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mixing up test glazes

updated wed 26 oct 05

 

Grenard, Nancy C. on mon 24 oct 05


I'm about ready to mix up my first glazes --- ever!

I have chosen one basic recipe -- with 5 different colorants -- to make
5 glazes.

It seems to me that I should make each recipe separately rather than
stirring up *all* the base glaze and then dividing it into 5ths and
adding colorant to each 5th. Any comments or suggestions??

Also, how much should I make of each?

Thanks so much for any assistance you can provide.

Nancy C. Grenard
Persimmon Pots (in northwest central Indiana where the persimmon crop
is good!)

Paul Lewing on mon 24 oct 05


on 10/24/05 6:06 AM, Grenard, Nancy C. at ngrenard@PURDUE.EDU wrote:

> It seems to me that I should make each recipe separately rather than
> stirring up *all* the base glaze and then dividing it into 5ths and
> adding colorant to each 5th. Any comments or suggestions??
>
> Also, how much should I make of each?

Nancy, it seems you're getting a pretty good summary of different people's
methods, and they seem to be quite different. If I were making this series
of tests, I'd make a 500 gram batch of the base glaze, as I usually make 100
g tests batches. Then I'd add the water to the proper consistency and
divide the wet batch into 5 parts. This is easy if you use identical clear
cups- just get the same level in all of them. Then I'd add the colorants to
each batch. This way you know the materials are all completely blended. If
you weigh each 100 g batch separately, you run the risk of their being
slightly different. That's usually not enough to make a difference, but it
could be. I also don't screen my glaze tests- that wastes too much glaze.
I just zap them in a blender to break up the lumps.
However you decide to do it, congratulations on the beginning of your glaze
testing career. It's the only way you'll ever get glazes you're completely
happy with. And remember that the first one is just as likely to be a
"keeper" as the 10,000th one.
Paul Lewing, Seattle

Bruce Girrell on mon 24 oct 05


Nancy Grenard wrote:

>It seems to me that I should make each recipe separately
>rather than stirring up *all* the base glaze and then
>dividing it into 5ths and adding colorant to each 5th.

I would do it the other way. I feel that there is too much chance for error
if the ingredients are measured separately. You also spend more time
weighing. If you have a base glaze containing five ingredients, then to
measure out the five individual batches requires 5 x 5 or 25 weighings. If
you mix it all together you need five weighings for the large batch plus
five weighings to separate out the individual batches, for a total of ten
weighings. I just did this on a biaxial blend of 35 glazes where the recipe
had 6 ingredients. Doing it individually would have required 6 x 35, or 210
individual weighings, whereas doing it as a batch required 6 + 35, or 41
weighings. Big difference.

Each weighing is a potential source of error. In addition, when weighing
small quantities, you must weigh much more accurately, as any error affects
only that one sample. When weighing the entire batch, any error is split
evenly among the individual tests.

Mix slightly more than what you need, as some will inevitably be lost in
screening. In my biaxial blend, I decided that I wanted 100 gram tests, so
theoretically I needed to mix up a single 3500 gram batch. To account for
some losses, I would bump that to 3600 grams.

Once you weigh the main batch, mix it well. I won't get into a discussion of
dry mixing vs. wet mixing. If you wet mix, put in enough water so that the
mixture is easily screened, but still a little on the thick side. After
mixing and screening, adjust the volume to some convenient amount by adding
water (that's why you leave the glaze a little on the thick side). Now you
can measure out your individual tests by volume. Keep the glaze well stirred
during the volumetric measuring. Dry mixing will be more accurate, but then
you have to deal with dry screening, which is a pain in the butt.

Good luck

Bruce Girrell in leafy northern Michigan
itching to open the kiln door and find out if all that weighing was worth
it.

marianne kuiper milks on mon 24 oct 05


Hi Nancy,

I did that and recommend that you don't re-invent my
wheel! You never know how the base settles - which
chemicals are heavier than others. Therefore you will
not have an accurate (certainly for test glazes!)
result of true colors.

I would make the recipe smaller, if you can, then do
it five times. If not, do a cross-color test with the
remainder. You make a series of tiles or thumb-pots
(which is what I do).

If you would like to know what I learned from William
Tersteeg - great system) I will email it to you
immediately.

Whatever you do: tell me the results, ok?

Marianne

--- "Grenard, Nancy C." wrote:

> I'm about ready to mix up my first glazes --- ever!
>
> I have chosen one basic recipe -- with 5 different
> colorants -- to make
> 5 glazes.
>
> It seems to me that I should make each recipe
> separately rather than
> stirring up *all* the base glaze and then dividing
> it into 5ths and
> adding colorant to each 5th. Any comments or
> suggestions??
>
> Also, how much should I make of each?
>
> Thanks so much for any assistance you can provide.
>
> Nancy C. Grenard
> Persimmon Pots (in northwest central Indiana where
> the persimmon crop
> is good!)
>
>
______________________________________________________________________________
> 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.
>





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Rudy Tucker on tue 25 oct 05


Nancy,

I assume here that you want to mix a small amount of glaze to use on test
"tiles" rather than enough of each to glaze say five or six small pots. With
a little more effort you can expand your experiment to yield sixteen glazes.

If you want to end with 100g of glaze to use on your tile:

1) Thoroughly dry mix 1600g of your base glaze. I would blend and then
screen
at least five times.

