Wanda Holmes on mon 16 sep 02
Autumn, I added to tin to my original recipe using GlazeChem and the
amount needed to bring my original COE of 73.4x10e-7 down to below 70
was more than 10%. Based on math (not actual glaze testing) it seems it
may work when small adjustments are needed, but it likely to change the
character of the glaze significantly if a larger adjustment is needed.
Wanda
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG] On
Behalf Of David Hewitt
Sent: Sunday, September 15, 2002 11:17 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: COE - need help from glaze gurus
Autumn,
10e-7
Tin oxide is of course an opacifier but if that produces an acceptable
colour etc. then it should also be beneficial in reducing the glaze COE.
All those ceramists who list SnO2 give it a low coefficient, not just
Appen.
David
In message , Autumn Downey writes
>Hello David,
>
>Thanks for sharing the info and numbers - and provisos for the
>colouring oxides.
>
>Just wondering if tin with its low COE and negative number (according
>to
>Appen) would make it a good anti-crazing additive - if it worked with
the
>intended glaze colour
>
>Tin seems like a very "glaze-friendly material" - except for price.
>
>Autumn Downey
>
>
>
>
>
>>>
>>Both Mayer/Havas and Appen give figures for a number of colouring
>>oxides, but when you look at these they are not all in the same
>>relative order.
>>
>>The following table illustrates this.
>>The figures for Appen are % Mol Linear x10-7/oC
>>The figures for Mayer/Havas are % Wt. Cubic x 10-7/oC
>>there are not figures for Hamer but the colouring oxides are listed in
>>relative expansion from high to low.
>>
>>Appen Mayer/Havas Hamer
>>FeO 55 Cr2O3 5.1 Cr2O3
>>Fe2O3 55
>> CoO 4.4 CoO
>>CoO 50
>>NiO 50 TiO2 4.1
>>
>>CuO 30 Fe2O3 4.0 Fe2O3
>> NiO 4.0 NiO
>>TiO2 30-1.5(%SiO2-50) TiO2
>> MnO 2.2
>>SnO2 -45 CuO 2.2 MnO
>> CuO
>> FeO 2.0
>> SnO2 2.0 SnO2
>>
>>I hope that the tabs come out OK to make this readable.
>>
>>As you say, the amount of colouring oxides are small so any error
>>would not be that great. I still think, however, that it is better
>>practice to use English/Turner figures as they stand together with
>>Appen for any recipe that you are studying.
>>
>>I have built in all options into my Glaze Workbook, as also has
>>Matrix. All too often it would seem to be assumed that there is only
>>one set of figures for expansion calculations as they are often quoted
>>without reference and without units. A hobby-horse of mine, as you
>>know, so please bear with me. I am quite sure that COE calculations
>>can be extremely useful in indicating the direction of making a change
>>in a recipe, but I do not consider that any calculated COE figure,
>>regardless of which ceramist's coefficients you use, to be a precise
>>figure of the actual COE. Add to this ones experience of which COE
>>numbers fit a given clay body and you are getting somewhere.
>>
>>>Say CuO falls between Zinc at 7 and MgO at 4.0 (I'm making these up
>>>by th= e
>>>way) then we can assume CuO is about 5.2 - accurate enough because so
>>>little copper is usually used. Some lists have some of each so it is
>>>a wo= rk around.
>>>
>>>In fact Hamer says CuO is the same as MnO - big clue!
>>>
>>>After that all one needs to do is construct an experiment to see if
>>>coppe= r increases expansion or lowers it in a glaze (glossy) with an
>>>expansion of say 5.2. If it does not work then rethink.
>>>
>>>There have been comments that some colours seem to affect expansion
>>>in wa= ys we cannot account for - there needs to be some work done in
>>>this area - n= ot
>>>rocket science to find out some useful information.
>>>
>>>RR
>>>
>>>>John,
>>>>I am interested in finding a list of colorants exp/cont. Does this
>>>>exis=
>>>t?
>>>>
>>>>Thanks, John Britt
>>>
>>>
>>>Ron Roy
>>>RR#4
>>>15084 Little Lake Road
>>>Brighton, Ontario
>>>Canada
>>>K0K 1H0
>>>Phone: 613-475-9544
>>>Fax: 613-475-3513
>>
>>--
>>David Hewitt
>>David Hewitt Pottery ,
>>7 Fairfield Road, Caerleon, Newport,
>>South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
>>FAX:- +44 (0) 870 1617274
>>Web site http://www.dhpot.demon.co.uk
>>
>>______________________________________________________________________
>>_____
>___
>>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.
>>
>>
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
________________________________________________________________________
______
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.
Autumn Downey on tue 17 sep 02
Hi Wanda,
You are right; the tin might only be useful on borderline crazing. I
think the other ingredients might be more the cause. - but there is an
inherent difficulty in making an alkaline blue (and having soda etc. which
will want to increase the expansion).
Have you tried Tom Buck's suggested recipe?
Good luck!
Will miss some Clayart until I get to Sask - a 3 day drive, hopefully no
longer. (The idea is to look for another vehicle there - not on the way!)
