Dave Finkelnburg on tue 31 oct 00
Les,
Thanks for the detailed message!
You asked: "Why do I still see crazing at ridiculously low c.o.e's?"
>From my honest perspective, not having put all the work and effort you
obviously have into this, I have to say if the glaze crazes, its expansion
is greater than that of the clay body. Simple. Nothing else makes sense.
I ran your recipe CR#2A through my version of Insight. I'd say the
expansion is a lot closer to 600 than the 312 your version calculates. It
appears to me there's an error somewhere in your Material Data Table. We
need someone who really understands this to double check what I have done.
If the Insight MDT is corrupted, you can get funny numbers. This may be
what's happening.
It does make sense, since you still are seeing crazing on the tiles.
I do the freeze/boil test on my tiles. The good glaze fit tiles just
don't craze, the bad ones show up right away, some are in between.
You asked about shivering. I've seen it more than once. Makes a grown
person weep to take great pots and smash 'em with a hammer because the glaze
is shivering. It absolutely doesn't look like crazing. The glaze flakes
off the pot, usually on the rim. You can pick at it with a knife blade and
get flakes of the glaze. In really bad cases, it will literally leap off
the pot. No, the cracks have to be crazing.
I hope you get this figured out soon. I appreciate you keeping me
posted.
Dave Finkelnburg, trying to pretend it really isn't snowing
outside, again today
Les Wright on tue 31 oct 00
SET FONT -COURIER NEW -13PT =
Dear Dave,
In response to your query about what c.o.e units I used to determine the =
c.o.e
numbers for the different clays and glazes I tested. The c.o.e numbers fo=
r
both came from Ron Roy. Although only a guess, I think he uses English an=
d
Turner, x10-8/*c-%Wt-linear. The glaze calculation program that I use is
Insight and if you go to www.digitalfire.com you can download his databa=
se
for use with Insight. - for free. It is named riul00.tmt. Ron uses a
dilatometer to measure the c.o.e of the various bodies I used for my test=
s.
So, the clay c.o.e was measured and not calculated. The c.o.e's of my gla=
ze
tests are calculated. You are correct with regard to the porcelain and
stoneware bodies having a different c.o.e. The white stoneware bodies th=
at I
used had a c.o.e of 500, while the porcelains were 450.
The visual and textual qualities, of the glaze tests to date, are consist=
ent
with the original LREV C test. The glaze remains clear, so MgO is not a
problem, yet! Thanks for the heads-up. =
Moving on, I now believe my fit testing procedure may be the culprit. I t=
ested
the glaze fit by placing the tiles into a preheated oven. First, I heated=
the
oven to 110*c then inserted my test tiles until the oven again reached
temperature and held them at this temperature for about 20 minutes. I the=
n
submerged the tiles into 20*c water removing them after they reached room=
temperature. Taking a jeweler's magnifying glass, I looked for signs of
crazing. If no crazing was observed, I increased the temperature of the o=
ven
10*c and repeated the process. I continued, testing each tile, unless it=
had
crazed at a lower temperature, until reaching 180*c. If the glaze does no=
t
craze at 180*c supposedly, it will last years or forever without crazing.=
I am
sure you are aware of this method but I wanted you to know, step by step,=
how
I conducted these tests. Of course, all of the tests crazed. Yet, some ma=
de it
to 160*c before they succumbed to the cruel force. =
I talked to Ron about my problem, he suggested that I put the tests in a =
cold
oven (not preheated) and bring the temperature up slowly. Because he has
worked with MCS porcelain and knows its c.o.e, it was suggested that an
expansion of 440 - 445 should be fine. I tried his way and there was no
change, the crazing is still there. =
The other common method of testing for glaze fit is the freezing to boili=
ng
water test. You first place your tiles into the freezer for at least 24 h=
ours
and then plunge them into boiling water. Here again, I found there were
variations in what to do after the freezing period. Some simply dip their=
tiles into the boiling water three times.
Of the two testing procedures, oven and freezer, I have been told that th=
e
"oven method" is best for craze testing while the "freezer method" was be=
tter
suited to test for shivering.
