Joyce Lee, Jim Lee on sun 1 dec 96
I am looking for a clear matt glaze cone 8-10 reduction. Is there such
an animal? I've looked in my library (not extensive but pretty good
for a novice}and on the Ceramics Web Glaze Database. If I work with a
glaze to which colorant must be added and do not add colorant, will that
glaze be clear? If the glaze is listed as matt, will the non-coloranted
form be a clear matt? Thank you. I will test anyway but advance info is
more than just nice.
Where are Francoise and June and Russell and Peggy and Rose etc etc etc?
I'm happy with our clayarters and they all know more than I do. I've
received such expert, compassionate and thorough advice from so many of
you, but I miss our absent members, too.
Joyce
Deserted in the desert
Ron Roy on mon 2 dec 96
>----------------------------Original message----------------------------
>I am looking for a clear matt glaze cone 8-10 reduction. Is there such
>an animal? I've looked in my library (not extensive but pretty good
>for a novice}and on the Ceramics Web Glaze Database. If I work with a
>glaze to which colorant must be added and do not add colorant, will that
>glaze be clear? If the glaze is listed as matt, will the non-coloranted
>form be a clear matt? Thank you. I will test anyway but advance info is
>more than just nice.
The only kind of clear (well semi clear) matt glazes are high calcium
glazes. There is good information In Ian Curries book "Stoneware Glazes"
and it is still available. Great book - anyone who high fires will get
their $ worth and more.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
June Perry on mon 2 dec 96
Dear Joyce:
I just sent the last of my company packing after five days of family fun and
games. So here is a recipe for a cone 10 clear matt. This is a wonderful,
buttery smooth clear glaze, as matt as you can probably get for a clear. I
have a couple of others that I recently designed but I don't have them in my
database yet. Try this one. I thin you'll like it. Unless you put opacifiers
in it it should stay transparent with the additions of most colorants.
#415 Clear Buttery Matt
85 Cornwall Stone
10 Whiting
5 Magnesium Carbonate
Regards,
June
David Hewitt on tue 3 dec 96
In message , "Joyce Lee, Jim Lee" writes
>----------------------------Original message----------------------------
>I am looking for a clear matt glaze cone 8-10 reduction. Is there such
>an animal?
I routinely use a glaze which I fire to cone 8 oxidation which is matt
and which I apply over coloured slips. These colours show through the
glaze, if that meets your requirement of 'clear'.
I use it over a buff stoneware and describe the colour as light oatmeal.
If an area is double dipped it comes out whiter so it is sensitive to
thickness and drips or runs want to be avoided unless the variation in
thickness and colour suits your pot.
If I fire above cone 8 it progresses to being shiny. I think it would
be the same in reduction.
The details are as follows:
RECIPE
50 Cornish Stone
22 China clay
23 Dolomite
6 Whiting
10 Talc
---
111 total
UNITY FORMULA
K2O .045 Al2O3 .346 SiO2 1.943
Na2O .071
MgO .442
CaO .442
COEFF of EXPANSION
McLindon 5.87 x 10 -6 C Linear or 2.93 x 10 -7 %
English & Turner 4.63 x 10 -6 C Linear or 2.31 x 10 -7 %
David Hewitt
David Hewitt
David Hewitt Pottery Caerleon, Tel:- 01633 420647
7 Fairfield Road, Caerleon, Newport, South Wales, UK.
URL http://digitalfire.com/magic/hewitt.htm
iandol on thu 19 dec 02
Dear Ababi,=20
A Glaze which is Matt and Clear is an interesting proposition whatever =
temperature it is intended to be fired at. Chappell lists a few but =
there seems to be no clear indication as to why they exhibit these =
qualities when others with similar content and composition do not.
If Matt means that it has a Surface Roughness which can be detected by =
touching or observed because there are no reflections from the surface =
and Clear means that it is as transparent as window glass or fresh water =
then the task is to suggest a mixture which allows both of these things =
to happen simultaneously. So this becomes a Glaze Design Problem.
As I understand things, glazes become matt either (a) when they start =
growing microscopic crystals or (b) when some ingredients do not =
dissolve into the vitreous melt and that glazes become clear when (c) =
all of the ingredients dissolve into the vitreous melt and (d) the melt =
cools so fast that crystallisation is suppressed so the result is a =
transparent layer on the clay.
I think the phrase now needed is about having one's cake and eating it!! =
Sort of being self contradictory.
