Flocculation and specific gravity

[Mark C.]

I always weigh my glaze and get it how I like it than and an suspesion agent-always done it that way

Never done it the other w ay around.

How does it work?? any change?

[glazenerd]

12 minutes ago, Mark C. said:

I always weigh my glaze and get it how I like it than and an suspesion agent-always done it that way

Never done it the other w ay around.

How does it work?? any change?

Agree Mark. Only use 3 glazes per se: but if you can learn to suspend crystalline- the rest is a cake walk. I use a cylinder because of easy calculation: 1 ml of water = 1 gram. The glaze is measured on a scale in grams= so calculation of SG just becomes a ratio. I make my own suspender. 

[Sorcery]

2 hours ago, Bill Kielb said:

Hmm, yes, but probably 20 ml weighs 20.001 grams. Just likely not able to measure it.

 

Sorry. 

Meant 20ml weighs 28g.

But I probably typed that wrong too!lol

 

Sorce

[Bill Kielb]

4 hours ago, Mark C. said:

I always weigh my glaze and get it how I like it

I really favor glazes that perform well enough under a preferred sg. If I  need to adjust its viscosity from there I tend to get tired of a glaze that needs the extra attention. For dipping, I am lazy and don’t have any favorites that are that demanding.

[Mark C.]

I only have 3 glazes out of 15 that need to be measured and only one that is critical . That one is my rutile blue which I use the most and have made for me by the ton dry mixed. Since it can run like crazy and wipe out an entire load I always tune it up and recheck it now and again.

[Hulk]

I've tweaked each of my "keeper" glazes sg and most o'm thixotropy as well. Per Rick's (second) question, the thixotropy may change a bit after sitting, and, allow newly  mixed glaze to slake a while, else anticipate re-adjustment after some days.

Just on account o' curious what distinguishes rheology, viscosity, thixotropy (from Wikipedia, Google, and Epoxy Technology):

  Rheology is not a measure of viscosity but an area of physics focused on the study of a substance's change in flow characteristics under applied stress or force.

  Thixotropic Index is a ratio of a material’s viscosity at two different speeds, generally different by a factor of ten. This value is indicative of a material’s ability to hold its shape. A highly thixotropic material will drop in viscosity as agitation or shear stress is increased. Mayonnaise is a great example of this. It will hold its shape very well, but when a shear stress is applied the material will easily spread.

  Thixotropy is a time-dependent shear thinning property. Certain gels or fluids that are thick or viscous under static conditions will flow over time when shaken, agitated, shear-stressed, or otherwise stressed. They then take a fixed time to return to a more viscous state.

  The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.

I do like words, somewhat! My intent is is mostly sharing (what I just learned), not so much lecturing, 'k?

What a difference adjusting glazes for dipping can make, aye, that's the point (for me) - where the glaze stays mixed better, is more forgiving (slow) in terms of film thickness per unit time immersed, is less prone to pin holes and crawlin', and is much less prone to sheeting and dripping.

[Dick White]

'xactly what Tom just said: "What a difference adjusting glazes for dipping can make, aye, that's the point (for me) - where the glaze stays mixed better, is more forgiving (slow) in terms of film thickness per unit time immersed, is less prone to pin holes and crawlin', and is much less prone to sheeting and dripping." We can talk the talk of pottery science, but unless we pottery walk the walk of pottery science, things just don't work as well. And when folks have misinformation or missing information about how things work, it usually doesn't get better, but rather gets worse. Establish the correct SG first, then adjust flocculation or deflocculation.

[Crooked Lawyer Potter]

I think i recall reading that successful flocculation is possible only at or within some appropriate range of specific gravity. In other words, my problem getting my glaze to flocculate may be because it is at some inapproriate SG. Or did I dream that?

[Hulk]

Good question!

My (limited) take lines up with Mr Hansen's observation, that a runny glaze that has high SG - likely in an attempt to limit the runniness - will need to have the SG lowered afore adjusting the thixotropy.

[Crooked Lawyer Potter]

I need a checklist.  My glaze seems to have defloc’ed.

1. Epson salts did not cure.

2. Bentonite and then epson salts did not cure.

3. The SG is 1.46, its norm.

What else can i do?

[Babs]

Why are you saying deflocced?

Is it hard panning?

[Crooked Lawyer Potter]

No, its thin and milky. My “finger stuck in it” test is like 2% milk instead of cream. 

[Hulk]

One o' these days I'll submit to Question of the Week a general/open question about measurement, with some specific focus on thixotropy and clay&glaze dust. Not today though!

Ahem, CL Potter, may I share how I try for uniformity in glaze behaviour (ah'll assume yes)?

  First off, for each glaze I'm noting the SG in my notebook. So far, I'm finding my glazes behave well between 1.39 to 1.48 - some glazes work better on the wet/low end, some on the high/dry end. Any road, I'm trying to dial each glaze in to its "ideal" SG.

