Raw Materials

[Marko]

Does the mix of elements in a bag of raw material change from time to time? And is it important to know these things when 'm mixing glazes. I'm starting my (oh what am I getting myself into, now) glaze chemistry journey. I'll learn it, or you can find me at Bellevue sanatorium. I want to know cause, looking at Digitalfire and trying to understand it seems complicated. Like what's a Unity Formula? I was watching a John Britt YouTube video; 

A Super Simple Analogy to Help You Understand Glaze Structure, and he mentions that RM can have a combination of different elements.  Okay, maybe I should just stay with, Tried and True, but I'm curious.     

[MatthewV]

Industrial uses which buy train car loads of materials dictate the standards of acceptable variations. Potters buying 50# bags don't really matter to the suppliers. Yes, most naturally mined materials have a level of variation. Feldspar is a rather broad term chemically speaking.

 

It is as complicated as you wish to make it.

[neilestrick]

The unity formula is the molecular ratio of the elements in a particular glaze. Those elements are supplied by the raw materials in the glaze recipe. The unity formula allows us to compare glazes more accurately than looking at a recipe, since a glaze with 15% calcium carbonate by weight in the recipe isn't necessarily 15% calcium in it's final fired state. Also, many materials supply more than one element, so the unity formula shows that. The unity formula also allows us to substitute materials, since there are numerous materials that can supply each element. It also allows us to make specific changes to the glaze that can't easily be made by changing the raw materials in the recipe.

 

Example: I have this glaze that I love, and I use it all the time. The recipe contains materials that are all mined here in the USA. If I move to Australia, I won't have access to those specific raw materials any more, but I will have access to other materials that can supply the necessary elements to make that glaze. So I can take my recipe and convert it to the unity formula, then convert it to a new recipe using the materials I have available. The recipe is different, but the molecular makeup of the glaze is the same.

 

Another example: I need to increase the alumina content in a glaze. There's no alumina in the recipe- it's being supplied by the feldspar and the kaolin. If I increase the feldspar, it will also increase the potassium and sodium and silica. If I increase the kaolin, it will also increase the silica. So I have to go into the unity formula, increase the alumina in the formula, then convert it back to a recipe.

[Mark C.]

One last thought is over time as materials are mined from the earth they do change as the ore is never exactly the same everywhere . I have seen this over time especially with feldspars.

The ones I used in the 70's are not even offered to you anymore and when they got near the end the analysis changed.

Heck Custar feldspar changed a few years ago

Sometimes great things are not ever again available like Kingman feldspar (man am I glad I bought 3000#s in 1982)

or albany slip ( still glad I have 150#s)

so to strictly answer your question yes they can but on a day to day glaze mixing you do not need to sweat it.

[glazenerd]

Mark: You mean the old stuff like this -

 

Nerd

[Mark C.]

Nerd I have a full bag of that still unopened as thats not really older stuff just harder to come by now-I meant older stuff like kingman feldspar or Albany slip which is long gone

My materials storage area was recently redone these shelves are two bags deep each with the bottom 3 bags deep

 

 

 

[Dick White]

Marko, in one of my other lives (sometimes I wish I were a cat and had only 9 lives to keep organized...) I teach the glaze chem class at one of our local studios. You mentioned the unity molecular formula. Yes, trying to understand the UMF will make your head explode. However, there is no higher math involved, i.e., no abstract numbers or theoretical constructs as in algebra or calculus; there is only basic arithmetic - but so much arithmetic running in so many directions that it is hard to keep it all straight enough to wrap your head around, hence the inevitable explosions. Once all the arithmetic is done, the answer is quite simple and elegant (a word used by mathematicians to describe chaos after it has been tamed) to use. In essence, after lining up all the oxides of a glaze in orderly queues and counting the number of molecules of each type of oxide, you will find that for every 100 molecules of flux oxides, there typically will be between 25 and 50 molecules of alumina and 300-500 molecules of silica, and various numbers of a few other oxide molecules. Within the fluxes, the proportions of the different flux oxides will help you understand some of the characteristics of the resultant glaze, e.g., some flux types cause a glaze to be glossy and other types cause it to be matte.

