Hudson River Clay

[GreyBird]

2 minutes ago, C.Banks said:

 

Your long-hand UMF work speaks for itself.

After I finished school I was done with plotting curves and defining limits so avoided long-hand work like the plague.

Yes, but you earned the right to do that by doing the hard work of learning first. That's where I'm at. I'm not ready to jump right into the software. I have to learn about everything first

[glazenerd]

Mary:

looking at your sheet, the math looks correct. You know and understand more than you give yourself credit for. Spent the day thinking about how to simplify this: a teacher I am not. 

The three columns RO, R2O3, and R2 are catergory types. RO are fluxes, R2O3 are metaloids, and R2 are glass formers .(silica primarily.) The easy way to study them is looking at the periodic table. The 2 left hand columns are alkali, which we call fluxes: lithium, potassium, sodium, calcium, magnesium, and strontium. (Barium is omitted because it is rarely used as a flux.) The middle section are transitional metals: copper, nickel, iron, zinc, cobalt,metc. The right column are metaloids: boron, alumina, and silica. I left some out intentionally: this is introduction 101, not masters degree. So I am limiting it to commonly used materials.

RO (fluxes) are found in the left hand columns.  R2O3  are easy to spot because of the (O3) ending. Alumina is Al2O3< see the O3 ending? Boron is B2O3, also an 03 ending. So if an element ends inO3, it goes in the R2O3 column. ( some over riding theories about what column boron belongs in.) R2 are glass formers, silica being the primary one in our trade. Starting out, I would only do recipes that use potassium, sodium, and calcium  in the RO column until you get your head around it. These three make up the vast majority of recipes. Same for R2O3, use just alumina for now. Use only silica in R2, it is the primary glass former used in the majority of glazes. As I said, there are others in each category, but there are also over riding application rules that complicate the basic application.

RO is suppose to add up to 1 (.03 + .07 = 1)  if you are watching Matt, he will explain it. So in easy terms: fluxes add up to 1 after you get this down, then cone range comes into play. At the lower cone 04/06, more fluxes, and lower temperature fluxes are used. (This is where boron gets confusing and moves from R2O3 to RO)  

R2O3 is just the simple math of total %  times atomic ( also called molecular) weight. This total then plays into formula limits. A minimum  and maximum %. 

R2 is the total glass formers ( silica). Same as  R2O3- total  recipe % times atomic weight equals? This total plays into formula limits as well: a minimum and maximum applies. 

The total R2 is divided by the total R2O3 equals the SiAl ratio.  EX. (Easy math) .40 silica divided by .10 alumina = 4/1 SiAl ratio.

actually doing it by hand will get it in your head, then you can use a calculator, after it makes sense.

leave out the strontium, barium, zinc, lead, boron for now: it will just confuse you at this point. Keep it simple, get your head around it, then add the rest,

additional info: a "mol" of a substance is a theoretical cube: similar to a sugar cube. A mol of silica is 60.09, which is its atomic weight. They leave off the 27 zeros that come after the 60.09 to make for easy math.

when looking at the periodic table: the elements on the left are the easiest to break apart; rather by heat or solvents. As you move across to right, they are harder to break apart. The ones on the right (noble gasses) are the hardest to break apart. Knowing that gives you some indication why fluxes are on the left, and silica and alumina to the far right. Metals are in the middle. 

So there is the simplest starting point I can come up with. 

After the formula comes learning the materials. Every natural mineral adds alumina, silica, fluxes, and metals is differing proportions: a calculator saves you the headache of keeping a running total.

TY for the condolences.  Tom

[glazenerd]

Mary:

This is the easiest periodic table to follow. The two blue columns on the left are alkali fluxes (RO) the middle red table are transitional metals: pottery uses the top row of this section primarily. The upper corner of the right (gold)section are the three primary elements used in pottery: alumina, silica, and boron. 

https://www.webelements.com

[Min]

Linda Bloomfield Simplified Periodic Table for Potters. If you expand the page the colour coding is explained in the lower left corner. 

  

 

[GreyBird]

Hi Tom, Thank You!  Todays lecture is all on Boron so that should be interesting. As for the above, Matt is using R2O & RO to represent The first two columns, Fluxes, Alkaline Metals and Alkaline Earths. And yes, the target ratio is 0.3 R2O to 0.7 RO. So Hudson River Clay having .48 Alkaline Metals and .517 is way off... Not sure how to fix that but working on it  I think I just need to add .94 more RO? So maybe Whiting? Again, Just adjusting to make it work as a stable glaze on it's own. Can tweak from there.

