The Stranger

I've moved my glazing operations outside for the season. A little late this year; we've had a cold, rainy spring. It's nice to be outside whenever possible, and glazing is so messy that indoor clean-up can take a bunch of time I'd rather spend doing something else.

I've had company this week while I glaze for the 6/19 firing. This little cat took up residence on our deck on Monday, and has shown no inclinations to leave since then. He was skinny but shiny and apparently healthy. (He's not so skinny now, since we've been feeding him for almost a week.) He's a little luv, a lap cat - it seems like he must have been somebody's pet.

Actually, I've caught glimpses of him around the neighborhood before, just passing through the yard, for a couple of months; which raises the question: if he has a home to go to, why doesn't he go home? My fear is that somebody just moved away and didn't take him with them. Though he has hardly left our deck, I thought I should give him a chance to go home, if indeed he has a home. So I put a collar on him, thinking that if he goes home and his people see the collar, they'll either keep him in for a while - and I won't see him - or he'll come back without the collar. That was Wednesday. He's still wearing the collar.

I've called the police and humane society, but no one has reported a missing black cat in the area. He's intact, so just feeding him and letting him roam free is not an option; we can't have him making kittens that will themselves become starving strays. Adopting him ourselves is out, also, as we already have five cats, one of whom is very old and deserves some peace. So, on Monday he'll have to go to the shelter. It's the best thing for him; they will neuter him and bring him up-to-date on shots, and test him for catly disease like feline leukemia. They will also keep him for a while in case somebody out there is missing their furbaby!

Thursday Inspiration: Aaron Sober

You can see Aaron's newest work here.

Wait, Earthenware?

Well, yes. Kind of.

Just what I needed, another claybody to keep track of. I made myself a special stamp for the ^6 test pieces, because BMix 5 looks alot like Bmix 10 - unless you fire it to ^10, and then they look substantially different! But that's another post. This post is about these earthenware jars.

Remember I said I was going to have to say goodbye to some of my accounts? I thought one of those would be an account I've had for years with a veterinarian making urns for the ashes of cats. I was sad to do it - it seemed right to me that the urns should be made by a committed cat lover like me - but as I discovered at the end of last year, my old pricing was actually costing me money; and I didn't think they would be able to support the new price points.

Time for some creative thinking. But first, a story:

A couple of years ago, my husband and I lost a pet turtle to pneumonia, but ultimately to old age. His name was Big, to differentiate him from his smaller co-turtle, Red, who has a red stripe on his face. (They don't come when you call, anyway, so the names might as well be practical!) Big was an aquatic turtle, and I couldn't bear to put him in the ground, although I know his spirit had already moved on. What I had was just a shell, so to speak. But still.  So I made a container for his remains out of clay, surrounded him with blueberries and raspberries - his favorite foods, and Doug and I brought the unfired "casket" to the river. We placed it on a passing ice floe. The current carried it away. When the warming day melted the ice, Big's remains were consigned to the river. The greenware casket would of course just dissolve.

It occurred to me that folks who have lost cats might want to do something similar. A container which would hold the cremains until the owner was ready to let go, and then just dissolve in the ground once buried, might be something people would want. It would work for me with only a tiny price increase, because I wouldn't incur firing expenses. I made this suggestion to my contact at the cat doc, who agreed.

These will be stamped and adorned with slipwork; some will be burnished with terra sigilata.

By the way, I was wrong (imagine that!) about one thing: in addition to carrying the unfired urns, they also agreed to also continue to carry the fired urns, at the steep hike I found necessary. Important learning moment: so far no one has said no to the higher prices.

Thursday Inspiration: James Diem

See lots more of James beautiful work here.

What's that Smell?

It smells like...I think it's...propane!

I just shut down my bisque firing, because I can smell propane around the kiln. At first I thought...or told myself I thought...that it was just a leftover puff of gas from when I lit the burner, but three hours later, I still smell propane.

The burner guys can't come to check it out until Friday. It's not a danger; the smell only occurs when the main valve is open, but it is massively inconvenient, as due to classes and family obligations, it will put off the bisque until Thursday the 13th. Arrgh, people are waiting for these pots!! But it can't be helped. I don't want to be the idiot sputtering, "I thought it would be okay!" when my neighborhood blows up.

The glaze firing was going to happen on the 14th - already later than I had hoped. Now I guess it will be the 21st. If you are one of the folks waiting for ware, I'm sorry! I will get it to you as soon as I can.

Flashing Slip to Try

Found this while noodling around in a Pottery Basics Yahoo group.

#1997 Fake Avery Flashing slip opaque white to orange Cone 6 10

15 Newman red or Red Horse clay
84 EPK
1 Soda Ash

Wait, but...Newman Red is a fireclay. Red Horse is an earthenware. How are these interchangeable in this recipe?

Guess I'll have to mix them up and find out.

Progress Report

I've been working on getting out Rewards to my Kickstarter backers this week - cards, pendants, and teabowls all took wing. More of them will go out on Monday, and still more after the next test firing.