I never went back and made the series of tests over again, I just felt th=
at I
was in some "black hole." I am not great at building mechanical devises
capable of indicating which direction, up or down, the c.o.e should read.=
=
As you know, I have no trouble (I think) with using the various glaze
calculation programs, after all, it's all just self-serve math. The ques=
tions
I would like you to answer for me are: Why do I still see crazing at
ridiculously low c.o.e's? Does the lean toward shivering have the same ef=
fect
with regard to the observed physical qualities of the glaze? Badly put. W=
ould
you expect, tiles that were exhibiting crazing and those showing signs of=
shivering to look the same?
For instance, are craze lines more vertical in nature and the tendency fo=
r
line fractures, tending toward shivering, more lateral? I could keep brin=
ging
the c.o.e down and have the glaze flake off the pot, but it seems nutty t=
o me.
After all, I know the c.o.e should to around 440 for this MCS porc. body.=
=
The last question, how do you test for glaze fit? Pleas tell me, step by =
step,
don't leave anything out. =
Anyway that's enough for now. Sorry I was so long in both this message an=
d the
length of time I took to reply.
Yours, Leslie Wright
Blessed are those who walk around in circles
for they will become big wheels.
SET FONT COURIER NEW - 13PT.
These are the series of tests carried out to lower the c.o.e of LREV C. A=
ll
retained the original test's visual and surface qualities. None showed si=
gns
of flaking, just lateral of vertical fractures associated with crazing.
Two Recipes: FILES SAVE AS - LREV C LREV CA
IN ORDER OF C.O.E LREV C LREV CA
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
G-200 FELDSPAR G200. 32.00 16.00% 31.59 15.79%
WOLLASTONITE........ 28.00 14.00% 27.64 13.82%
F12 (FERRO3134)..... 24.00 12.00% 23.69 11.85%
STRONTIUM CARBONATE. 20.00 10.00% 19.74 9.87%
TALC................ 4.00 2.00% 3.95 1.97%
EPK KAOLIN.......... 48.00 24.00% 47.38 23.69%
SILICA.............. 44.00 22.00% 46.01 23.00%
=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=
=3D=3D
200.00 200.00
CaO 0.53* 9.30% 0.53* 9.17%
MnO2 0.00 0.00% 0.00 0.00%
MgO 0.07* 0.90% 0.07* 0.89%
K2O 0.07* 1.94% 0.07* 1.92%
Na2O 0.10* 1.90% 0.10* 1.88%
Fe2O3 0.00 0.22% 0.00 0.22%
TIO2 0.00 0.08% 0.00 0.07%
B2O3 0.14 2.98% 0.14 2.94%
AL2O3 0.41 13.14% 0.41 12.96%
SiO2 3.31 61.97% 3.38 62.50%
P2O5 0.00 0.03% 0.00 0.03%
SrO 0.23* 7.54% 0.23* 7.44%
COST/KG 2.52 2.50
Si:Al 8.02 8.20
SiB:Al 8.35 8.53
EXPAN 445.51 440.06
Two Recipes: FILED AS: CR #1 & ADJGL1-ADJUSTED GLAZE ONE
IN ORDER OF C.O.E LREV CB LREV CC =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
G-200 FELDSPAR G200. 31.37 15.69% 32.69 16.34%
F12 (FERRO3134)..... 23.53 11.76% 25.46 12.73%