 

WTF, how did he get there, head explodes again. So I developed a spreadsheet that lays bare all the arithmetic, step by step, line by line, for a sample glaze, so you can see exactly how the UMF is calculated. Within the spreadsheet, you won't have to do any arithmetic in your head or with your handy pocket calculator, the arithmetic is all done for you, but exposed so all you have to do is run your finger up and down the columns to see where this is multiplied by that, and then we use that number to multiply by the next one, and finally at the bottom, bingo, there is the UMF for that glaze recipe. This spreadsheet is not a working tool, only a teaching tool to help you fully understand where the UMF numbers come from. When you are working a glaze UMF, you should use glaze calculation software on your computer to keep the database of raw materials analyses and do all the head-exploding arithmetic for you. So here is my offer - I don't think there is a repository here on the forum for sharing files except pictures (somebody correct me if I'm wrong), so PM me and I'll email it to you.

[High Bridge Pottery]

I like to think of it all as building blocks. If you look at the periodic table everything has been blocked out for you with their atomic mass or mass in relation to each other as I like to think.
 

The atomic mass (ma) is the mass of an atomic particle, sub-atomic particle, or molecule. It is commonly expressed in unified atomic mass units (u) where by international agreement, 1 unified atomic mass unit is defined as 1/12 of the mass of a single carbon-12 atom (at rest).

 

 
So we start with the atoms in the table and build a nice molecule of Silica and one of Zinc oxide. A block (atom) of Si is 28.1, Zn is 65.4 and Oxygen 16.0.
 
SiO2 = 28.1 + 16.0+16.0 = 60.1 mass (this can be anything, right now it is just a ratio to 12ths mass of a carbon atom)
ZnO = 65.4 + 16 = 81.4 mass
 
So if I took my singular molecules and could weigh them I would have 60.1 + 81.4 = 141.5 atomic mass and 1 molecule of each. If I go to put this into digital fire it comes back with a unity formula 1 to 1. All looking good. My two molecule glaze is coming along nicely.
 

 
Now I would like to try a new mix of molecules but I only have one of each. So I take out my atom cutter and slice off bits of each till I can get 50 atomic mass of silica and 50 atomic mass of zinc oxide. This is 83% of my molecule of silica and 61% of my molecule of zinc oxide.
 
 
 
Now again we go across to digital fire with these atomic mass or ratio mass as I like to think. You can see it gives me the unity formula 1.35 to 1. So I have taken 50 atomic mass (83%) of my silica molecule and 50 atomic mass  (61%) of my zinc oxide molecule and that gives me a ratio of 1.35 silica atoms for every 1 zinc oxide atom.
 

 
I hope this explains a little better that unity formulas are just ratios of oxides to each other. You can imagine them just like singular blocks even though we are messing about with billions of atoms. The ratios stay the same. The only difference between unity and any other way you can write a ratio is unity totals flux to one for ease of comparison to other glazes.

 

The thing that makes calculating unity hard is because you have a material that has certain percentages of atoms. You then have a percentage of this material in the total recipe so working it out requires two layers of calculations. First what the atoms weigh in your materials, then how many of those atoms in relation to every other atom you are adding from other materials. Software is there to do that for you and spit out an atom ratio you can use for comparison.

[glazenerd]

Mark:

 

 You need to open a supply store- you get ten extra points for organization. I watch our local auction houses websites and come across items from time to time. Two weeks ago went to an estate sale that had "pottery tools and supplies." Most all of it was from the 80's, but got excited when I eyeballed 3 bags of the old Pemco 283 frit. One had frit that was half full and rock hard, the other two the lady had dumped something into- going to guess some kind of feldspar. The G-200 shown above I paid $10 for 130 lbs at an auction.

 

Joel: good lesson..

 

Nerd

[Mark C.]

Nerd if you come across any talc from the 70-80s or early 90's I'll take it.

Desert talc or C-30 talc.

[Guest JBaymore]

It is as complicated as you wish to make it.

 

 

It can get MORE complicated than you wish to make it! 

 

But it is also way too easy to OVER complicate it.

 

There are two general ways to look at glazes... "materials based" and "oxide based".  A lot of studio potters tend to focus almost solely on "materials based" approaches.  The "chasing glaze recipes" addiction is a part of this thinking.  This leaves them missing about half the available resources to understand what is going on.  That being said, a slavish total "oxide based" approach overlooks that the stuff we typically use is coming from impure, variable raw materials, and those raw materials have properties that impact HOW they enter into the melt and also how they behave in application. 

