glaze in 16 fluid oz's
> of wet glaze. +or- some. Take a 16 oz cup of glaze and divide it into 4-
> 4oz batches. Each batch will have about 125 grams of ingredients in each
> cup. Mark the first as a baseline to tell you what the original glaze
> is then add 2% soda ash to cup 2(mark it) then 4% to cup 3 then 6% to
> cup 4. Apply to marked test tiles and see what the the results are.
> The other possibility is the density has changes because of evaporation.
> Check with a hydrometer at the beginning batch and check before each glaze.
> I have had shino's dry out in a bucket for six months add water, screen
> and ready to go. Timing of the reduction cycle can be a possible prob
> but unlikely if the pots look good on early glaze but changes as the
> glaze goes down. Since the Spodumne also can be a problem a touch of
> lithium might be another addition.
> Since there's as many taste in Shino's as there are potters, my
> favorite Shino has a small ant of temoku added to make it a bit richer.
> Hope this helps Wyndham
>
--
Dale Neese on mon 11 aug 08
Ingeborg,
I don't think it's the glaze that is the problem. I use a Shino glaze that
is nearly identical to the formula you use. I've encountered the same type
of cold looking Shino, white, pasty looking. It wasn't the entire piece but
maybe one side of the pot or a swath across a platter. I concluded and
mostly solved the problem with a heavier reduction at my reduction cone.
With my updraft I lit the second set of burners earlier into the firing
cycle to prevent cold air from being drawn into the kiln before reduction. I
changed my stacking arrangement so that the pots were not "exposed," near
the burner ports. I used cut soft firebrick to "deflect" some of the air and
gases being drawn into the kiln chamber. So far it has worked to solve most
of the problem. I say that because I can still see some evidence on a Shino
glazed pot in the problem area from the last firing that maybe one burner is
not performing as well as the other 9. Every so often an insect or a piece
of debris gets down in the burner interfering with the performance. My
burners face up into the bottom of the kiln so after each bisque firing I
shop vac them out. I still have some burner shutter adjustment that I can
work with to add into solving the problem for that area of the kiln. Overall
you have to keep your firing schedule closely the same to help diagnose
these problems.
Dale Tex
"across the alley from the Alamo"
Helotes, Texas USA
www.daleneese.com
Ingeborg Foco on mon 11 aug 08
Dale,
I fire with a downdraft kiln which has bag walls so the pots are protected
from direct flame.
I have been forced to disassemble my 4 burners prior to each firing to make
sure no lizards have
taken up housekeeping. It is a real PITA but unfortunately necessary. They
have even climbed in while
the firing is in progress (the air plates stay cool for a long time) In
other words,my burners are probably the cleanest burners in all of SW
Florida.
It's good to know that your glaze is very similar and that the problems are
related more to firing. I do keep extensive firing records and will go
back in time to see what is/went amiss. Thanks.
Ingeborg
thepottersworkshop.com
On Mon, Aug 11, 2008 at 10:32 AM, Dale Neese wrote:
> Ingeborg,
>
> I don't think it's the glaze that is the problem. I use a Shino glaze that
> is nearly identical to the formula you use. I've encountered the same type
> of cold looking Shino, white, pasty looking. " It wasn't the entire piece
> but
> maybe one side of the pot or a swath across a platter. I concluded and
> mostly solved the problem with a heavier reduction at my reduction cone.
> With my updraft I lit the second set of burners earlier into the firing
> cycle to prevent cold air from being drawn into the kiln before reduction.
> I
> changed my stacking arrangement so that the pots were not "exposed," near
> the burner ports. I used cut soft firebrick to "deflect" some of the air
> and
> gases being drawn into the kiln chamber. So far it has worked to solve most
> of the problem. I say that because I can still see some evidence on a Shino
> glazed pot in the problem area from the last firing that maybe one burner
> is
> not performing as well as the other 9. Every so often an insect or a piece
> of debris gets down in the burner interfering with the performance. My
> burners face up into the bottom of the kiln so after each bisque firing I
> shop vac them out. I still have some burner shutter adjustment that I can
> work with to add into solving the problem for that area of the kiln.
> Overall
> you have to keep your firing schedule closely the same to help diagnose
> these problems.
>
> Dale Tex
> "across the alley from the Alamo"
> Helotes, Texas USA
> www.daleneese.com
>
Des & Jan Howard on tue 12 aug 08
Ingeborg
Try refiring in an electric kiln. Our shinos fired to Cone 11/12+ in
reduction in a forced air kiln came out red-orange. The present
inspirated kiln fired to Cone 10+/12 reduction tend to come out
white,looking pretty much like the way you describe yours. Now,we build
up a collection from gas kiln firings,then electric fire them to 1040oC,
sit there for 4-6 hours then turn the kiln off.
Des
Ingeborg Foco wrote:
I am wondering if I am just to close to the situation and
> there is something very obvious and correctable that I am missing.
>
> I did not make it clear when I said I have to make a bunch more and toss the
> rest. I was referring to say an order of 6 mugs where I have to make a ton
> more and hope at least 6 come out. I don't throw the glaze out. I have
> though mixed a new batch to see if it reacts differently and unfortunately I
> had the same headache, pasty white pots that do not sell even if I mark them
> down.
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
Ingeborg Foco on tue 12 aug 08
Hi Des,
Thanks for the tip. I will definitely try that the next time I get some
pasty white pots. Unfortunately, I hammered a bunch just recently - trying
to clear my mind and my studio. My problem will be in holding the kiln at
that temp for 4-6 hours as my electric kilns are manual.
Ingeborg
On Tue, Aug 12, 2008 at 1:07 AM, Des & Jan Howard wrote:
> Ingeborg
> Try refiring in an electric kiln. Our shinos fired to Cone 11/12+ in
> reduction in a forced air kiln came out red-orange. The present
> inspirated kiln fired to Cone 10+/12 reduction tend to come out
> white,looking pretty much like the way you describe yours. Now,we build
> up a collection from gas kiln firings,then electric fire them to 1040oC,
> sit there for 4-6 hours then turn the kiln off.
> Des
>
>
> Ingeborg Foco wrote:
> I am wondering if I am just to close to the situation and
>
>> there is something very obvious and correctable that I am missing.
>>
>> I did not make it clear when I said I have to make a bunch more and toss
>> the
>> rest. I was referring to say an order of 6 mugs where I have to make a
>> ton
>> more and hope at least 6 come out. I don't throw the glaze out. I have
>> though mixed a new batch to see if it reacts differently and unfortunately
>> I
>> had the same headache, pasty white pots that do not sell even if I mark
>> them
>> down.
>>
>
>
> --
> Des & Jan Howard
> Lue Pottery
> Lue NSW
> Australia
> 2850
>
> 02 6373 6419
>
--
Sincerely,
Ingeborg
www.thepottersworkshop.com
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