Seems to me you are setting someone an otherwise impossible task by =
asking for such a beast without considering the conditions and internal =
processes under which such a glaze might be created and suggesting a =
group of materials which would accomplish the task.
By the way, I was under the impression that you could put such a =
question to any of the Glaze Calculation Programs, you know, type in the =
description of the glaze you need, name a cone value and wait for the =
print out. Or have I been deluded?=20
Best regards,
Ivor Lewis.
Ababi on thu 19 dec 02
Yes Ivor you are right!
In the last milenium when I learnt ceramics, there was in my school a mate clear for
low fire: My teacher bought from a supplier his gloss and his matte mixed them and
we had pretty nice matte clear at 1100C (around ^03).
Lately my good adviser at my supplier and friend too, Yehuda Koren gave me
examples of two new frits, among them this one:
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
FRIT Degussa 90368 100.0
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Seger Weight%
KNO 0.200 5.76%
CaO 0.700 18.24%
MgO 0.100 1.87%
Al2O3 0.250 11.83%
B2O3 0.200 6.47%
SiO2 2.000 55.83%
Na2O 0.200 5.76%
Al:Si 8.00
Expan. 8.13
ST 354.96
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Yehuda said; "Adding this frit to the glaze will make it matte clear". I did not like the
answer and asked for the analysis. I asked him lately what about ^6, he said they
were working on it in the polytechnic school he works in.
That was the moment to ask clayart for an advise, because to my humble knowledge
they still test there in the "good old way".
I got one answer explained my why probably it is impossible.
As I had a firing yesterday I tested three glazes: I took RR& J gloss liner and changed
the frit 3 different frits each time another one, with higher alumina ( 3134 has none)
and adjusted the silica to get sightly lower Si:Al relations.
When I will be done I will ask RR or John Hesslberth for permission to post it
(incase that I will have good results).
Your question about the fully automated software reminds of me this story:
There was a fully automated computed well programmed factory:
In front of the offices there was a big lawn with cows eating the green grass (I
think they were pretty high!)
There was a big vacuum machine that Swallowed the cows, very efficient! In the
other side you got ready to use : Steaks, meat balls as well as shoes! ( not to talk
about bone ash)!
One day they were infected by a new unknown computer virus, Oh My Goodness! The
shoes bone ash as well as the steaks ( and the meat balls too!) were Swallowed in
and from the front run out to the lawn happy cows!
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
and also
http://www.israel-ceramics.org/membersGallery/personalpage.asp?MID=507
---------- Original Message ----------
>Dear Ababi,
>A Glaze which is Matt and Clear is an interesting proposition whatever
>temperature it is intended to be fired at. Chappell lists a few but there seems to
>be no clear indication as to why they exhibit these qualities when others with
>similar content and composition do not.
>If Matt means that it has a Surface Roughness which can be detected by
>touching or observed because there are no reflections from the surface and
>Clear means that it is as transparent as window glass or fresh water then the task
>is to suggest a mixture which allows both of these things to happen
>simultaneously. So this becomes a Glaze Design Problem.
>As I understand things, glazes become matt either (a) when they start growing
>microscopic crystals or (b) when some ingredients do not dissolve into the
>vitreous melt and that glazes become clear when (c) all of the ingredients
>dissolve into the vitreous melt and (d) the melt cools so fast that crystallisation is
>suppressed so the result is a transparent layer on the clay.
>I think the phrase now needed is about having one's cake and eating it!! Sort of
>being self contradictory.
>Seems to me you are setting someone an otherwise impossible task by asking
>for such a beast without considering the conditions and internal processes under
>which such a glaze might be created and suggesting a group of materials which
>would accomplish the task.
>By the way, I was under the impression that you could put such a question to any
>of the Glaze Calculation Programs, you know, type in the description of the glaze
>you need, name a cone value and wait for the print out. Or have I been deluded?
>Best regards,
>Ivor Lewis.
>______________________________________________________________________________
>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.
Paul Lewing on thu 19 dec 02
on 12/18/02 8:10 PM, iandol at iandol@TELL.NET.AU wrote:
> By the way, I was under the impression that you could put such a =
> question to any of the Glaze Calculation Programs, you know, type in the =
> description of the glaze you need, name a cone value and wait for the =
> print out. Or have I been deluded?
Ivor, evidently you have been deluded. I'm familiar with most of the
programs out there on the market, and none of them will do what you suggest.
One of them (HyperGlaze) will give you some guidance once you have entered a
recipe as to what cone it might mature at, but it's a pretty broad
suggestion. Some, but not all, programs have a place that tells what cone a
particular recipe is fired to, but you have to tell it that information.
