Ron Roy on tue 20 jan 98
Hi John,
Just a couple of comments about this glaze before I sign off for a few weeks.
Your calculation is very similar to mine - when trying to determine the
durability however you should make the superpax/zircopax a phantom material
- ie not included in calculation - because it does not become part of the
glass -
So my calculation with pax in is very similar to yours-
with pax in
-----------------
F3134............... 1016.00 23.09%
NEPH SY............. 320.00 7.27%
WOLAST.............. 784.00 17.82%
EPK................. 900.00 20.45%
SILICA.............. 980.00 22.27%
=ZIRCOPAX............ 400.00 9.09%
----------
4400.00
FORMULA & ANALYSIS
------------------
*CaO........ .78 12.70%
MnO2....... .00 .01%
*MgO........ .03 .31%
*K2O........ .02 .43%
*Na2O....... .18 3.26%
Fe2O3...... .00 .17%
TIO2....... .00 .06%
B2O3....... .27 5.52%
AL2O3...... .34 10.05%
SiO2....... 3.51 61.31%
P2O5....... .00 .03%
ZrO2....... .17 6.14%
COST/KG 3.25
RATIO 10.37
EXPAN 386.25
WEIGHT 343.42
with pax out
-----------------
F3134............... 1016.00 23.09%
NEPH SY............. 320.00 7.27%
WOLAST.............. 784.00 17.82%
EPK................. 900.00 20.45%
SILICA.............. 980.00 22.27%
+ZIRCOPAX............ 400.00 9.09%
----------
4400.00
FORMULA & ANALYSIS
------------------
*CaO........ .78 14.00%
MnO2....... .00 .01%
*MgO........ .03 .34%
*K2O........ .02 .48%
*Na2O....... .18 3.60%
Fe2O3...... .00 .19%
TIO2....... .00 .07%
B2O3....... .27 6.10%
AL2O3...... .34 11.10%
SiO2....... 3.33 64.10%
P2O5....... .00 .03%
COST/KG 1.65
RATIO 9.82
EXPAN 408.62
WEIGHT 311.50
My comments on durability - Looking good but there is an oversupply of CaO.
Expansion is on the low side even without the pax - with the pax I would do
some testing for fit. If you use the same glaze inside and out then the
effect of the low expansion is counteracted - if it's not too low. Put a
low expansion glaze on the inside and a crazing glaze on the out side and
you are really are asking for trouble in the form of cracking teapots, mugs
and - well just about everything - eventually.
If it were my glaze I would try to get the expansion up a bit - notice my
scale is different from everyone else's - it's a long story - but also
realize - none of them are accurate - none - my dilatometer tells me so.
They are useful (calculated expansion #'s) only in helping us tell if we
are going in the right direction - up or down. Anyway I would feel better
if the expansion was closer to 450.0 on my scale
RR revision to improve expansion
-----------------
F3134............... 21.00 19.09%
NEPH SY............. 19.00 17.27%
WOLAST.............. 20.00 18.18%
EPK................. 16.00 14.55%
SILICA.............. 24.00 21.82%
+ZIRCOPAX............ 10.00 9.09%
----------
110.00
FORMULA & ANALYSIS
------------------
*CaO........ .73 13.21%
MnO2....... .00 .01%
*MgO........ .03 .35%
*K2O........ .03 .97%
*Na2O....... .21 4.21%
Fe2O3...... .00 .15%
TIO2....... .00 .05%
B2O3....... .22 5.00%
AL2O3...... .34 11.14%
SiO2....... 3.36 64.92%
P2O5....... .00 .02%
COST/KG 1.51
RATIO 9.91
EXPAN 447.20
WEIGHT 310.44
Thanks for posting this glaze John - I am sure it will be most interesting
to those who want a "water clear" glaze - don't forget to leave the pax out
though. No! I am not sure my revision will be that clear and testing is the
ONLY way to find out.
I think you should also post your firing schedule - and for those of you
who are trying to get a clear glaze - mix it well.
There is a good way to find out if sieving a glaze makes it better or not -
try it different ways. I'm not trying to start anything here - it is true
that some glazes - unsieved - are not as good looking as the sieved
version. I have tried on several occasions to mix with a blender - dipped
some tiles and then sieved the glaze and dipped again - I did find a
difference - I also made a note to try the blender at different amounts of
time - just to see how long a glaze needed to be blended to equal the
sieving.
>----------------------------Original message----------------------------
>Hi Ron,
>
>Post's PMSP-4 glaze is mine, but the recipe you listed isn't correct. I
>submitted it to the the glazebase a while back and somehow it got posted
>incorrectly. I sent an e-mail to Richard Burkett about the problem some
>time ago. I'm not sure what happened after that. Anyway, here is the
>correct recipe with some of the variations that I use...
>
>+++++++++++++++++++++++
>+++ PMSP 4 Base +++
>+++++++++++++++++++++++
>
>Range: 6-8
>Firing type: Oxidation
>Glaze type: Stoneware
>Surface: Gloss
>Testing: Personal Favorite
>Date: 11/12/96
>
> Frit 3134 1016 25.4%
> Nepheline syenite 320 8 %
> Wollastonite 784 19.6%
> EPK 900 22.5% Hazard!
> Flint 980 24.5% Hazard!
> -------- ------
> 4000 100 %
>
> Superpax 400 10 %
Chemical Analysis
>===========================
>
> Na2O 0.18 Al2O3 0.35 SiO2 3.44
> K2O 0.01 B2O3 0.27 ZrO2 0.17
> MgO 0.02
> CaO 0.79
>
> Alumina:Silica ratio is 1.00 : 9.91
> Neutral:Acid ratio is 1.00 : 5.86
> Alkali:Neutral:Acid ratio is 1.00 : 0.62 : 3.61
>
>Expansion coefficient: 68.9 x 10e-7 per degree C
>Oxides causing abnormal expansion effects: B2O3
Ron Roy
93 Pegasus Trail
Scarborough,Canada
M1G 3N8
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
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