Alisha Clarke on tue 20 nov 07
Ron,
Out of curiosity I ran the same glaze in GlazeChem to see if they yield the
same analysis. The chemical analysis is virtually identical, but the
expansion is stated differently. In GlazeChem it states: "Expansion: 73.5 x
10e-7 per degree C".
In my very limited experience with glaze calculation, I've ignored the
expansion since I don't know how to interpret it for fit with a particular
clay body other than as a comparison of two glazes to see which one has
greater or lesser expansion.
What is the unit of measurement in your program, and how does it compare to
the results I'm getting? Is there a normal range (limit formula) for
expansion for cone 6 and for cone 10 clays that we can watch for to have an
idea in advance of whether it would fit?
Thanks,
Leesh
~~~~~~~~~~~~~~~~~~~~~~~~~
Alisha Clarke
Pottery by Leesh: www.alishaclarke.com
Pottery Basics: www.potterybasics.com
On Nov 19, 2007 9:06 PM, Ron Roy wrote:
> Hi John,
>
> Here you go - let me know if it needs some adjustment - there is a lot
> more
> raw clay but also some frit to help melt it - hard to tell if it will
> balance out.
>
> It's really close in all respects - I will be surprised if it's not a good
> sub.
>
> -----------------
> F3134............... 27.00
> TALC................ 3.00
> WHITING............. 19.00
> NEPH SY............. 6.00
> EPK................. 19.50
> SILICA.............. 25.50
> ----------
> 100.00
> FORMULA & ANALYSIS
> ------------------
> *CaO........ .78 18.32%
> MnO2....... .00 .01%
> *MgO........ .07 1.10%
> *K2O........ .01 .40%
> *Na2O....... .15 3.83%
> Fe2O3...... .00 .21%
> TIO2....... .00 .07%
> B2O3....... .24 7.05%
> AL2O3...... .23 9.88%
> SiO2....... 2.35 59.12%
> P2O5....... .00 .03%
>
> RATIO 10.17 (original is 10.16)
> EXPAN 478.85 (original is 477.15)
> WEIGHT 238.13
>
> RR
>
> >>> Hi John,
> >>>
> >>> Wana try a version using 3134? Be glad to convert it if you do the
> >>> testing
> >>> - anyone else interested?
> >>>
> >>> RR
> >>>
> >>> >I have been doing some test glazes - new glazes entirely, mixes of
> old
> >>> >glazes and new, and layering of one glaze over another. Results have
> >>> >been interesting, but one was outstanding. It came about as the
> result
> >>> >of layering Chrome Tin Red over MC6 Floating Green on C5 B-Mix. The
> >>> >result was so striking, that I decided to play with a specific glaze
> >>> for
> >>> >the color. I began by comparing the ingredients of Chrome Tin and MC6
> >>> >Floating Green and found they both had the same chemicals - only the
> >>> >amounts varied a bit. The one thing that the MC6 Floating Green had
> >>> that
> >>> >the Chrome Tin didn't was Cobalt Oxide. I decided to go with the
> Chrome
> >>> >Tin and added 1% Cobalt Oxide. When applied by dipping, the results
> was
> >>> >a stunning solid purple ever so slightly on the lavender side. I'm
> sure
> >>> >that by varying the amount of cobalt just a tiny bit, one could go a
> >>> >brighter lavender, or a darker purple. But the combination of tin,
> >>> >chromium, and cobalt seems to produce a good solid color rather than
> >>> the
> >>> >multiple colors of the straight chrome-tin combination. So if a solid
> >>> >purple is your desire, you might try this.
> >>> >
> >>> >Chrome-Tin Purple Glaze
> >>> >Cone 5-6 (#5 witness cone bent to tip touching shelf in my kiln)
> >>> >(as applied to C5 Laguna B-mix)
> >>> >Gloss
> >>> >
> >>> >Base Glaze-------
> >>> >Silica (200) - 32%
> >>> >Gerstley Borate - 21%
> >>> >Calcium Carbonate (Whiting) - 20%
> >>> >Nepheline Syenite - 16%
> >>> >Edgar Plastic Kaolin (EPK) - 11%
> >>> >Total: -100%
> >>> >
> >>> >Colors ------red/pink/purple/mauve
> >>> >Add:
> >>> >Tin Oxide - 5%
> >>> >Chromium Oxide - 0.2%
> >>> >
> >>> >For a consistent solid purple with slight lavender hue -
> >>> >Add:
> >>> >Cobalt oxide - 1%
> >>> >
> >>> >Notes: color and hue in the purple range can be varied by varying the
> >>> >amount of Cobalt Oxide - your choice. Test, test, test!