Thank you both for the Periodic Tables! This one came with the class and I like it because, Similarly to Mins, It shows Specific information for potters but I like the way it is laid out a little better than Mins because you don't have to look away from the element to know exactly what part it plays in the process (See Attached).

[GreyBird]

The Boron Lecture of course gave great info. But again, Not a whole lecture's worth. I don't really care about the history of the Gerstley Borate mine or boron used in underground nuclear testing because it absorbs radiation very well and he talked way too long about both of these things. The ceramic facts go by in a flash but he really likes to delve into he details of the sidetracks. I do applaud his enthusiasm!

Anyhow, the reason I'm here... I'm not sure of course, but I think adding some amount of Walostonite to the Hudson Valley Clay could fix both the Si/Al ratio and the Flux Ratio. I'll have to plug that into the chart and do the math and see where I end up but... I'm excited! and hopeful. Got to take a break and feed the birds... Raccoons... squirrels....chickens... stray cat. But then you know I'm getting right back to it! 

PS... We are under a Tornado watch here in Croton on Hudson, NY until 12am. Fairly unusual for around here. Quite exciting

[GreyBird]

OK Question for you all, Since the Stull chart says Molecules SiO2 and Molecules Al2O3 are we plotting moles on the chart or UMF Numbers or the original Formula % Numbers? or the Normalized % Numbers? I'm going to go back through the video lessons but I'm thinking it'll take me forever to find it. Might be quicker to ask here.

[Dick White]

The axes on the Stull chart are the molar UMF numbers for Si (X axis) and Al (Y axis) respectively.

[GreyBird]

Thank You... So important!

[glazenerd]

Mary:

calcium additions in the Hudson is incorrect. There is a touch over 5% now, coupled with the fact that clay is an >Aluminosilicate < that is highly refractory ( cone 32), that resists flow naturally. One of the reason I have been using spodumene in my Hudsonn trials is to supply some alumina, silica, and flux. Calcium stiffens a glaze, in this case the opposite is required.

gerstley borate is B2O3, which is known as a >sesquoxide>. Boron is a unique material because it can form glass on its own >borosilicate<.  To understand how boron works, you have to understand >Redox<  not really necessary information for potters, but it explains what happens in a kiln, and those effects on materials.  From your posts, you seem to be grasping it already.

t

[curt]

On ‎10‎/‎1‎/‎2018 at 10:01 PM, GreyBird said:

Too funny Curt... Here's the next topics in the class lectures. The Universe is right on track as usual ...

Hi Mary, too right!

 And as a side thought, isn't it great how your wild clay find is turning into a case study in clay and glaze chemistry in this thread?!  A breath of fresh area in an area where we are so frequently picking over well-travelled mainstream glaze recipes, or engaging in arid academic debates about glaze chemistry minutia! 

I have seen many "successful" glazes, including some I am using right now, that do not meet the  R2O:RO .3/.7 criteria.   In fact some are far from it.  The range of fluxes we have available as potters is considerable, and there are many different combinations outside of this magic ration which will "work." Each "successful" glaze has various strengths and weaknesses, many of which are able to be teased out using glaze chemistry (and software!) , but some of which depend on things beyond the glaze chemistry, eg, material particle sizes (possibly relevant with Hudson Clay as it is not a commercially processed material) .     As we say in the land down under, it is "horses for courses", meaning, in this case, which glaze chemistry is best depends a lot on the situation.  Just depends on your criteria of successful.  No doubt .3/.7 is the ideal flux ratio for some situations, but not all. 

What I am driving at is that I would not get too hung up on exactly meeting this .3/.7 ratio in practice.  If, for example, your glaze is only going to be used as decorative surface rather than on a functional surface,  there are a wide variety of alkaline and alkaline earth flux combinations that will "work".  "Taming" your wild clay by getting it to work in different situations is part of the fun!

As someone else said, see the Currie Tile Forums thread elsewhere here in the Glaze and Chemistry section for a practical way to explore the full range of possibilities with your found material.  If you go down that road I have no doubt that you will find many different glaze chemistries of interest.

[GreyBird]

So now that I have sufficiently played around on my own, I decided to revisit the insight software and low and behold... I can now glean some info. from it. For instance, if I am reading it right, it says my Si/Al ratio is 5/1 which is good. It also says that my R2O:RO is 0.3:0.7 That's not what I got but that's right on target. I'm sure there are you tube tutorials on the software.. I'll look for them. Maybe the software made and adjustment to correct the ratio? Or is my Hudson Valley Clay perfect to use as a semi Matt glaze, as is?  My UMF Numbers were all slightly different. For instance I had 57.72 Si and insight changed it to 59.08% in the Auto Unity Formula Analysis.