 

So you need both halves of the picture to really master things.

 

For the studio artist, you only need to understand the things that are in the pervue of the work you are trying to do.  The field of ceramic chemistry is enormous... and no one 'knows it all'.  If you weant to be a ceramic engineer... then you need to know a lot more of that breadth.  But if you just want to produce good studio work...... you need to know what you need to know.  No more....no less.

 

A glaze RECIPE is like the instructions for blending raw materials for making a cake.  A glaze FORMULA is the technical analysis of the cake AFTER it is baked.  A UNITY formula is set up in a way that lets people compare apples to apples and oranges to oranges.

 

best,

 

.......................john

[glazenerd]

Mark:

 

So noted!!

 

Nerd

[Marko]

Industrial uses which buy train car loads of materials dictate the standards of acceptable variations. Potters buying 50# bags don't really matter to the suppliers. Yes, most naturally mined materials have a level of variation. Feldspar is a rather broad term chemically speaking.

 

It is as complicated as you wish to make it.

 

Industrial uses which buy train car loads of materials dictate the standards of acceptable variations. Potters buying 50# bags don't really matter to the suppliers. Yes, most naturally mined materials have a level of variation. Feldspar is a rather broad term chemically speaking.

 

It is as complicated as you wish to make it.

So does that mean every time I buy a 50# bag, I will have to get a analysis of it's content, so I can make any adjustments to a glaze I make, in order to have consistent results? Thanks

[Marko]

I like to think of it all as building blocks. If you look at the periodic table everything has been blocked out for you with their atomic mass or mass in relation to each other as I like to think.

 

The atomic mass (ma) is the mass of an atomic particle, sub-atomic particle, or molecule. It is commonly expressed in unified atomic mass units (u) where by international agreement, 1 unified atomic mass unit is defined as 1/12 of the mass of a single carbon-12 atom (at rest).

 

 

So we start with the atoms in the table and build a nice molecule of Silica and one of Zinc oxide. A block (atom) of Si is 28.1, Zn is 65.4 and Oxygen 16.0.

 

SiO2 = 28.1 + 16.0+16.0 = 60.1 mass (this can be anything, right now it is just a ratio to 12ths mass of a carbon atom)

ZnO = 65.4 + 16 = 81.4 mass

 

So if I took my singular molecules and could weigh them I would have 60.1 + 81.4 = 141.5 atomic mass and 1 molecule of each. If I go to put this into digital fire it comes back with a unity formula 1 to 1. All looking good. My two molecule glaze is coming along nicely.

 

 

Now I would like to try a new mix of molecules but I only have one of each. So I take out my atom cutter and slice off bits of each till I can get 50 atomic mass of silica and 50 atomic mass of zinc oxide. This is 83% of my molecule of silica and 61% of my molecule of zinc oxide.

 

 

 

Now again we go across to digital fire with these atomic mass or ratio mass as I like to think. You can see it gives me the unity formula 1.35 to 1. So I have taken 50 atomic mass (83%) of my silica molecule and 50 atomic mass  (61%) of my zinc oxide molecule and that gives me a ratio of 1.35 silica atoms for every 1 zinc oxide atom.

 

 

I hope this explains a little better that unity formulas are just ratios of oxides to each other. You can imagine them just like singular blocks even though we are messing about with billions of atoms. The ratios stay the same. The only difference between unity and any other way you can write a ratio is unity totals flux to one for ease of comparison to other glazes.

 

The thing that makes calculating unity hard is because you have a material that has certain percentages of atoms. You then have a percentage of this material in the total recipe so working it out requires two layers of calculations. First what the atoms weigh in your materials, then how many of those atoms in relation to every other atom you are adding from other materials. Software is there to do that for you and spit out an atom ratio you can use for comparison.

Wow, this is me, at first,  , then  , then  and finally  .  This is quite helpful. I will have to print it out if I can. I like your examples. Did you right the book?   Thanks

[Guest JBaymore]

Mark,

 

The answer to that question is the standard, "It depends".