This is the kind of thing that many people wish a program would do for them,
but it's well-nigh impossible. Some glazes have a very broad firing range,
others do not. Then there are glazes that some people use at (for instance)
cone 3 as a matte glaze and others use at cone 6 as a glossy glaze. I'm
sure a number of these programmers would like to do such a thing, but there
are just too many variables.
The particular effect in question here, a clear matte glaze, is kind of a
Holy Grail of glaze-making. It's possible but very difficult, and such
glazes have a very narrow window in which they will be both clear and matte.
Some compromise in clarity or matteness is almost always necessary.
Paul Lewing, Seattle
Ababi on fri 20 dec 02
When I tell my friends I use ceramic software, for glazing this get the sa=
me
impression like Ivor, that's why I told you the story of the cows factory.=
I will tell you here about the three programs I have used:
The first, the Glaze simulator , first version.
Fraser had a tool that predicted the melting point.
After sometime I learnt that when the GS wrote ^2-^4 was in my kiln 3^ -^6=
or so,
I learnt also that a given glaze from my school that my teacher said was f=
or ^7
worked in ^03 too.
In the GS first version, was very hard to convert recipe from "your materi=
als" to
"mine". I am grateful to fraser, because this way I had to learn a lot abo=
ut the
materials!
Tony Hansen has written to me that you cannot predict maturing point. In m=
y level of
knowing (Glaze Addict) which is two degrees below glaze gurus I can predic=
t the
maturing of a glaze at ^6 in my kiln and if it will be matte or gloss.
Insight5 has a very interesting way to convert recipe, it is complicated t=
o explain I did
it once and do not want to repeat.
All three programs I have used, these days mainly Matrix2000 are guiding y=
ou with
limit tables, to achieve what you want. You can choose to work with any li=
mits you
want to, I use mainly R&J's foodsafe limits. As I have written before, the=
limits are a
guide. When I make a waxy glaze with 20% spodumen the computer does not sh=
ut
down and does not scream at me, it shows me in the graph, were are the lim=
its and
where I am: I am the one that click on the "Save" and on the "Print".
In Matrix there is a fully automated way to convert recipes, I don't use i=
t as it is a
machine work! ( remember the cows machine?) I might get weird results, pro=
per
chemically but wrong practically.
It has more ways, better ones, but this is not the point of this letter.
Many 04^ glazes I made worked in ^6 too, runnier but worked.
The only program if you can call it that gives you exact results is:
http://art.sdsu.edu/ceramicsweb/
Click on: ClayArt glazes
>-------------------------------------------------------------------------=
-------
>ClayArt Glaze Database Search Form
>Search for Glazes
>in the ClayArt Glaze Recipe database.
> Look Everywhere finds names in comments, ingredients, email addresses, c=
olor,
firing info, etc. It's a good choice for general searches but not for cone=
number
searching - use the cone field for that. All fields are optional, but you =
need to enter at
least one search key!
>
>Look Everywhere:
> equalsnot equalscontainsbegins withends with
>
>Glaze Name:
> equalsnot equalscontainsbegins withends with
>
>Color or Surface:
> equalsnot equalscontainsbegins withends with
>
>Cone:
> equalsnot equalscontainsbegins withends with
>
>Date:
> =3D!=3Dcontainsstarts withends with>> or =3D<< or =3D
>
>Thermal expansion:
> =3D!=3Dcontainsstarts withends with>> or =3D<< or =3Dx10-7/=B0C
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
and also
http://www.israel-ceramics.org/membersGallery/personalpage.asp?MID=3D507
---------- Original Message ----------
>on 12/18/02 8:10 PM, iandol at iandol@TELL.NET.AU wrote:
>> By the way, I was under the impression that you could put such a =3D
>> question to any of the Glaze Calculation Programs, you know, type in th=
e =3D
>> description of the glaze you need, name a cone value and wait for the =3D=
>> print out. Or have I been deluded?
>Ivor, evidently you have been deluded.
Ron Roy on fri 20 dec 02
There is only one type of transparent matte that I know of - high calcium -
slow cooling will help them develop - not really transparent - rather semi
transparent - most will mark from cutlery because of the less than glassy
surface.
RR
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ababi on sat 21 dec 02
Of course Ron The only glazes that pass the tests I learnt from you book (and John's
too) are for food surface.