I can't wait, I'll fire up a tile tonight!!!

[GreyBird]

16 hours ago, curt said:

As someone else said, see the Currie Tile Forums thread elsewhere here in the Glaze and Chemistry section for a practical way to explore the full range of possibilities with your found material.  If you go down that road I have no doubt that you will find many different glaze chemistries of interest.

Curt, I am looking for this thread and not finding it. Can you give more info. or post a link here?

Muchas Gracias!

[Pieter Mostert]

16 hours ago, glazenerd said:

 Calcium stiffens a glaze, in this case the opposite is required.

That's not always the case. I've done several line blends (at cone 4) where I just added increasing amounts of Whiting to a glaze, resulting in an increase in fluidity, up to a point.  If you keep adding Whiting, sooner or later your glaze will become underfired, since Whiting on its own has a pretty high melting point.

What sticks out for me from the Insight analysis is the high UMF value of alumina. Have a look at the glazes plotted here (you can refine them to show only cone 6 if you like. I assume that's what you're firing to). There aren't many with Al2O3 as high as 0.99, and most of those that do, have high KNaO.  Adding Wollastonite will bring down the Al2O3 UMF value, in addition to increasing to Al2O3 : SiO2 ratio and getting the flux ratio closer to 0.3 : 0.7 (Insight rounds off the numbers). But it might be more informative to do a biaxial test where you add both Whiting and Silica. I've attached a test I did where I increased Silica going left to right, and increased Whiting going top to bottom.

I'm not claiming you'll get a stable glaze this way, since I think Matt recommends some boron for cone 6 glazes. But I also think the tests he did on stability didn't involve iron, so I'd be reluctant to  extrapolate from them. I should point out that I haven't taken his course, so I could be completely wrong about this.

[GreyBird]

Thank You Pieter,
Yes, I did write down .4 to .25 Boron for cone 04 & cone 6 if your fluxes are equal to 1 but my note taking is pretty weak so I'll revisit that lecture for sure. Thank You.

So what you are pointing out is that even though my ratios look good the Si/Al amount is just too high for the amount of fluxes I have? I had come to that conclusion too at one point and thought of using Wallostonite but hadn't gotten to the point where I figured the right amount yet. A

Actually the software works great for this too... although I'll still do the line blends at least I have a better Idea of what to use! This is awesome!

[glazenerd]

Pieter:

On October 1, 2018 at 4:41 AM, glazenerd said:

GM Mary:

from a quick glance, looks like you are analyzing just the Hudson? I mentioned earlier that the chemistry for melting this slip falls into the abyss: neither glaze or clay chemistry is wholly applicable. Typically the maximum clay % added to a recipe is 20%, and that is primarily done to boast alumina content and to control drying/flaking issues. In this scenario, clay accounts for 50-75% of the recipe: which brings in some parameters from clay chemistry. 

 

 

While I do not disagree per se, these Hudson recipes have 50-75% clay additions. Whiting additions in a glaze recipe and this clay have differing outcomes. Iron in this case is a major player in applicable chemistry. Mary had serious shivering issues in her original,posts, which I suspect iron is part of that. There are ways to deal with iron in clay chemistry.

Mary: yes, hudson has a nearly perfect "glaze chemistry", but alas it is clay.

In other news; I have not sent the Hudson porcelain yet because I am rather fascinated by its drying and hydration properties. It took 5 days for a sample to dry in 90 degree/low humidity conditions. I dried a 500 gram solid cube for hydration test. Putting the entire block in a plastic bag with  1/2 cup of water: it was mush the next morning. Both parameters are unheard of in the porcelain clay world. Most intriguing. I have been experimenting with chemical remedies to slow down the rapid drying properties of porcelain with limited success. I now have it figured out..(I think). Your clay also plugged a hole in my two year study or iron molarity and it's effect in clay. I have been trying to get my hands on magnetite based clay for some time: so again many thanks for the samples.

T

[GreyBird]

31 minutes ago, glazenerd said:

Pieter:

While I do not disagree per se, these Hudson recipes have 50-75% clay additions. Whiting additions in a glaze recipe and this clay have differing outcomes. Iron in this case is a major player in applicable chemistry. Mary had serious shivering issues in her original,posts, which I suspect iron is part of that. There are ways to deal with iron in clay chemistry.