 

To start with... how critical is the formulation of a particular recipe to slight variations in composition?  A "good" recipe / formula should have some "tolerance".  If there is little tolerance..... then you need to have tighter controls.

 

Second....... how devastating would the loss of work be?  One piece that took a total of an hour to produce...... well... maybe that itself is the "test work" for the new material batch.  But $100,000 worth of production?????  Well... that would be kinda' dumb to do.

 

In industry, they test new materials batches before putting them into production.  In fact in Japan... many studio type artists do this too. 

 

SO let's say you have "Glaze Batch A" that is a staple in your studio.  You mix it up in 40 gallon batches.  So you have a batch of glaze that lasts a certain amount of time in production work.  As that glaze batch starts getting low, you know you need to make more soon.  So you look at your raw materials inventory, and discover that Feldspar Z that makes up 20% of that glaze is just about out.  So you order more.  This is now a new bag from the supplier. 

 

Now you need to mix up more of "Glaze Batch A".  What you SHOULD do is mix up a test batch...... say 1000 grams or so.... and glaze some work with that mixture right along with the other production work using the original "Glaze Batch A" bucket.  Fire tham together.  It is a comparison test.  If the new batch looks the same and tests the same (crazing, abrasion, etc.) then you can mix up the replenishment for the big 40 gallon batch.  If it is different... you are now on the path of finding out WHY it is different...and taking action to adjust the recipe appropriately.

 

A long, long time ago... in a galaxy far, far away....... I did not follow this approach with a new shipment of custom clay body... and unloaded an entire noborigama load into my shard pit.  It almost bankrupted me.  And I lost some good accounts because of it.

 

best,

 

.......................john

[Callie Beller Diesel]

 

Industrial uses which buy train car loads of materials dictate the standards of acceptable variations. Potters buying 50# bags don't really matter to the suppliers. Yes, most naturally mined materials have a level of variation. Feldspar is a rather broad term chemically speaking.

 

It is as complicated as you wish to make it.

 

 

Industrial uses which buy train car loads of materials dictate the standards of acceptable variations. Potters buying 50# bags don't really matter to the suppliers. Yes, most naturally mined materials have a level of variation. Feldspar is a rather broad term chemically speaking.

 

It is as complicated as you wish to make it.

 

So does that mean every time I buy a 50# bag, I will have to get a analysis of it's content, so I can make any adjustments to a glaze I make, in order to have consistent results? Thanks

Short answer, no.

No every time. But if you change bags of certain materials that are known to shift over time, it's a good idea to mix a 100g test batch of a glaze to make sure all is still within acceptable parameters before committing to a 20 kg bucket of anything.

A little of it will depend on the glaze recipe as well. To continue the baking analogy used above, some glazes are like baking cookies: there is a certain amount of leeway, and they're forgiving. Some are like soufflés: make one wrong move and it fails.

[jrgpots]

I was just gifted 100 lbs of core samples from a mine in AZ. The sample were from the 2,500 ft depth in the mine. They are red, tan, and blue rods. Each sample is 1.5" diameter and 12-14" long.

 

So what do you do with something like that?

 

Jed

[Callie Beller Diesel]

Find out what kind of rock they were drilled from. Whoever got you the core sample could probably ask one of the geologists that examined the core for specifics. You might also want to inquire about th slurry used as lubricant for the drill. Some of it is toxic. (In my neck of the woods slurry is often contaminated with raw petroleum of some kind.)

[Babs]

ANd in pursuit of the same and the repeatable, are some babies being thrown out with the bathwater??

(Ignoring JB's nightmare here....)

[Marko]

Mark,

 

The answer to that question is the standard, "It depends".

 

To start with... how critical is the formulation of a particular recipe to slight variations in composition?  A "good" recipe / formula should have some "tolerance".  If there is little tolerance..... then you need to have tighter controls.

 

Second....... how devastating would the loss of work be?  One piece that took a total of an hour to produce...... well... maybe that itself is the "test work" for the new material batch.  But $100,000 worth of production?????  Well... that would be kinda' dumb to do.

 

In industry, they test new materials batches before putting them into production.  In fact in Japan... many studio type artists do this too. 

