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Glazes Behaving Badly In The Bucket

is defloculation my problem?

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#1 clay lover

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Posted 13 August 2013 - 02:37 PM

I have a loose understanding of the flocculation - defloculation issue, and have been doing well with my ^6 glazes for several years.  Lately, with a couple of buckets that have been around my studio for 3+ years, I have noticed issues that make me wonder if they need to be deflocculated some, rather than the usual flocculation process I use with most buckets. Do glazes change over time in this respect?

 

This is new to me and I would like some advice before I start tampering with them.  I have read several articles on this issue and done a web search for more info, but still...

 

They are from M^6Glazes, so are well balanced recipes.  Although they don't settle into a hard layer at the bottom of the bucket,( I am familiar with that degree of defloculation )   When dipped, the glaze runs and forms heavy drips on the ware, no matter how I rotate the piece while it drips.  I actually pop the glaze beads off after the glaze dries. The dipped pieces dry quickly except for the lower edge where they went into and out of the bucket and the final drips landed.  That takes longer to dry.

 

 The fired results looks thin. Do I need to use some Darvan in this glaze?  Are there  degrees of defloulation?  These glazes have a layer of about 2" of clear water on top, then a very fluffy. easily stirred  mixture that seems somewhat well dispersed down to the bottom of the bucket.  This is after sitting several days.  I thought a deflocculated glaze settled into a chewing gum like layer.

 

Can someone offer advice?  What about a thread that pinpoints symptoms of glazes that need one treatment or the other to behave well when dipping?

 

Thanks, All..

 

 



#2 neilestrick

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Posted 13 August 2013 - 03:28 PM

You do not want to deflocculate your glazes. It makes them thinner/watery and they will settle badly. Deflocculants are used in slips, not glazes. You want to flocculate the glaze with epsom salts, about 1/2% by dry weight- just dissolve 2-3 tablespoons of it in hot water and add it to your glaze. You will see an immediate thickening of the glaze, and it will not settle as badly.


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#3 clay lover

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Posted 13 August 2013 - 04:52 PM

Thanks, I realized I had switched the terms and had clicked on Edit' to correct it when the lightning boomed and all the power went off, so the post stayed uncorrected.  I meant to say, should I flocculate this glaze some?

 

Should I take off the standing water on the top of the bucket before I add the Epsom Salts?  Then add back as needed?

 

I watched the you tube by John Britt on this subject, and he talked about glazes that seem too thick, thixotropic,.  I have some like that also.  They look like sour crème, until I put the mixer in them, then they loosen up and mix and suspend well, but don't sheet off waxed bottoms and tend to go on too thick.  I had been thinning them with more water.  John Britt's video says to use Darvan in them.  He recommends adding a defloculant to that type of bucket of glaze.  There is 2"-3" of water standing on those buckets.  Should I remove the water before treating the rest with sodium silicate?



#4 neilestrick

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Posted 13 August 2013 - 08:00 PM

Personally, I would never us a deflocculant in a glaze. Just add water. The danger is that if you over-deflocculate it, it's very difficult to bring it back.


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#5 clay lover

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Posted 14 August 2013 - 07:27 AM

With the first case , the bucket that goes on thin, and makes heavy runs,  It is not over settled, it is soft and easily stirred up.  with only a little standing water.  I have put my hand down to the bottom of the bucket and it doesn't seem much thicker there than at the top.  Does it still need to be more floculated?  Removing the little bit of water would not make much difference, perhaps 2 cups on a 4 gallon mixture.

This is a glaze that performed well for a long time, then sat for a year.  Does the mix change with time? other than maybe drying out some?



#6 neilestrick

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Posted 14 August 2013 - 11:41 AM

Try removing some water first. If it's still not thick enough, add epsom salts. It will thicken nicely. Most mixes don't change other than drying a bit, but some, like Shino, can if they contain any water soluble ingredients.


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#7 clay lover

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Posted 17 August 2013 - 08:07 AM

The thin buckets,I looked at more closely.  There was a tough rim of glaze in the corners of the bottom of the bucket I had not noticed before, so I figured you were right on about it needing some defloculation.  I took the water off the top, then added about1/2 of a 1/4 tsp measure of epsome salts, stirred, waited a minute, then checked it, a bit better but still seemed thin, dipped a test tile, lots or runs and drips, so added the rest of the 1/4 tsp and looks better, this was a 4 gal. bucket of glaze, so not much added.

 

The thick bucket that  you said not to defloculate, I pulled a Qt. off added water and tested it, it still would not shed off the waxed bottom of a test piece, but left what seems like too thin a coating.  What would keep it from releasing off the waxed bottom?



#8 neilestrick

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Posted 17 August 2013 - 09:38 AM

A lot of glazes don't sheet off the wax very well. I find that glazes that are high in feldspar or clay or iron tend to cling more.

 

Make sure you're dissolving the epsom salts in water (hot) before adding it to the glaze.


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