Mary: yes, hudson has a nearly perfect "glaze chemistry", but alas it is clay.

In other news; I have not sent the Hudson porcelain yet because I am rather fascinated by its drying and hydration properties. It took 5 days for a sample to dry in 90 degree/low humidity conditions. I dried a 500 gram solid cube for hydration test. Putting the entire block in a plastic bag with  1/2 cup of water: it was mush the next morning. Both parameters are unheard of in the porcelain clay world. Most intriguing. I have been experimenting with chemical remedies to slow down the rapid drying properties of porcelain with limited success. I now have it figured out..(I think). Your clay also plugged a hole in my two year study or iron molarity and it's effect in clay. I have been trying to get my hands on magnetite based clay for some time: so again many thanks for the samples.

T

T, You are most, most welcome. I am so happy it is useful for you. I have a question... while it probably will make your porcelain more elastic won't it also pollute it with that nasty Iron? Isn't the point of using the Porcelain to have a nice clean white body?
M

[GreyBird]

3 hours ago, Pieter Mostert said:

That's not always the case. I've done several line blends (at cone 4) where I just added increasing amounts of Whiting to a glaze, resulting in an increase in fluidity, up to a point.  If you keep adding Whiting, sooner or later your glaze will become underfired, since Whiting on its own has a pretty high melting point.

What sticks out for me from the Insight analysis is the high UMF value of alumina. Have a look at the glazes plotted here (you can refine them to show only cone 6 if you like. I assume that's what you're firing to). There aren't many with Al2O3 as high as 0.99, and most of those that do, have high KNaO.  Adding Wollastonite will bring down the Al2O3 UMF value, in addition to increasing to Al2O3 : SiO2 ratio and getting the flux ratio closer to 0.3 : 0.7 (Insight rounds off the numbers). But it might be more informative to do a biaxial test where you add both Whiting and Silica. I've attached a test I did where I increased Silica going left to right, and increased Whiting going top to bottom.

I'm not claiming you'll get a stable glaze this way, since I think Matt recommends some boron for cone 6 glazes. But I also think the tests he did on stability didn't involve iron, so I'd be reluctant to  extrapolate from them. I should point out that I haven't taken his course, so I could be completely wrong about this.

Pieter, This is a most interesting way of setting up test tiles for a line blend. When you fire, do you stand it up on end or lay it flat? If flat how do you tell how how runny the glaze is? I like it!

[curt]

5 hours ago, GreyBird said:

Curt, I am looking for this thread and not finding it. Can you give more info. or post a link here?

Muchas Gracias!

Hi Mary I just searched "currie tile" using the search function in the upper right hand corner of this page and it came up right away, about the 5th entry down.  Maybe your search function isn't working?  Anyway, here it is pasted below.  Get a cup of tea before you dive in.... 

Your clay is a natural candidate for this technique.  If you get interested, as you will see there are many people on this forum who can lend a hand. 

 

 

[curt]

3 hours ago, GreyBird said:

Pieter, This is a most interesting way of setting up test tiles for a line blend. When you fire, do you stand it up on end or lay it flat? If flat how do you tell how how runny the glaze is? I like it!

LOL Mary, not sure exactly what Pieter is showing us on this tile but I am pretty sure it is a currie tile (or at least half of one)!  Each cell has a slightly different chemistry than its neighbors.   One can of course use a currie-format tile like this to do a standard line blend or biaxial blend, but this is somewhat different to the (pretty specific) technique Ian Currie developed, as outlined in his books. 

The standard currie technique uses a 35 cell (5 x 7) tile to explore systematic variations in clay, silica and fluxes.  Since all standard currie tiles are constructed in the same way, once you understand the system, you can look at anyone else's 35 glazes on a currie tile and quickly understand what all 35 cells are telling you.  And Currie has some clever tricks for easily turning 4 mixed glazes into 35 using volumetric blending, so the process is not as time consuming as you think.

When you look at the thread I pasted just above you will see many of these! 

[curt]

7 hours ago, GreyBird said:

So now that I have sufficiently played around on my own, I decided to revisit the insight software and low and behold... I can now glean some info. from it. For instance, if I am reading it right, it says my Si/Al ratio is 5/1 which is good. It also says that my R2O:RO is 0.3:0.7 That's not what I got but that's right on target. I'm sure there are you tube tutorials on the software.. I'll look for them. Maybe the software made and adjustment to correct the ratio? Or is my Hudson Valley Clay perfect to use as a semi Matt glaze, as is?  My UMF Numbers were all slightly different. For instance I had 57.72 Si and insight changed it to 59.08% in the Auto Unity Formula Analysis.

