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Flocculation = Suspension ?

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I often hear people say that they use bentonite or some other material so as to keep glaze ingredients "suspended" and to prevent "hard-panning".  My question:

Are the terms "flocculated" and "suspended" essentially synonyms in this context?  For instance, if all of the ingredients in my glaze are well "suspended" is the glazeit then also well "flocculated"?  Or is there some essential difference or distinction between these 2 terms. 

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Flocculation or deflocculation refers to the ionic charge between the suspended particles that either allows them to easily stay suspended in a lot of liquid (flocculation) , or flow readily when in little liquid (deflocculated).  Bentonite helps this because of it’s particle size and shape, not because it’s dissolving in liquid and changing ionic charges the way sodium silicate or Epsom salts do.

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On 5/28/2021 at 4:32 PM, neilestrick said:

We put bentonite in a glaze because it suspends well, then we flocculate the glaze to get the other ingredients (that don't suspend well) to stick to it.

So .... not to belabor it but -- if all the glaze ingredients (the clay, bentonite, and all the rest) are indeed suspended and staying suspended it would by definition be "flocculated".   Right?

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So glad you asked this question, I've been fuzzy on this concept for a long time! Let's see if I'm any closer: 


A glaze has a certain state of liquidity based on what's in it and the amount of water.
If you don't like what it's doing, you can change it by: 

Adding a deflocculate (like sodium silicate).

  • What will that do? This will make it runnier/more liquid than one would expect based on the amount of water involved.
  • Why might you do this?  If the glaze is well suspended, but it's too thick to apply via dipping or pouring and adding water would leave too thin an application.

Adding a flocculate (like epsom salts).

  • What will that do? This will make it thicker than one would expect based on the amount of water involved.
  • Why might you do this? If your glaze is not well suspended, adding a flocculate could aid in evenly distributing the materials. 
    if your glaze is suspended well but you added too much water you could try this, but you'd probably be better off just letting some of the water evaporate.


Do I finally have the right end of the stick here? 

Edited by kristinanoel
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Seems to me you do!  I intend to go forth with this simplifying thought in my head:

Functionally, a well-suspended glaze is a flocculated glaze, and a flocculated glaze is a well-suspended glaze.

(Even though, as neilestrick points out above, its technically not "flocculated" unless the  suspension has been achieved by the addition of a flocculent.)

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@Rick Wise @neilestrick

the IUPAC (International Union of Pure and Applied Chemistry) has the "official" meaning of the terms "flocculation" and "deflocculation"

https://doi.org/10.1351/goldbook.A00182  flocculation   
https://doi.org/10.1351/goldbook.D01555  deflocculation   
the document for the official definitions of the terms. see pages 1820 & 1824 

logic also implies that something can't be deflocculated until it has been flocculated and vice versa. :unsure::)


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@kristinanoel Yep! That’s a good working understanding for ceramic purposes.

We run up against confusion with the scientific definitions because our ideal conditions lie in a spot where the chemical reaction isn’t exhausted. That’s why you have to use a light hand with either darvan or Epsom salts, because too much of either will do something undesirable. But it’s handy info if you need to siphon the water off your waste glaze bucket. Just overload it with epsom salt solution, and the slop will sink to the bottom of the bucket in just a few minutes.

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