> >>> >
> >>> >Caution: Cobalt Oxide is slightly toxic until bound with glass
> >>> formers..
> >>> >Handle only with gloves and mask.
> >>> >
> >>> >Regards,
> >>> >
> >>> >John Rodgers
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
>
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
--
John Sankey on wed 21 nov 07
Typical pottery clays have a thermal expansion of 6x10^-6/K, that
is their length increases by 6 parts per million per metric
degree temperature rise. Metric degrees are expressed in Kelvin,
the absolute thermodynamic scale; one Kelvin equals a Celsius
degree. International metric standards call for the use of
exponents in factors of three: 10^-3 (milli), 10^-6 (micro) etc.
So, if you see a calculated glaze expansion of 73, it needs to be
divided by 10 to put it into proper metric units; 500 needs to be
divided by 100
Just as important is knowing which oxide expansion numbers are
used by the program, and how. In the case of one program
available as trialware, which offered various authors as options
for coefficients, it appears it used each authors' values for the
oxides they studied and zero for all the others. The results were
useless even for comparing glazes.
You shouldn't use any calculated expansion unless the program
writer is willing to specify the expansion values it uses. See
http://sankey.ws/glazeexpansion.html
for a summary of the data available and what I recommend glaze
calculation programs use.
--
Include 'Byrd' in the subject line of your reply
to get through my spam filter.
John Hesselberth on thu 22 nov 07
On Nov 21, 2007, at 10:45 AM, John Sankey wrote:
> You shouldn't use any calculated expansion unless the program
> writer is willing to specify the expansion values it uses. See
> http://sankey.ws/glazeexpansion.html
> for a summary of the data available and what I recommend glaze
> calculation programs use.
I agree that it is somewhat confusing as to how the various authors
of glaze calculation software calculate expansion and what
coefficients they use. Some seem to be hard-wired behind the scenes
so you can't do anything but guess. Just to try to be clear on how I
decided to handle this issue in GlazeMaster, here is what I did.
First any material listed as an ingredient is included in the
calculation. Any shown as additives are not. So if you have a lot of
iron in a recipe you should probably list it as an ingredient rather
than an additive. The choice is yours.
Second, I made provision for including coefficients for Li2O, Na2O,
K2O, MgO, CaO, SrO, BaO, ZnO, PbO, Al2O3, B2O3, Fe2O3, SiO2, TiO2,
and P2O5. I decided to ignore things like the oxides of Co, Cu, Ni,
Mn and other minor oxides because of the paucity of data and the fact
that they are usually used in such small quantities.
Third I put in 3 sets of coefficients which are fully described in
the User's Guide but are also user modifiable. If you don't like the
ones I have, use your own. I did decide to leave all the units and
the 10 to the minus 6 or 7 or 8 off of the program displays because
that is of little use to the practicing potter. Most potters get
used to using one set of coefficients and knowing whether the
calculated expansion is 63 or 75 is all they really want or need to
know. The User's Guide does, however, have an explanation of units.
Fourth, I put in a provision to toggle between sets of units on all
of the recipe pages. That way if you like West and Gerrow units but
you are talking to Ron Roy who prefers modified English and Turner
units you can quickly toggle to numbers he relates to.
Lastly, I'd like to make the point that the rule of mixtures which is
used to calculate coefficients of thermal expansion for glazes is
itself a simplified algorithm for a complex system. It is probably no
better than the perfect gas law is at predicting PVT relationships
for gases. So it usually doesn't pay to try worry about more than 2
significant figures for COE calculations. But like most authors I
have shown more and am continually surprised by requests for even
more than I show in various parts of GlazeMaster.
Happy Thanksgiving to everyone in the US. It's my turn to cook this
week and the turkey just went in the oven.
Regards,
John
John Hesselberth
www.frogpondpottery.com
"Man is a tool-using animal....without tools he is nothing, with
tools he is all" .... Thomas Carlyle
Ron Roy on thu 22 nov 07
Hi Alisha,
Unfortunatly there are several different numbers being used - and it is
confusing. I have tried to make some comparisons but they don't work very
well.
You will have to learn to use what you have - know what number you get from
crazing glazes and non crazing glazes - list them in order of increasing or
decreasing and note where the crazing stops - on each of the clays you use.
You will then know approximately what number to use to have a glaze that
does not craze on the different clays you use.
Once you start noticing the calcualted expansion numbers you will start
using them.
Perhaps the work that John Sankey is doing will result in a univerally
acceptable system and we will all start using it.