STRONTIUM CARBONATE. 19.61 9.80% 20.12 10.06%
EPK KAOLIN.......... 47.06 23.53% 45.64 22.82%
SILICA.............. 55.39 27.70% 55.81 27.90%
MAGNESIUM CARBONATE. 6.31 3.16%
DOLOMITE............ 19.12 9.56% 13.97 6.98%
TALC................ 3.92 1.96%
=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=
=3D=3D
200.00 200.00
CaO 0.36* 6.39% 0.31* 5.54%
MnO2 0.00 0.00%
MgO 0.23* 2.92% 0.27* 3.37%
K2O 0.07* 2.00% 0.07* 2.08%
Na2O 0.10* 1.92% 0.11* 2.05%
Fe2O3 0.01 0.27% 0.00 0.25%
TIO2 0.00 0.08% 0.00 0.08%
B2O3 0.14 3.05% 0.15 3.31%
AL2O3 0.41 13.23% 0.41 13.10%
SiO2 3.32 62.39% 3.30 62.25%
P2O5 0.00 0.03% 0.00 0.03%
SrO 0.24* 7.72% 0.24* 7.95%
COST/KG 2.49 2.81
Si:Al 8.02 8.08
SiB:Al 8.35 8.45
EXPAN 412.88 410.58
Two Recipes: FILED AS CR#2 CR#3
IN ORDER OF C.O.E LREV CD LREV CE
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
STRONTIUM CARBONATE. 18.35 9.18% 21.51 10.75%
SILICA.............. 57.77 28.89% 68.82 34.41%
G-200 FELDSPAR G200. 35.57 17.78%
CADYCAL............. 13.56 6.78% 5.38 2.69%
DOLOMITE............ 26.68 13.34%
TILE #6 KAOLIN...... 48.07 24.03%
WOLLASTONITE........ 19.35 9.68%
F12 (FERRO3134)..... 15.05 7.53%
TALC................ 4.30 2.15%
EPK KAOLIN.......... 58.06 29.03%
MAGNESIUM CARBONATE. 7.53 3.76%
=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=
=3D=3D
200.00 200.00
CaO 0.43* 7.49% 0.43* 7.28%
MnO2 0.00 0.00%
MgO 0.27* 3.39% 0.24* 2.94%
K2O 0.03* 0.78% 0.00* 0.13%
Na2O 0.04* 0.79% 0.05* 0.92%
Fe2O3 0.00 0.20% 0.01 0.26%
TIO2 0.02 0.41% 0.00 0.09%
B2O3 0.17 3.71% 0.16 3.35%
AL2O3 0.44 14.09% 0.40 12.40%
SiO2 3.30 61.53% 3.56 64.15%
P2O5 0.00 0.11% 0.00 0.03%
SrO 0.23* 7.50% 0.27* 8.43%
COST/KG 2.36 2.70
Si:Al 7.42 8.79
SiB:Al 7.81 9.19
EXPAN 335.43 320.74
Two Recipes: FILED AS - CR#2A CR#4
IN ORDER OF C.O.E LREV CF LREV CG
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D
STRONTIUM CARBONATE. 17.56 8.78% 3.45 1.72%
SILICA.............. 64.07 32.04% 63.20 31.60%
G-200 FELDSPAR G200. 31.86 15.93%
CADYCAL............. 12.60 6.30% 8.14 4.07%
DOLOMITE............ 23.90 11.95%
TILE #6 KAOLIN...... 50.01 25.00%
WOLLASTONITE........ 29.29 14.65%
F12 (FERRO3134)..... 22.78 11.39%
TALC................ 6.51 3.25%
EPK KAOLIN.......... 55.25 27.62%
MAGNESIUM CARBONATE. 11.39 5.70%
=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=
=3D=3D
200.00 200.00
CaO 0.42* 6.73% 0.57* 10.83%
MnO2 0.00 0.01%
MgO 0.27* 3.03% 0.32* 4.37%
K2O 0.03* 0.69% 0.00* 0.13%
Na2O 0.04* 0.71% 0.06* 1.36%
Fe2O3 0.00 0.20% 0.00 0.25%
TIO2 0.02 0.42% 0.00 0.09%
B2O3 0.17 3.41% 0.21 4.99%
AL2O3 0.49 14.05% 0.34 11.74%
SiO2 3.75 63.55% 3.20 64.88%
P2O5 0.00 0.09% 0.00 0.03%
SrO 0.24* 7.11% 0.04* 1.33%
COST/KG 2.28 1.88
Si:Al 7.69 9.40
SiB:Al 8.05 10.02
EXPAN 312.10 295.76
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