I can't wait, I'll fire up a tile tonight!!!

Mary, one of the things you need to know as you go down this road is the Loss on Ignition (LOI) for your Hudson clay.  Do you know this number?  LOI is how effectively how much of your clay goes up the chimney as organic burnout and volatile gases when you fire a dry sample to (usually) 1000 degrees Celsius.  It is calculated as a weight % by a before and after weighing.  Normally it would be reported on your original lab analysis but I did not see it there, and I have not seen it mentioned anywhere in this thread.  If you don't see it you may call back the lab and ask them, because it is clear they ignited your sample, but unclear if they tracked this number.  If not, you can carry out the test yourself in you own kiln, but it is better to get the lab's official number if they have it, because they do it more precisely.

The absence of the LOI (which is a part of the chemistry of the clay) may explains why the precentages Insight shows are slightly different from what your lab analysis showed.  Did you enter any number in the LOI box when inputting your chemistry into Insight?  If so it should be reported on the picture above just under Expansion. 

[GreyBird]

2 hours ago, curt said:

Hi Mary I just searched "currie tile" using the search function in the upper right hand corner of this page and it came up right away, about the 5th entry down.  Maybe your search function isn't working?  Anyway, here it is pasted below.  Get a cup of tea before you dive in.... 

Your clay is a natural candidate for this technique.  If you get interested, as you will see there are many people on this forum who can lend a hand. 

 

 

I see, yes, thank you. My search tool is working as I did find his page and read through it but ut seamed to be a Buch of people searching for the page... I had missed the link to the actual information embedded within the thread.

[GreyBird]

2 hours ago, curt said:

Mary, one of the things you need to know as you go down this road is the Loss on Ignition (LOI) for your Hudson clay.  Do you know this number?  LOI is how effectively how much of your clay goes up the chimney as organic burnout and volatile gases when you fire a dry sample to (usually) 1000 degrees Celsius.  It is calculated as a weight % by a before and after weighing.  Normally it would be reported on your original lab analysis but I did not see it there, and I have not seen it mentioned anywhere in this thread.  If you don't see it you may call back the lab and ask them, because it is clear they ignited your sample, but unclear if they tracked this number.  If not, you can carry out the test yourself in you own kiln, but it is better to get the lab's official number if they have it, because they do it more precisely.

The absence of the LOI (which is a part of the chemistry of the clay) may explains why the precentages Insight shows are slightly different from what your lab analysis showed.  Did you enter any number in the LOI box when inputting your chemistry into Insight?  If so it should be reported on the picture above just under Expansion. 

Thanks, No. The lab did not give any LOI number.

[Pieter Mostert]

Curt, I gave a description of the tile in my last post: Silica increases from left to right, and Whiting increases from top to bottom. So it isn't a Currie grid, but the bottom left corner still has the most flux. This is a useful test when your starting glaze doesn't have much clay, but has relatively high alumina.

Mary, I fired the tile flat. This is not an example that shows increased fluidity, but I can dig up some if you're interested. I should add that the results of firing flat vs vertically can be fairly different. There's some discussion in the Currie thread about how to get the most info from flat tiles, including some indication of fluidity.

By the way, the reason Insight gives different UMF numbers than what you calculated is that it doesn't include iron as a flux.

Glazenerd, I haven't heard of iron being involved in shivering. I thought lithium was the main suspect.

[glazenerd]

Just now, Pieter Mostert said:

 

Glazenerd, I haven't heard of iron being involved in shivering. I thought lithium was the main suspect.

Pieter:

The Hudson slip is the glaze. In Mary's early tests, 78% of the recipe was Hudson: to which 8.4% was iron, more specifically magnetite. So effectively, the brittleness/stress normally associated in a clay body from that % of iron,  is being transferred to a thin coat. One of the gaping holes in clay chemistry is the effects of reduced iron on COE. While a calculator may transfer the iron molarity into the total flux column, it does not accurately project changes in COE. 

While the carbon content is fairly low in this clay as indicated by the 2.35% LOI,  the effects on magnetite specifically is unknown. In addition, the nearly 25% natural flux content results in a COE significantly higher than normally found in a formulated recipe. The COE is in the same range as Frost porcelain: approaching 7%. So that compounds the effects of high iron content. I ran her recipe at 60% Hudson addition, while maintaining the 10% lithium addition: which produced no shivering. One of those rarities that does not fit traditional chemistry.

Tom