If you have a copy of our book - see chapter 5 - the fit testing glazes -
they all have 3 different fit calculation numbers - and - an actual
measured expansion number. That will help you understand it.
RR
>Ron,
>Out of curiosity I ran the same glaze in GlazeChem to see if they yield the
>same analysis. The chemical analysis is virtually identical, but the
>expansion is stated differently. In GlazeChem it states: "Expansion: 73.5 x
>10e-7 per degree C".
>
>In my very limited experience with glaze calculation, I've ignored the
>expansion since I don't know how to interpret it for fit with a particular
>clay body other than as a comparison of two glazes to see which one has
>greater or lesser expansion.
>
>What is the unit of measurement in your program, and how does it compare to
>the results I'm getting? Is there a normal range (limit formula) for
>expansion for cone 6 and for cone 10 clays that we can watch for to have an
>idea in advance of whether it would fit?
>Thanks,
>Leesh
>~~~~~~~~~~~~~~~~~~~~~~~~~
>Alisha Clarke
>Pottery by Leesh: www.alishaclarke.com
>Pottery Basics: www.potterybasics.com
>
>On Nov 19, 2007 9:06 PM, Ron Roy wrote:
>
>> Hi John,
>>
>> Here you go - let me know if it needs some adjustment - there is a lot
>> more
>> raw clay but also some frit to help melt it - hard to tell if it will
>> balance out.
>>
>> It's really close in all respects - I will be surprised if it's not a good
>> sub.
>>
>> -----------------
>> F3134............... 27.00
>> TALC................ 3.00
>> WHITING............. 19.00
>> NEPH SY............. 6.00
>> EPK................. 19.50
>> SILICA.............. 25.50
>> ----------
>> 100.00
>> FORMULA & ANALYSIS
>> ------------------
>> *CaO........ .78 18.32%
>> MnO2....... .00 .01%
>> *MgO........ .07 1.10%
>> *K2O........ .01 .40%
>> *Na2O....... .15 3.83%
>> Fe2O3...... .00 .21%
>> TIO2....... .00 .07%
>> B2O3....... .24 7.05%
>> AL2O3...... .23 9.88%
>> SiO2....... 2.35 59.12%
>> P2O5....... .00 .03%
>>
>> RATIO 10.17 (original is 10.16)
>> EXPAN 478.85 (original is 477.15)
>> WEIGHT 238.13
>>
>> RR
>>
>> >>> Hi John,
>> >>>
>> >>> Wana try a version using 3134? Be glad to convert it if you do the
>> >>> testing
>> >>> - anyone else interested?
>> >>>
>> >>> RR
>> >>>
>> >>> >I have been doing some test glazes - new glazes entirely, mixes of
>> old
>> >>> >glazes and new, and layering of one glaze over another. Results have
>> >>> >been interesting, but one was outstanding. It came about as the
>> result
>> >>> >of layering Chrome Tin Red over MC6 Floating Green on C5 B-Mix. The
>> >>> >result was so striking, that I decided to play with a specific glaze
>> >>> for
>> >>> >the color. I began by comparing the ingredients of Chrome Tin and MC6
>> >>> >Floating Green and found they both had the same chemicals - only the
>> >>> >amounts varied a bit. The one thing that the MC6 Floating Green had
>> >>> that
>> >>> >the Chrome Tin didn't was Cobalt Oxide. I decided to go with the
>> Chrome
>> >>> >Tin and added 1% Cobalt Oxide. When applied by dipping, the results
>> was
>> >>> >a stunning solid purple ever so slightly on the lavender side. I'm
>> sure
>> >>> >that by varying the amount of cobalt just a tiny bit, one could go a
>> >>> >brighter lavender, or a darker purple. But the combination of tin,
>> >>> >chromium, and cobalt seems to produce a good solid color rather than
>> >>> the
>> >>> >multiple colors of the straight chrome-tin combination. So if a solid
>> >>> >purple is your desire, you might try this.
>> >>> >
>> >>> >Chrome-Tin Purple Glaze
>> >>> >Cone 5-6 (#5 witness cone bent to tip touching shelf in my kiln)
>> >>> >(as applied to C5 Laguna B-mix)
>> >>> >Gloss
>> >>> >
>> >>> >Base Glaze-------
>> >>> >Silica (200) - 32%
>> >>> >Gerstley Borate - 21%
>> >>> >Calcium Carbonate (Whiting) - 20%
>> >>> >Nepheline Syenite - 16%
>> >>> >Edgar Plastic Kaolin (EPK) - 11%
>> >>> >Total: -100%
>> >>> >
>> >>> >Colors ------red/pink/purple/mauve
>> >>> >Add:
>> >>> >Tin Oxide - 5%
>> >>> >Chromium Oxide - 0.2%
>> >>> >
>> >>> >For a consistent solid purple with slight lavender hue -
>> >>> >Add:
>> >>> >Cobalt oxide - 1%
>> >>> >
>> >>> >Notes: color and hue in the purple range can be varied by varying the
>> >>> >amount of Cobalt Oxide - your choice. Test, test, test!