2) Measure out five 300g batches, label (I use A, B, C ect), and add
colorant to each. Thoroughly dry mix. Now you have five glazes with a single
colorant and the base glaze to test.

3) Label ten cups with the combinations that can be made with A, B, C, D and
E. That is AB, AC, AD, AE, BC, BD, BE, CD, CE and DE. Mix 50g of A with 50g
of B, 50g of A with 50g of C, ect, ect. Now you have ten more glazes with
two colorants each to test. Your A, B, C, D, E batches may be slightly less
than 100g due to loss in all of the measuring and blending. But no matter,
the proper percentage of colorant will be there.

4) Mix each of these sixteen samples with water and glaze away.

Things to remember:

1) Label carefully and keep accurate notes

2) Be sure to thoroughly blend, screening helps break even very small clumps
of material down and disperse them evenly

3) Use all due safety precautions especially when dry mixing your glaze
materials

4) Your combined glazes ( ie: AB, AC, AD ect) will contain one half of the
colorant in A, B, C, ect. If you want the A in "AB" to represent the same
percentage as in "A", you will need to increase your original batch amount
by 500g. That way you will have sufficient base to mix 50g with each of A,
B, C, D. and E. If you do this, you need to double the amount of colorant
that you begin with in A, B, C, D. and E because itwill be diluted by 50%
when mixed with the base glaze.

Hope this isn't too concise to be confusing.

Rudy

David Gallagher on tue 25 oct 05


Nancy,
I would make 100-200 gram batches of the base glaze and then just add the colorants. I supposed its a question of how big your test tiles/pots are? I like to have a decent amount of glaze do I can dip it. I like to dip once one side and twice on the other. One other thing, instead of 5 different colorants I would pick a color your going for and then adding that colorant in 5 different percentages some where between 1-10 % (unless your using a very strong colorant like colbalt in which case much less is needed). If you do five different colorants, you have the potential of getting five crappy glazes... 5 variations of one colorant increases your chances of getting at least one you like. The only other suggestion I have is to use a consistant measured amount of water, that way you know that thickness is not an variable. Good luck, Im in the middle of my own tests as well, its a wonderfull experience.
David

"Grenard, Nancy C." wrote:
I'm about ready to mix up my first glazes --- ever!

I have chosen one basic recipe -- with 5 different colorants -- to make
5 glazes.

It seems to me that I should make each recipe separately rather than
stirring up *all* the base glaze and then dividing it into 5ths and
adding colorant to each 5th. Any comments or suggestions??

Also, how much should I make of each?

Thanks so much for any assistance you can provide.

Nancy C. Grenard
Persimmon Pots (in northwest central Indiana where the persimmon crop
is good!)

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You may look at the archives for the list or change your subscription
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William & Susan Schran User on tue 25 oct 05


On 10/24/05 9:06 AM, "Grenard, Nancy C." wrote:

> It seems to me that I should make each recipe separately rather than
> stirring up *all* the base glaze and then dividing it into 5ths and
> adding colorant to each 5th. Any comments or suggestions??

You can make the tests either way, weigh out the base 5 times, or weigh out
a larger batch of the base and divide into 5 smaller batches.

5 smaller amounts (100 grams each), each weighed separately might be more
accurate, than weighing 500 gram batch and dividing into 5, 100 gram
batches.
With a larger batch, you will need to dry sieve 2-3 times to totally mix all
the materials, thus losing a small quantity, leaving you with less than the
original 500 grams.
Minimum I would suggest is 100 gram amounts. Add this to about 1/4 cup water
as a starting point.


--
William "Bill" Schran
Fredericksburg, Virginia

Gary Harvey on tue 25 oct 05


If you will check the archives you will find a few discussions and
disagreements on this subject. Personally I mix up about 1000 grams of base
mix and add colorant to 100 gram test. I put in a Tupperware bowl, seal it
and shake for a long time. Some will not agree with this method. I also
don't use test tiles as others. I have found that very small bowls are
best for me. I use a black glaze pencil to mark the bowls. But I have read
about making a bowl shape and cutting it towards the middle to make stand up
tiles. I have personally made a slab and cut 1 inch wide to 5 inches
stripes out of the slab, then folded the ends up. They look like a "L" but
sideways. Now warning: Please be wise. Get yourself a good respirator with
at least a p100 rating. Not a face mask like the ones for dusk. You can
get one at the local paint store or hardware store. They have two filters on
them. Trinity Ceramics in Dallas also handles them. Because some of the
ingredients of glazes contain dangerous silica dust. Also some of the
colorants are toxic. So don't drink liquids when you are mixing the
ingredients. Also anything you use making glazes must never be used for
anything else ever! I hope this helps. From one newbee to another. Gary
Harvey
----- Original Message -----
From: "Grenard, Nancy C."
To:
Sent: Monday, October 24, 2005 8:06 AM
Subject: Mixing up Test Glazes


I'm about ready to mix up my first glazes --- ever!

I have chosen one basic recipe -- with 5 different colorants -- to make
5 glazes.

It seems to me that I should make each recipe separately rather than
stirring up *all* the base glaze and then dividing it into 5ths and
adding colorant to each 5th. Any comments or suggestions??

Also, how much should I make of each?

Thanks so much for any assistance you can provide.

Nancy C. Grenard
Persimmon Pots (in northwest central Indiana where the persimmon crop
is good!)

______________________________________________________________________________
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.