To clayArters: Most of my glazes are decorative though I do not use poisonous
materials. The only exceptions: Lithium Carbonate for crystal glazes and spodumen
for waxy glazes. About the last ones I shall write you in a separate letter.
Not foodsafe for these of you that do not know can be with the most unpoisonous
materials if the glaze is not built properly according to the rules.
I used a glaze I told you once, with 40% soda bicarbonate, at that time I could not
understand what was the white stuff that covered the wares after some time and
appeared again after cleaning and I "knew": Only good stuff, clay, like in the garden
quartz like in the sea shore and soda bicarbonate like in the pancakes!
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
http://www.milkywayceramics.com/cgallery/asharon.htm
and also
http://www.israel-ceramics.org/membersGallery/personalpage.asp?MID=507
---------- Original Message ----------
most will mark from cutlery because of the less than glassy
>RR
>Ron Roy
>RR#4
>15084 Little Lake Road
>Brighton, Ontario
>Canada
>K0K 1H0
>Phone: 613-475-9544
>Fax: 613-475-3513
>______________________________________________________________________________
>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.
iandol on sun 22 dec 02
Dear Ron Roy,
Once again you raise points which lead to interesting questions <>There =
is only one type of transparent matte that I know of - high calcium =
-slow cooling will help them develop - not really transparent - rather =
semi transparent - most will mark from cutlery because of the less than =
glassy surface.<>
Given that the suggested limits for stoneware glazes include a max of =
0.7 Mol of CaO this effect, cutlery marking, is predictable when the =
limit is approached in a high Calcium glaze. Crystals which form have =
lowish Mohs hardness even if the glass is harder. Questions which come =
to mind relate to the notion of using much lower CaO values to ensure =
the growth of much harder (MH =3D,>6)crystals. But then it might be =
claimed that such a glaze would be unstable and soluble. The second =
question is how to maintain or ensure transparency.
Enjoy the week ahead.
Best regards,
Ivor
Ron Roy on thu 26 dec 02
Just to be clear on this - CaO is one of the best fluxing oxide for
promoting durability and hardness - we have one in our book for instance -
with 0.85 in the Seger formula - a stable semi matte - lab tested. If this
glaze is not slow cooled I don't think marking would be a problem.
Matte glazes tend to mark with cutlery because they are rough surfaced and
the metal gets abraded off because of this roughness. Some times the marks
are easily removed just by rubbing with a finger - other times they are
very difficult to remove.
We have to be careful when we say that saying within the limits will
automatically give durability. First it depends on which limits you use -
second - stable glazes can be made out side limits and third - staying
within limits is not a guarantee a glaze will be stable.
This is a complicated subject and in the end the only true way to determine
stability and durability is to have the glazes tested in lab capable of
analysing for leaching.
RR
>Once again you raise points which lead to interesting questions <>There is
>only one type of transparent matte that I know of - high calcium -slow
>cooling will help them develop - not really transparent - rather semi
>transparent - most will mark from cutlery because of the less than glassy
>surface.<>
>
>Given that the suggested limits for stoneware glazes include a max of 0.7
>Mol of CaO this effect, cutlery marking, is predictable when the limit is
>approached in a high Calcium glaze. Crystals which form have lowish Mohs
>hardness even if the glass is harder. Questions which come to mind relate
>to the notion of using much lower CaO values to ensure the growth of much
>harder (MH =,>6)crystals. But then it might be claimed that such a glaze
>would be unstable and soluble. The second question is how to maintain or
>ensure transparency.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
iandol on fri 27 dec 02
Dear Ron Roy,
Your remarks about knife or cutlery marks are interesting.
If the abrasive is harder than the steel then the steel is abraded.
If the steel is harder than the surface it contact then the surface is =
abraded.
So identifying the nature of the abrasive is important. A rough, Aka =
matt, surface can be abraded by the steel if the glass or the minerals =
which form the matting agent are softer than the steel. This might be =
the case if the minerals responsible for the mattness were Wollastonite =
or Anorthite. Continuous use would result in a dulling of the working =
surface in the well of a plate.
In the hypothetical scenario I painted where the volume of Calcium oxide =
were reduced then it is probable that the matting agent would be Quartz, =
much harder even than dead hard untempered steel. So the knife would be =
worn away in use and the surface and, except for particles of steel =
which might adhere, would remain pristine.
So although it is known that High Calcia hardens a glaze and enhances =
its durability, reducing Calcia may enhance the hardness even more.
Might I suggest that if the knife abrades the surface there is the =
possibility that the glaze has not matured.
Best regards,
Ivor Lewis
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