Suspension Of Fritted Materials?

[Marcia Selsor]

After the thread on deflocculating and flocculating clays, I have a question regarding fritted materials that include mason stains, ferro frits etc. 

Artists have referred to adding epsom salts to a majolica mixed glaze to suspend the fritted material which is heavier than the more natural materials. Dick, Glazenerd, can you provide an explanation as to what is happening in the glaze below when epsom salts is added to this already mixed recipe?

 

Thanks,

Marcia

 

 

 

Majolica White Glaze Cone 03 Cone 05 Frit 3124 65.75 58 F-4 feldspar 17.24 20 EPK 10.82 2 Nepheline Syenite 6.24 7 Tin oxide 5 5 Zircopax 10 10 Bentonite 2 2

 

[glazenerd]

Complicated? But will do my best to make it user friendly.

 

Epson salts has magnesium ions, not oxides. Magnesium stearate ( stearin acid is used to break the molecular magnesium bonds) creates a chemical reaction ( ionic polarization) that acts like a suspension agent. However, that is a short lived reaction which is okay in short term use.

 

Any high frit, high magnesium, or high sodium glaze is subject to hydrophobic reactions: which dries and flakes almost as soon as it is applied to a bisq piece. This is where epson salts compounds the problem because of its magnesium ions. To truly suspend a high magnesium, frit or sodium glaze you need either a gum, calcium bentonite, or tartaric acid.

 

Then there is the cheap way . Mix one third Elmer's glue with two thirds water and apply. It will suspend, impede the cracking issue, and being organic: burn off completely.

 

Nerd

[Mark C.]

another note on suspending heavy materials-things like Frits or other heavy materials

epson salts do work but only with limited results.

I have a few heavy settling glazes that are beyond epson salts to carry the materials and I recommend Magama

its sold in a few places -hers one

http://www.bigceramicstore.com/magma-300-gram-bag.html

I have yet to find a better product for real heavy glaze materials-you must follow the directions of use as well for good results.

I use epsom in one glaze but I have few that it will not carry the load-magma is the solution

[Dick White]

Whut Nerd said. He's the chemist, I'm just a recovering accountant still trying to keep the debits and credits balanced in my glazes. In accounting, we do have a special additive (adapted from my earlier training in physics) called Finaglian's Constant, which when added to any wrong answer, miraculously brings it all back into balance. And so I will add some Elmer's glue to that. Thanks Nerd, never heard that trick before.

But not to move the conversation in a different direction... Nerd, what would you advise regarding using this glue trick in a thick crystalline glaze application as a substitute for the more typical CMC?

[glazenerd]

Well Dick, necessity is the mother of invention.

 

As you know, crystalline glaze is flakier than granny's biscuits. Early in my crystalline journey, after watching my glaze flake off a few hundred tiles, and after using every known suspender available: I eyed my bottle of Elmer's carpenters glue sitting on the shelf.

 

Chemical theory: x(2) y Mg4/SiO4 = "why the hell not."

 

Have actually used up to 50% in water: which by the way- elmers and straight alumina makes an excellent putty to bond pieces to glaze catchers. The elemers burns off, and the pieces pop off the catchers with little effort.

 

Now I use "Nerds Glaze Suspender" a combination of 11 herbs and spices.

 

Tom

[Dick White]

Ok, off to the races with that idea in my next batch. As if it isn't enough to be tweaking the % of the ingredients in the glaze each time... And for the risers, I am a card-carrying member of the EPK/Al/sawdust biscuit cabal, which I glue on with a thick mix of Elmer's and EPK (cheaper than Al hydrate). Pops right off after the firing.

[neilestrick]

Some of my glazes use a lot of frits. As long as the koalin is above 10%, plus 2% bentonite, the epsom salts work well. You've got to give the frit something to stick to that suspends well, so if there's not enough kaolin it doesn't work as well.

[Marcia Selsor]

have been using epsom salts to spend mason stains in porcelain slip..and epsom salts to suspend frits in majolica while dipping tiles into the glaze. I used gum tragacanth following herbert Sander's directions for crystalline glaze suspension back in the 1970s. Did my thesis on them. 

My bigger questions would be is the epsom salts acting as a flocculent or deflocculent when suspending frits in a glaze??

[Marcia Selsor]

Callie,

I got that much  .

Thanks. I understand that for a short while the epsom salts will suspend the heavier materials by  temporary deflocculation ignoring the classification as a flocculant over a long period..see Glaze Nerds explanation when I asked him if epsom salts was acting as a deflocculant when it suspends heavy fritted ingredients.

The sodium silicate will turn slip to gel if anyone is interested in decorating with embossed texture.

Marcia

[glazenerd]

Yes, it would be classified as such in the pottery world. Although chemistry wise; it is ionic reaction, in lieu of typical flocculation that is defined as colloidials.

 

Best comparison and easiest to understand is sodium silicate: it thins slip for a period of time, then begins reversing back to its original thicker state. Epson salts thickens a glaze slurry for a period of time, then begins to reverse that reaction. Coagulation would be the better term, but that would only cause confusion. So it is just easier to say- flocculation.

[Marcia Selsor]

Thank you Glaze nerd. I was baffled by this because I have been using epsom salts as a deflocculent for however short period of time it lasts, as directed by masters in the field of majolica. So here is a good example of practical application as compared to scientific definition.

I appreciate your explanation. Things are never as simple as they seem, nor are there hard definitions where so many variables are potentially changing things.

 

Marcia

[terrim8]

Thanks Nerd for the coagulation comment. Much better description.

[glazenerd]

Coagulation / agglomeration, and coalescence are the more accurate terms for glaze. Flocculation and deflocculation are from the soil sciences primarily. I assume those terms entered the pottery world because we deal with clay. Over the course of time, I also assume they got applied to anything that thins or thickens.

 

Other myths:

 

Talc is not a clay, neither is bentonite. ( both are minerals) just in the last few years have they been reassigned " mineral clay."

[Marcia Selsor]

I appreciate your scientific approach and also appreciate the clarification between science and pottery applications. 

Marcia

[glazenerd]

Marcia:

A forum friend, was friend enough to tell me that my posts were filled with too much technobabble. So I have been attempting recently to make them more user friendly. I realize the chemistry has little to no relevance to everyday pottery, but it is the way I process the information. However, even though it is just clay and glaze to most: there is still chemistry at the heart of it.

Tom

[oldlady]

your passion for the correct in any subject shows.  sometimes it is difficult to remember that everyone else may not have had the benefit of learning the basics  you think of as the alphabet.  which means they have no frame of reference for the more detailed descriptions of your deep interest and understanding.  humanizing the technical is an art in itself.

 

that is why technical writers need good proofreading.  i worked with engineers many years ago and many of them could not write a complete sentence but certainly knew their stuff otherwise.

[Dick White]

Tom, what Marcia and OldLady said. Me too, thanks for a lot of my learning from you.

 

dw

[High Bridge Pottery]

aw, what's a good post without a few things to google after 

[glazenerd]

Ty for the kind words.

Spent most of the weekend working on mathematical equations for the various aspects of stoneware formulation. Now for the fun part: assembling massive cross reference charts... Oh joy!! Writing formula limits for porcelain was so much easier.

 

Nerd