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Chantay

Sieving Glaze Results

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I was mixing up some small amounts of glazes to test.  I used this recipe:

 

Honey #1

Spodumene     75

Flint                  50

Gerstley Borate 35

Talc                   32.5

Dolomite           17.5

EPK                  12.5

Rutile                 15.

 

I know it doesn't  add to 100.  Friend gave me the recipe  but I can't contact her to ask questions.  I know she used it frequently. 

 

My question is, after mixing I sieved using an 80 mesh screen.  About half of the Spodumen didn't pass through the screen.  Is this due to a defect of the spodumene?  I had let is sit for two days mixed up so it was well saturated.  I put the contents of the sieve back in the container for now.  Should I just use it unsieved?

 

 

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You have to force the mix through the sieve.  Use an old credit card to scrape the mix back and forth across the screen.  Force it thru the screen.  Always sieve a mix it breaks down the mix to the size of the screen, at least. This helps in distributing the components of the glaze throughout the entire glaze. No lumps here and there.

 

If you are making small test batches, don't sieve, use a submersible mixer.  Search for John Britt's videos.  He puts the glaze dry mix in a 16 ounce Solo cup, adds water then hits it with the submersible blender. I add about 3 ounces water to every 100 grams dry mix.

 

Hope I haven't misunderstood what you were asking.

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spodumene seems to be granular.  waiting for it to "slake" has never worked for me.  a grain of sand remains a grain of sand no matter how hard i try to get it to go through a 60 mesh screen.  yes,  a sixty mesh screen.  even after sitting for years it is still a grain of sand.  spodumene sand.

 

what do the experts do???

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either the spod clumped or or is too granular. If it is too granular there is nothing you can do about it short of re-grinding with a mortar and pestal, or going to a larger screen size. If it is clumped then you  may be able to force it through the screen as dhPotter said. I don't use a credit card. I use a stiff paint brush. I think this is easier on the screen than something rigid.

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Well, Hmm, I let the mixture sit for over 48 hours and it didn't seem to 'slack'.

 

I did try and use a credit card, and scrub brush to try and push the granular pieces through the screen.

 

I also used a submersible mixer.

 

I am wondering if I make sure the spodumene is evenly dispersed through the glaze if all will be OK during firing.  It will melt and not be noticeable?  I'm just surprised because only about 1/3 didn't go through the screen.  Next time I may prescreen the spodumene and use only what passes through.  Although this seems like an expensive idea.

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Be careful trying to force materials through sieve screens... if the screen gives before the particles, you'll ruin your sieve by widening some of the holes, making capable of passing particles larger than it's rated for.

 

I would never use the word "force" when talking about sieving materials.

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This happens to me with tin oxide, so after measuring out, I soak the tin in warm water for a couple days while the rest of the recipe is slaking. Then I get as much through the sieve as possible. My recipe seems good, so I assume I have extracted enough.

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Dry screen the spod as you weigh it out., that way most if not all will wet screen later in your final screen.

Wyndham

THIS.  There are a few materials that tend to be more clumpy and larger particle size than others - for me it's stuff like borax, cornwall, soda ash, etc.  Pre-screening the material you're weighing out helps tremendously.  keeping a simple mortar and pestle in your equipment inventory is also a very helpful tool in these situations.

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Titanium dioxide is my biggest headache. I always pre mix it separately and wet screen it into the glaze, then mix and screen again. One thing I have found that helps with clumpy materials, is dissolving them in just enough denatured alcohol to cover them, and then mixing. This serves as kind of a wetting agent and also helps cut down on mold in the mix.

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