  Second, I'll check out how the glaze responds to stirring (credit to Mr Tony Hansen's articles and video clip* on thixotropy) - I'm looking for the entire mass to rotate with togetherness. Contrast how water stirs - there are currents of several speeds whirling about, and as the liquid slows down the several speeds shear against each other - and it spins for a very long time before coming to a grinding halt. I'm looking for my behaving glaze to complete about three turns after I stop stirring**, then stop all together, exhibiting a bit of bounce back when the glaze mass comes to a stop, stretches a bit, and returns (Tony Hansen demonstrates in his video clip).

A glaze that "gels" goes on better wet (lower SG), else it's rather difficult to avoid putting it on too thick.

What the "gel" does for us, well, whether pouring out from the inside, or withdrawing from a dip, the glaze runs off the piece, being liquid, but then stops - no continuing to run and drip. The difference is stupendous, unbelievable, outraageous, err, "nice" may suffice.

:|

I'm not seeing problems getting the glaze layer thick enough - a lower SG on a less porous clay body (like the black clay I was working with) requires a few more seconds, and/or a second dip.

Glaze that behaves like a nice liquid when moving, but then >snap< just stops, it's soo worth it, my opinion.
Staying stirred up better, and hard panning less, these are side benefits, my opinion #2.

 

Try mixing your glazes up well, then stir to a specific/repeatable speed, and compare the behaviours as the glazes revolve to a stop.

The finger test, not helping me. I'd go with test tiles fitted up with small squares of tape, maybe; dip to a timed interval, pull, shake, wait on drying, then pull the tape to check dried film thickness, if film thickness is at issue. The clay body is a big factor, my opinion (#3), in how the glaze sticks on. Even raw clay (I'm bisque firing tho') doesn't resemble a live finger. Doesn't the clay absorb moisture, hence, there's a layer of dryer glaze against the piece? If the point is to check how well it goes on in terms of dripping and running, I'll still go with a test tile over th' finger. Given, one who's been finger checking for some time likely gleans a wealth o' information - like, perhaps, how my Grandma made pie crust, where no sense measuring, for the ingredients change, noo, she could tell just by the feel, aye, perfect.

Ah'll be quiet now.

 

*How to Gel a Ceramic Glaze - YouTube
  less than 12k views (11,043) on this'n, hrrm, how is that possible? 

** Trying for uniformity, one must therefore endeavor to stir the same way each time, hence, I use the medium whisk and stir clockwise to match the beat of "Positive Vibration" mon.

 

[Callie Beller Diesel]

@Crooked Lawyer Potter Can you provide the recipe? I want to see if there are soluble ingredients and what the clay levels are like. Also, when you say you added Epsom salts, did you add them dry, or did you make a supersaturated solution and add it to your batch? With an SG of 1.46, it should be suspended properly.

[Crooked Lawyer Potter]

Callie

The glaze recipe is below:

VC Matte Base

Custer feldspar.  40

Whiting.  16

Silica.  16

EPK.   10

Frit 3124.   9

Talc.    9

(Zircopax at 10-14 for whiteness?)

The zircopax is a recent addition to get more “white”. 
I added the epson as a supersatuated mix

[Callie Beller Diesel]

Did you mix the glaze for about 4-5 minutes before trying to dip? If it’s not that, you could just need a little more epsom salt solution. There’s nothing in there that’s too weird. 10% epk is a little low, but with some added bentonite, that should be sufficient clay.

[Crooked Lawyer Potter]

Can it really be that 4 or 5 minutes of mixing is required!  I mix vigorously but not that long. 

[Min]

Just to clarify, your glaze isn't hard panning / settling out but is now "thinner" than you would like it to be, and at 1.46 SG you get a thick enough glaze layer. If that's the case and you have been unsuccessful with adding more saturated epsom salts solution then I would try something else.

Some glazes respond better to vinegar than epsom salts. I would suggest removing a cup or so of glaze from your bucket and stirring in a few drops of vinegar, give it a stir and see if that does the trick. Dip a test tile and see if you like how it goes on. If it works then go on to adjust the bucket of glaze. Over time you might need to add more vinegar if you find the glaze deflocculates. 

If that doesn't get the glaze as creamy thick as you would like (while maintaining the SG) you could give MAGMA a try. This product will work really well to both flocculate and increase the glaze thickness. Word of warning about it though, side effect it has is to slow down the drying time of the glaze so there is a balance between slurry thickness and dry time. Once Magma is added you won't need to add more, it doesn't loose its effectiveness overtime. Do add the 0.04% copper carb if it's going in a glaze without copper as it will spoil / rot if not used up quickly.

[Mark C.]

Carefull with Magma as a little goes a LOOOOg ways-it can float bricks if you add to much.

I mix it with hot water and the copper and keep in a sealed container for use later as well. It really like hot water to mix in and power mixing is best (this is where the blender shines)