Alisa og Claus Clausen on sun 18 feb 01
Dear Clayart,
The following is a list of practical methods for mixing and testing =
glaze reciepes. Hopefully, something on the list will save you avoidable =
errors and troubles and keep your testing clean and systematic. The =
results then will only be as good as the glaze and not poor because of =
inefficient glaze mixing methods. Everything is very simple, but it =
gives an outline of what to do and how to work methodically so that your =
tests done and into the kiln.
=20
First and most important, be sure you are mixing glazes in a well =
ventilated area and are wearing the right mask with a good fit. Wear =
clothes that you leave in the studio so you do not track in toxins into =
your living area. Read up on your materials and be educated about what =
you are handling. Always use the recommended safety precautions. There =
are toxins in mixing glazes and you need to be protected. Like Mel =
said, we are not baking "cookies"!
People sometimes have a fear to overcome before they start to mix =
glazes. They are worried about wasting materials and or are reluctant =
in general because they have never done this before, maybe have never =
seen anyone mix before, and do not know how to get started. They have a =
justifiable nervousness. However, just like anything else, jumping off =
the dock for the first time, you have to do it to overcome your fear. =
Doing will empower you and before long, mixing glazes will be second =
nature to everything else you do well already in your studio.
1.
Have your bisqued (green if you are testing once fired glazes) test =
tiles, bowls ready and have a lot of them. Be sure they are clean and =
free of dust and debris. There can never be too many, because you may =
try one receipe with different oxide additions or painted slips, or =
other variations. My test tiles and bowls usually have a portion of them =
textured so I can see if and how the glaze breaks.
2.
Collect a file of glazes that are of interest to you and write them in a =
consistent way in a ring binder or on index cards. You add and subtract =
receipes as they work for you and you will have a ledgible receipe to =
mix from. Avoid writing receipes in several different books and places, =
because by notating multiple copies of receipes, you could be =
unintentionally playing a game of "telephone" with your numbers. It is =
easy to make careless mistakes when copying down receipes. Write them =
down, double check accuracey from your source and keep them in a place =
where they will not get wet or lost. Write one receipe on each side of =
the paper, because while you are mixing, your eyes can easily jump =
between receipes and you can become unsure about what you are doing.
3.
When you decide which glazes you want to test, you need to make of list =
of the materials you need to purchase. Do not spend a lot of money on =
less than usual materials to begin with. I started with Frit, Feldspar, =
Whiting, Silica, Ball Clay, Bentonite, Zinc oxide, Dolomite, Nepheline =
Syenite, Kaolin, Talc and a variety of oxides such as Red Iron, Cobalt, =
Rutile, Tin and Copper carb.
I had 100-200 grams of each raw material and 50-100 grams of the =
colorants.
4. =20
Keep your materials in water safe buckets, bins, sealed.
In addition to raw materials, I bought a scale, stole any spoon I could =
from the kitchen (not to be used again in the kitchen), had a supply of =
plastic bowls, plastic mixing spoons, a stalk blender, a lot of one way =
cups, a big bucket for glaze test excess (delivered on Sundays to the =
toxic dump area or you can fire the waste), empty glass jars for the =
oxides, and paper and pen.
5. =20
Mixing Day.
This is mixing day, mixing for as many hours as it takes you. If you =
think you will require 1 hour to mix 10 100gr. batches, give yourself 2 =
hours. When you mix glazes, mix them finished before going on to any =
other tasks in the studio. Concentration is important.
6.
Have your materials and any accessories for mixing readily available and =
within reach. Widely scattered buckets, spoons still in the kitchen, =
scraps of paper, etc. make for unnecessary gymnastics and eventual =
mistakes in mixing .
7.
Make a chain of repetitive movements. I find that I can easier catch my =
oversights if I "feel" that I have skipped a step in scooping, weighing, =
dumping, setting aside.
Set cup near scale, have buckets clearly labeled and more or less all =
together.
Keep you receipes close by, but not in the spill zone.
Read through the entire receipe and be sure you have all the ingredients =
you need.
Be sure your scale is set to the tare weight with whatever container you =
are measuring your materials into to before dumping into the plastic =
cup.
8.
Start to measure out materials.
Measure the first material, dump it into the cup.
Hold on to your spoon or place it on your counter.. (I like plastic =
opposed to metal because the materials cling less). Do not leave it in =
the bucket because you will spend time and lose concentration looking =
for your measuring spoon.
Write down what ingredient you just measured.=20
Meaure next material, making sure your scale is set at zero again,
dump into cup, write it down.
Complete measuring out of dry ingredients.
Measure oxides last. Make sure to clean the measuring spoon from
oxide to oxide to avoid contamination, so that you get an accurate color =
in the small test batch. Finish dry mixing all the receipes you will =
test this session.
9,.
Add water, clear water. This can be done simply by adding a small =
amount of water and mixing and adding more water until you get the =
desired consistency. Or you can add the dry ingredients to a small =
amount of water, adding the dry ingredients inbetween mixing up the =
slurry. Be careful to add less water than more, because a glaze slurry =
can become too thin by a small amount of water. I use the knuckle test, =
but you can also use a hydrometer. As you get more experienced you can =
judge a particular glaze's "correct" consistency for that glaze and/or =
the effect you want from that glaze.
10.
Blend each cup with the stalk blender, rinsing the blender from cup to =
cup. Be sure to use cups with a bottom width wide enough to accommodate =
the blender head. I have been standing with 15 cups that were too =
narrow for the blender. As you blend up the cups, set them aside so they =
are not in danger of being knocked over by the blender cord or anything =
else. Best to let the cups stand over night to "soak" and you will =
most often get better fired results because the glaze slurry is well =
blended.