Autumn
At 06:50 PM 2002-09-16 -0500, you wrote:
>Autumn, I added to tin to my original recipe using GlazeChem and the
>amount needed to bring my original COE of 73.4x10e-7 down to below 70
>was more than 10%. Based on math (not actual glaze testing) it seems it
>may work when small adjustments are needed, but it likely to change the
>character of the glaze significantly if a larger adjustment is needed.
>Wanda
>
>-----Original Message-----
>From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG] On
>Behalf Of David Hewitt
>Sent: Sunday, September 15, 2002 11:17 AM
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: COE - need help from glaze gurus
>
>
>Autumn,
>10e-7
>Tin oxide is of course an opacifier but if that produces an acceptable
>colour etc. then it should also be beneficial in reducing the glaze COE.
>All those ceramists who list SnO2 give it a low coefficient, not just
>Appen.
>
>David
>In message , Autumn Downey writes
>>Hello David,
>>
>>Thanks for sharing the info and numbers - and provisos for the
>>colouring oxides.
>>
>>Just wondering if tin with its low COE and negative number (according
>>to
>>Appen) would make it a good anti-crazing additive - if it worked with
>the
>>intended glaze colour
>>
>>Tin seems like a very "glaze-friendly material" - except for price.
>>
>>Autumn Downey
>>
>>
>>
>>
>>
>>>>
>>>Both Mayer/Havas and Appen give figures for a number of colouring
>>>oxides, but when you look at these they are not all in the same
>>>relative order.
>>>
>>>The following table illustrates this.
>>>The figures for Appen are % Mol Linear x10-7/oC
>>>The figures for Mayer/Havas are % Wt. Cubic x 10-7/oC
>>>there are not figures for Hamer but the colouring oxides are listed in
>
>>>relative expansion from high to low.
>>>
>>>Appen Mayer/Havas Hamer
>>>FeO 55 Cr2O3 5.1 Cr2O3
>>>Fe2O3 55
>>> CoO 4.4 CoO
>>>CoO 50
>>>NiO 50 TiO2 4.1
>>>
>>>CuO 30 Fe2O3 4.0 Fe2O3
>>> NiO 4.0 NiO
>>>TiO2 30-1.5(%SiO2-50) TiO2
>>> MnO 2.2
>>>SnO2 -45 CuO 2.2 MnO
>>> CuO
>>> FeO 2.0
>>> SnO2 2.0 SnO2
>>>
>>>I hope that the tabs come out OK to make this readable.
>>>
>>>As you say, the amount of colouring oxides are small so any error
>>>would not be that great. I still think, however, that it is better
>>>practice to use English/Turner figures as they stand together with
>>>Appen for any recipe that you are studying.
>>>
>>>I have built in all options into my Glaze Workbook, as also has
>>>Matrix. All too often it would seem to be assumed that there is only
>>>one set of figures for expansion calculations as they are often quoted
>
>>>without reference and without units. A hobby-horse of mine, as you
>>>know, so please bear with me. I am quite sure that COE calculations
>>>can be extremely useful in indicating the direction of making a change
>
>>>in a recipe, but I do not consider that any calculated COE figure,
>>>regardless of which ceramist's coefficients you use, to be a precise
>>>figure of the actual COE. Add to this ones experience of which COE
>>>numbers fit a given clay body and you are getting somewhere.
>>>
>>>>Say CuO falls between Zinc at 7 and MgO at 4.0 (I'm making these up
>>>>by th= e
>>>>way) then we can assume CuO is about 5.2 - accurate enough because so
>
>>>>little copper is usually used. Some lists have some of each so it is
>>>>a wo= rk around.
>>>>
>>>>In fact Hamer says CuO is the same as MnO - big clue!
>>>>
>>>>After that all one needs to do is construct an experiment to see if
>>>>coppe= r increases expansion or lowers it in a glaze (glossy) with an
>
>>>>expansion of say 5.2. If it does not work then rethink.
>>>>
>>>>There have been comments that some colours seem to affect expansion
>>>>in wa= ys we cannot account for - there needs to be some work done in
>
>>>>this area - n= ot
>>>>rocket science to find out some useful information.
>>>>
>>>>RR
>>>>
>>>>>John,
>>>>>I am interested in finding a list of colorants exp/cont. Does this
>>>>>exis=
>>>>t?
>>>>>
>>>>>Thanks, John Britt
>>>>
>>>>
>>>>Ron Roy
>>>>RR#4
>>>>15084 Little Lake Road
>>>>Brighton, Ontario
>>>>Canada
>>>>K0K 1H0
>>>>Phone: 613-475-9544
>>>>Fax: 613-475-3513
>>>
>>>--
>>>David Hewitt
>>>David Hewitt Pottery ,
>>>7 Fairfield Road, Caerleon, Newport,
>>>South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
>>>FAX:- +44 (0) 870 1617274
>>>Web site http://www.dhpot.demon.co.uk
>>>
>>>______________________________________________________________________
>>>_____
>>___
>>>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.
>>>
>>>
>
>--
>David Hewitt
>David Hewitt Pottery ,
>7 Fairfield Road, Caerleon, Newport,
>South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
>FAX:- +44 (0) 870 1617274
>Web site http://www.dhpot.demon.co.uk
>
>________________________________________________________________________
>______
>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.
>
>___________________________________________________________________________
___
>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.
>
>
| |
|
