George Mackie on wed 26 nov 97
That makes four of us now who have had the same problem ( Louis,
Cathie,Terri, me). Glazes containing both lithium and borate produce
hexagonal crystals. Some of you clever fellows out there, Ron Roy,
whoever, tell us whats going on please. george
On Tue, 25 Nov 1997, Louis Katz wrote:
> ----------------------------Original message----------------------------
> My one experience with this particular problem (glazes with crystals
> precipitating out, where the glaze contains Lithium Carbonate and Gertsley
> Borate) was just last spring. I seived a raku glaze and threw out scads
> of crystals and decided to fire it anyways. Should have known by the color
> that the firing was up around cone ten. Didn't know until I saw the color
> of the foot of the pot.
> Perhaps we are creating Lithium Metaborate or Lithium Tetraborate? Perhaps
> one of the less ionically challenged can help us.
> On a similar subject a student mixed a glaze calling for boric acid and
> soda ash and ended up poping the lidoff her container from the escaping
> carbon dioxide. Not all of our chemicals are inert.
> Louis
>
Louis Katz on wed 26 nov 97
=3C/NOFILL=3E
------------------
Met a Chemist in the cafeteria line today=3B meatloaf, overcooked veges
etc. this kind of stuff is better down here than it would be in
Michigan, but ...
Anyhow says he =22 Yup the lithium will replace the calcium=22. He also
agreed that the Epsom salts would delay the problem for a time. He
also said that the lithium borate crystals are often used in
demonstrations because they are so good looking.
I didn't get any detailed information because he was a take out and I
was eating in.
Got the Soda kiln and large reduction kiln going. Hopefully they will
be red in the morn. Shuteye time.
Louis
Ron Roy on thu 27 nov 97
Hi George - you sure know how to get my attention - however reports of my
cleverness have been largely exaggerated.
I suspect it's mainly the lithium - it is slightly soluble and obviously
has an affinity for something dissolving out of the GB. Keeping the glaze
warm might help. I suggest taking some and slowly heating it and find out
what temperature the crystals dissolve.
Lithium Carbonate is not one of my favorite materials. The solubility means
it goes into the bisque when wet glaze is applied and some of it stays in
the body - it's a strange actor and can form layers of unequal
expansion/contraction within the body and the glaze. Not to mention what it
can do to the glaze in the bucket. Keep it to a minimum is the best
strategy - or use another source such as Petalite or Spodumene.
>----------------------------Original message----------------------------
>That makes four of us now who have had the same problem ( Louis,
>Cathie,Terri, me). Glazes containing both lithium and borate produce
>hexagonal crystals. Some of you clever fellows out there, Ron Roy,
>whoever, tell us whats going on please. george
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
Fay & Ralph Loewenthal on fri 28 nov 97
Ron in what proportion does one replace Lithium
Carbonate with Petalite or Spodumene? TIA Ralph in PE
SA where it should be middle of summer and it feels like
winter!
Ron Roy on sat 29 nov 97
>----------------------------Original message----------------------------
>Ron in what proportion does one replace Lithium
>Carbonate with Petalite or Spodumene?
Hi Ralph,
This is a job for calculation - It's a perfect illustration of why glaze
calculation is so important to the potter. You can draw what ever
conclusions you want from my example but keep in mind - this is not a real
glaze - I just made it up - It should be a durable glaze at cone 10 - all
the requirements are met when I compare it to the limit formulas I use.
You might conclude from my example that you need to replace every 1% of
lithium carb. with 9.375 of Petalite - but as you can see - Petalite brings
it's own SiO2, Al2O3 and some KNaO so there are other adjustments
necessary. NOTE - there is a LOT less clay in the second recipe - I would
suggest adding 1% bentonite to help keep it suspended in the bucket.
If you asked me to do it with Spodumene I would ask you - which one? I have
analysis for 3 different kinds and they are all different to a degree. When
I do fusion tests they look wildly different.
But the way - I don't have a sample of the Ausi Spod yet - Any generous
souls out there who would care to send me a couple of pounds?
Anyone trying this calculation with their program will probably notice some
differences - I spend a lot of time getting accurate analysis - but even if
I didn't it would be normal to see those differences because every author
uses different analysis. Remember - because we don't use different analysis
for each batch of materials we get - we commonly use "typical" analysis -
an average over many batches - Works fine with relatively stable materials
- the pits when you use wildly variable materials. The trick is to know the
difference and swing you glazes in the right direction.
Anyone who tries these - I would appreciate some feed back on how they look
and if they are similar looking.
RR's C 10 proposed glaze with Lithium Carb
-----------------
G 200 SPAR.......... 40.00 40.00%
WHITING............. 10.00 10.00%
TALC................ 10.00 10.00%
LITH CARB........... 2.00 2.00%
EPK................. 15.00 15.00%
SILICA.............. 23.00 23.00%
----------
100.00
FORMULA & ANALYSIS
------------------
CaO........ .12 7.31%
MnO2....... .00 .02%
Li2O....... .03 .88%
MgO........ .08 3.32%
K2O........ .05 4.73%
Na2O....... .02 1.36%
Fe2O3...... .00 .20%
TIO2....... .00 .05%
AL2O3...... .13 14.25%
SiO2....... 1.04 67.87%
P2O5....... .00 .02%
COST/KG 1.31
RATIO 8.10
EXPAN 438.24
WEIGHT 91.57
RR's C 10 proposed glaze with Petalite. (add 1% bentonite?)
-----------------
G 200 SPAR.......... 41.25 41.25%
WHITING............. 10.25 10.25%
TALC................ 10.25 10.25%
EPK................. 6.75 6.75%
SILICA.............. 12.75 12.75%
PETALITE............ 18.75 18.75%
----------
100.00
FORMULA & ANALYSIS
------------------
CaO........ .12 7.31%
MnO2....... .00 .02%
Li2O....... .03 .86%
MgO........ .08 3.32%
K2O........ .05 4.78%
Na2O....... .02 1.41%
Fe2O3...... .00 .12%
TIO2....... .00 .02%
AL2O3...... .13 14.35%
SiO2....... 1.06 67.79%
P2O5....... .00 .01%
COST/KG 1.47
RATIO 8.03
EXPAN 441.34
WEIGHT 93.71
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
Ron Roy on sun 30 nov 97
Re my reply to this - I left out some important fit comments about the two
theoretical glazes I posted as examples.
You will notice the expansion for both glazes is around 440.0 on the scale
I use. For most situations I try to keep the glazes I work on around 450.0
- this works for many bodies however - If you are firing to cone 10 and are
using a body that may be generating cristobalite you better be aware - this
expansion is too low and will lead to significant fit problems.
I have also noticed - spodumene - the Canadian (Tanko) or Ausi kind looks
like a better material to get lithium from simply because they have more
Li20 than Petalite.
Those of you who are working at cone 6 will soon realize - using a feldspar
like material to replace lithium is going to reduce the amount of raw clay
in your glaze - this presents a problem - keeping the glaze in suspension -
perhaps the solution is in replacing only part of the Lithium Carb with
Spod and adding some bentonite.
I suspect the lithium is in the glaze in the first place simply because it
is easy to add to a glaze to get more melt - a favorite technique for those
who don't know what else to do.
>----------------------------Original message----------------------------
>Ron in what proportion does one replace Lithium
>Carbonate with Petalite or Spodumene? TIA Ralph in PE
>SA where it should be middle of summer and it feels like
>winter!
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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