>> >>> >
>> >>> >Caution: Cobalt Oxide is slightly toxic until bound with glass
>> >>> formers..
>> >>> >Handle only with gloves and mask.
>> >>> >
>> >>> >Regards,
>> >>> >
>> >>> >John Rodgers
>>
>> Ron Roy
>> RR#4
>> 15084 Little Lake Road
>> Brighton, Ontario
>> Canada
>> K0K 1H0
>>
>>
>>
>>__________________________________________________________________________
>>____
>> Clayart members may send postings to: clayart@lsv.ceramics.org
>>
>> You may look at the archives for the list, post messages, or change your
>> subscription settings here: http://www.acers.org/cic/clayart/
>>
>> Moderator of the list is Mel Jacobson who may be reached at
>> melpots2@visi.com
>>
>
>
>
>--
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, or change your
>subscription settings here: http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Alisha Clarke on sun 25 nov 07
Thank you John Sankey, Ron Roy, John Hesselberth and all of the other glaze
experts here. You all provide a fantastic service and I'm learning a lot
from you (but still have a lot to learn). I do have the MC6G book and was
planning to read it again.
Leesh
~~~~~~~~~~~~~~~~~~~~~~~~~
Alisha Clarke
Pottery by Leesh: www.alishaclarke.com
Pottery Basics: www.potterybasics.com
On Nov 22, 2007 3:52 PM, John Hesselberth wrote:
> On Nov 21, 2007, at 10:45 AM, John Sankey wrote:
>
> > You shouldn't use any calculated expansion unless the program
> > writer is willing to specify the expansion values it uses. See
> > http://sankey.ws/glazeexpansion.html
> > for a summary of the data available and what I recommend glaze
> > calculation programs use.
>
> I agree that it is somewhat confusing as to how the various authors
> of glaze calculation software calculate expansion and what
> coefficients they use. Some seem to be hard-wired behind the scenes
> so you can't do anything but guess. Just to try to be clear on how I
> decided to handle this issue in GlazeMaster, here is what I did.
>
> First any material listed as an ingredient is included in the
> calculation. Any shown as additives are not. So if you have a lot of
> iron in a recipe you should probably list it as an ingredient rather
> than an additive. The choice is yours.
>
> Second, I made provision for including coefficients for Li2O, Na2O,
> K2O, MgO, CaO, SrO, BaO, ZnO, PbO, Al2O3, B2O3, Fe2O3, SiO2, TiO2,
> and P2O5. I decided to ignore things like the oxides of Co, Cu, Ni,
> Mn and other minor oxides because of the paucity of data and the fact
> that they are usually used in such small quantities.
>
> Third I put in 3 sets of coefficients which are fully described in
> the User's Guide but are also user modifiable. If you don't like the
> ones I have, use your own. I did decide to leave all the units and
> the 10 to the minus 6 or 7 or 8 off of the program displays because
> that is of little use to the practicing potter. Most potters get
> used to using one set of coefficients and knowing whether the
> calculated expansion is 63 or 75 is all they really want or need to
> know. The User's Guide does, however, have an explanation of units.
>
> Fourth, I put in a provision to toggle between sets of units on all
> of the recipe pages. That way if you like West and Gerrow units but
> you are talking to Ron Roy who prefers modified English and Turner
> units you can quickly toggle to numbers he relates to.
>
> Lastly, I'd like to make the point that the rule of mixtures which is
> used to calculate coefficients of thermal expansion for glazes is
> itself a simplified algorithm for a complex system. It is probably no
> better than the perfect gas law is at predicting PVT relationships
> for gases. So it usually doesn't pay to try worry about more than 2
> significant figures for COE calculations. But like most authors I
> have shown more and am continually surprised by requests for even
> more than I show in various parts of GlazeMaster.
>
> Happy Thanksgiving to everyone in the US. It's my turn to cook this
> week and the turkey just went in the oven.
>
> Regards,
>
> John
>
>
> John Hesselberth
> www.frogpondpottery.com
>
> "Man is a tool-using animal....without tools he is nothing, with
> tools he is all" .... Thomas Carlyle
>
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
--
| |
|