 

SO let's say you have "Glaze Batch A" that is a staple in your studio.  You mix it up in 40 gallon batches.  So you have a batch of glaze that lasts a certain amount of time in production work.  As that glaze batch starts getting low, you know you need to make more soon.  So you look at your raw materials inventory, and discover that Feldspar Z that makes up 20% of that glaze is just about out.  So you order more.  This is now a new bag from the supplier. 

 

Now you need to mix up more of "Glaze Batch A".  What you SHOULD do is mix up a test batch...... say 1000 grams or so.... and glaze some work with that mixture right along with the other production work using the original "Glaze Batch A" bucket.  Fire tham together.  It is a comparison test.  If the new batch looks the same and tests the same (crazing, abrasion, etc.) then you can mix up the replenishment for the big 40 gallon batch.  If it is different... you are now on the path of finding out WHY it is different...and taking action to adjust the recipe appropriately.

 

A long, long time ago... in a galaxy far, far away....... I did not follow this approach with a new shipment of custom clay body... and unloaded an entire noborigama load into my shard pit.  It almost bankrupted me.  And I lost some good accounts because of it.

 

best,

 

.......................john

Thanks John, This does help. I appreciate you taking the time to help me unravel the great mystery. Thank you.

[Marko]

 

 

Industrial uses which buy train car loads of materials dictate the standards of acceptable variations. Potters buying 50# bags don't really matter to the suppliers. Yes, most naturally mined materials have a level of variation. Feldspar is a rather broad term chemically speaking.

 

It is as complicated as you wish to make it.

 

Industrial uses which buy train car loads of materials dictate the standards of acceptable variations. Potters buying 50# bags don't really matter to the suppliers. Yes, most naturally mined materials have a level of variation. Feldspar is a rather broad term chemically speaking.

 

It is as complicated as you wish to make it.

So does that mean every time I buy a 50# bag, I will have to get a analysis of it's content, so I can make any adjustments to a glaze I make, in order to have consistent results? Thanks

Short answer, no.

No every time. But if you change bags of certain materials that are known to shift over time, it's a good idea to mix a 100g test batch of a glaze to make sure all is still within acceptable parameters before committing to a 20 kg bucket of anything.

A little of it will depend on the glaze recipe as well. To continue the baking analogy used above, some glazes are like baking cookies: there is a certain amount of leeway, and they're forgiving. Some are like soufflés: make one wrong move and it fails.

 

Thank you Callie. I'll definitely test before making a commitment to large batches. 

[Marko]

ANd in pursuit of the same and the repeatable, are some babies being thrown out with the bathwater??

(Ignoring JB's nightmare here....)

IDK? But I do need a bath, now that you mention it. hehe 

[Marko]

So bottom line. I learned many good things here. Thanks to all. So, now, I will continue learning on Digital Fire.  I will keep records of the raw materials I use in glaze recipes I want to use. Then do small batch tests, record the results and then make a full batch. Then when making a replenish batch repeat, test and record. Right?

[Babs]

only if you are going to use a new delivery of glaze ingredients. Ones in studio are the ones you've tested, right?

[Guest JBaymore]

If the glaze materials you have on hand are the ones that went INTO the working batches of the glazes you use....... and those glazes are OK... then you do not need to test before EACH new mixing (as long as you are CAREFUL about your mixing procedures).  If the materials you have on-hand when you mixed the last batches are in NEW un-used bags....... check the lot numbers on the bags.  If it is the same lot number you should be OK without testing them.  If there is no lot number.... you should test.

 

To help avoid surprises, mixing procedures should be "standardized, and you should make up a checklist of the ingredients that you check off the same way every time. If you check the item off when you pour it into the glaze bucket.... you should do it at that point ALL the time.   Then when the phone rings .... and you come back... you know if you already added that material to the partially weighed out glaze or not.

 

The smaller the test batch, the more careful you need to be on calibrating the scale, cleaning the tools, and weighing the materials.

 

On a somewhat related topic:

 

One of the "classic" mistakes up professor types see all time is students who suddenly decide on using a new glaze/slip/clay body for a body of work for something like their senior thesis show... and do not do much if any testing work with the new-to-them material.... and put it right into production of the new body of work.  Then when it screws up in the firing, they get all bent out of shape at their "bad luck". 

 

best,

 

..................john