11.
You are ready to dip your test bowls or tiles. I dip all my glaze tests =
because that is how I will eventually apply the successful glazes. You =
can brush on the glazes if you work that way.
=20
For test bowls, I first pour the inside of the bowl, swirl it around and =
pour out excess back into glaze cup. Then I dip the test bowl into the =
glaze slurry with a good enough bare margin at the bottom to allow for =
dripping. Sometimes the glaze is just too fluid and will run off =
anyway. Then I let the bowl stand in front of a warm air blower until =
it is dry. I dip the rim and little way down a second time to see how =
the glaze will behave where thinner and thicker. I use bowls to see if =
the glaze will pool. Set the test aside.
Otherwise I use tiles with holes (that stand upright so I can see how =
stable the glaze is) in them for color tests. When I dip the tiles, I =
dip them, again, with a bare margin at the foot. Then I dip the top of =
the tile again. After firing, I tie the test tiles together into =
bunches, so I can readily see the progression and effect of increased =
percents, blended and various pure oxides in the same base.
12.
Make a thin solution of iron and water and get a thin paintbrush. Write =
the name of the glaze and any abbreviations you will understand later to =
identify the tile after firing.
13. =20
Stack your kiln, setting the glaze tests in any available empty space =
between your work for firing. Fire your kiln as you do.
14.
Unload your kiln and check the test results. Inspect them in daylight =
to best see the surface. Feel them and look at them several times. =
Write down your description of the glaze test (color, texture, surface, =
feel, stability, etc.) on the page in your book with the receipe. Write =
any notes about the glaze that you may want to alter in another test, =
i.e. placement in kiln, thickness of glaze, substitutions of materials.
15.=20
Keep your test results. They are interesting to look at over and over =
again and you may need one of the glazes at a later date, although it is =
not something you need at the present.
16.
Any glaze you think you want to mix up in a bigger batch, test again on =
a bigger surface then the test tile, but not an entire kiln load of your =
"good stuff". Good first tests are not always repeated for a multitude =
of reasons. Test the glaze on all the types of clay bodies you may want =
to use it on for a good fit. =20
17.
Dispose of your glaze waste responsibly.
Hope you have many successes.
1b.
FOR MIXING BIGGER BATCHES OF GLAZES:
Same safety precautions. The methods are the same, but as you mix more =
you will find your own patterns and rythyms, becoming more secure in =
your process. You will not need to double check over yourself as much as =
listed above. =20
2b.
When you have your 100 gram receipe, figure out how much you want to =
make, say 5000 grams (fills a 10 ltr. bucket), and multiply out your =
measurements before you start mixing. If the receipe calls for 10 =
Silica, you will need 50 x 10 of Silica and so on for the rest of the =
materials.
3b.
When you have your dry mix in the bucket, cover it and shake it up, or =
mix it well with a utensil. I start out with a slightly short litre of =
water to every 1000 grams of=20
dry mix. Pour 3 short litres of water into a bucket. Gradually add =
some of the dry mix as you stir up the slurry with a gloved hand. Or =
add the mixture and mix the entire time with the stalk blender. Mix in =
the next litre of water, add rest of dry mix. Check consistency. Add =
rest of water as needed to give the slurry the consistency you want.
4b.
Have an empty bucket ready with a 60 or 80 mesh sieve securely fitted on =
top of the bucket. Pour the glaze slurry through the sieve slowly and =
either use a gloved hand or a kitchen brush to stir the slurry around in =
the sieve and down into the empty bucket. Empty the first bucket =
compelety for lumps, etc. Lift the sieve from the bucket and slide your =
hand or brush underneathe the sieve to release any glaze slurry hanging =
in the sieve. Blend up the glaze with the stalk mixer or a heavier one =
if you have it.
5b.
Repeat same process again, sieving back into the original bucket.
6b.
Your glaze should be tightly lidded and stored at preferably room =
temperature.
My studio is cold in the winter but not freezing. Every time you glaze, =
mix your glaze well up from the bottom. Some glazes need to be stirred =
frequently during glazing. If your glaze requires more water, make sure =
you mix the water well into the slurry before you do a consistency =
check, as not to be checking the consistency of the top water only.
I hope anyone who may read and who has additonal check points, =
corrections, pointers and/or ideas, will post them. =20
Mixing glazes from receipes is not mysterious. You some space and to =
concentrate. Mistakes happen anyway, but perhaps this list will be a =
jumping off point for those who are starting. Good luck. Altering, =
adjusting and developing receipes, that is the next step. Luckily we =
have Clayart.
Best regards,
Alisa in Denmark
=20
=20
ababi on mon 19 feb 01
>Dear Clayart,
>The following is a list of practical methods for mixing and testing >glaze
reciepes. Hopefully, something on the list will save you avoidable >errors and
troubles and keep your testing clean and systematic
An add: I use disposal cups for my
100 gram batches. We have a local, dairy and I
purchase through them a whole carton, kind of plastic of margarine\cheese.
I use lately tall - half liter cups (500CC) this way I can mix the glaze safely
without splashing all over, with a
hand blender or lately with appropriate Jiffy mixer that I cut to be shorter
in a way that it will not shake while I use it.
I use, a separate cup for cobalt, chrome or any other colorant, plus disposal
spoons.
After mixing the glaze I wash the mixer in water. I do not wash or use again
the cups with the colorant as the tests must be reliable.
Ababi Sharon
http://www.milkywayceramics.com/cgallery/asharon.htm
http://www.israelceramics.org/index.html
My ceramic works at:
www.photoisland.com
ID:sharon@shoval.org.il
PASSWORD:clay
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