Speaking of which! The first batch of glaze conversions - five ^6 versions of Old Yellow, my favorite out of the Watershed Glaze book. The ^10 original looks like this:

Neph Sy     7155
Dolomite    2363
OM-4           482

Add:
Zircopax     1792
RIO             240

That's kind of a weird recipe, right? With like 18% opacifier added after the total. This sounds like a job for Glazemaster!  The first thing I had to do was rebalance the recipe so the only ingredient below the total line was red iron oxide. After I do that, the recipe looks like this:

Old Yellow
Cone:  10    
Amount     Ingredient
60.7          Nepheline Syenite
20             Dolomite
4.1            OM #4
15.2          Zircopax

100         Total
Add:
2         Red Iron Oxide

Next I look at the proportions of alumina and silica by the Unity ratios, which the software kindly tells me, otherwise I'd be up all night counting atoms. Alumina is at 0.429; silica is at 2.106. Remember these are relative to the proportion of flux, which is always set to 1.Then I'm gonna compare those numbers to the ranges I found in Cushing's handbook. (There's a way to compare to limit formulas within the software also, but I've got the Cushing numbers right here in front of me.)

According to the good professor, in a satin matte cone 10 glaze, alumina should fall wiht in the range of 0.25-0.6. So we're good there. Silica should be within the range of  2.0-5.0. Also good.

To change this to a ^6 glaze I have to add a a flux.( I can't just increase the flux - dolomite - that is already present, because it's not a strong enough flux at ^6 to persuade the silica to melt.) But adding flux is going to mess up those ratios that I've been talking about, so depending on what I add - a commercial frit, or a material like gerstley borate or lithium - I may have to add more silica or clay (the usual source of alumina in a glaze.) Here are the test recipes I came up with:

Old Yellow ^6 Test 1

Cone: 6 Color: Cream/yellow

Firing: Salt/Soda Surface: Semiglossy

Amount       Ingredient

50.5             Nepheline Syenite

16.7             Dolomite

3.4               OM 4

12.7             Zircopax

12.5             Gerstley Borate--1999

4.2               Silica

100 Total

Add

2 % Red Iron Oxide

Old Yellow ^6 Test 2

Cone: 6 Color: Cream/yellow

Firing: Salt/Soda Surface: Semiglossy

Amount         Ingredient

55.2              Nepheline Syenite

18.2              Dolomite

3.7                OM 4

13.8              Zircopax

9.1                Frit--Ferro 3134

100 Total

Add

2% Red Iron Oxide

Old Yellow ^6 Test 4

Cone: 6 Color: Cream/yellow

Firing: Salt/Soda Surface: Semiglossy

Amount        Ingredient

52.8              Nepheline Syenite

17.4              Dolomite

3.6                OM 4

13.2              Zircopax

13                 Frit--Ferro 3185

100 Total

Add

2% Red Iron Oxide

Old Yellow ^6 Test 3

Cone: 6 Color: Cream/yellow

Firing: Salt/Soda Surface: Semiglossy

Amount            Ingredient

48.1                 Nepheline Syenite

15.9                 Dolomite

3.2                    Ball Clay--Old Mine #4

12.1                 Zircopax

15.9                 Frit--Ferro 3134

4.8                   Silica

100 Total

Add

2% Red Iron Oxide

 Old Yellow ^6 Test 5

Cone: 6 Color: Cream/yellow

Firing: Salt/Soda Surface: Semiglossy

Amount        Ingredient

50.6             Nepheline Syenite

16.7             Dolomite

3.4               Ball Clay--Old Mine #4

12.7             Zircopax

16.6            Frit--Ferro 3110

100 Total

Add

2% Red Iron Oxide

 I mixed all of these up in the glaze kitchen, storing them in those little plastic tubs you buy at the supermarket to keep leftovers in. (Plan A - to eat enough Talenti Gelato to use those containers - was a non-starter, even in hot weather like we've been having.)

I have a ^10 firing coming up, as I am trying to keep up with all my outlets at the same time I execute this project. (That wasn't the original plan, but baby, things change. Moron that later.) That should happen next week, with the next ^6 test hard on its heels.

Remember the 80s?

Not the decade...I'm talking the 80s Fahrenheit. Here in Maine we went straight from 60º to 90º+, and let me tell you, I deserve some kind of medal for working right through it. Or maybe a tiara, because I am sweating like a princess, here.

This morning, before it was too beastly, I brought all my greenware down into the kilnshed, from where I will load the kiln later tonight. I've also been making teapots and lidded jars, and slip trailing everything in sight.

My studio is in a former attic space, which some prior owner raised the roof on. It has only one north-facing window, and for once this is a plus! The studio stayed tolerable for most of the afternoon. But now it's 4 pm, the hottest part of the day, and I am taking a break until evening, when I will load the kiln.

For now, enjoy a little song that seems from our missing 80s:

One More Tidbit

Another helpful rule of thumb from Cushing's Handbook:

Very broadly: If the proportions (by molecular weight) of silica to alumina in a glaze in the range of 8-10, the glaze will probably be glossy and transparent.  This (and the next bits) does not account for which flux is used; a high proportion of magnesium (for example) used as a flux will cause the glaze to be matte regardless. The proportions of silica to alumina can go as high as 18 to 1.

If the proportions are in the neighborhood of 5-8 to 1, this will probably be a satin or waxy glaze. Depending on the flux.

If the proportions of silica to alumina are 1-5 to 1, this will likely be a stony matte glaze.

Charlotte Smith

We have yet another chance today to learn to dance in the rain, here in Maine. (A friend observed that we must be slow learners!) The pots that I left unwrapped all day yesterday and then overnight, are still too wet to trim. My plan is to throw some ^6 test pieces, now that I have a boatload of recipes to test, and to generate a boatload more recipes with my new toy.

My New Toy

Your authoress is one happy Potterchik today! I've been taking Glazemaster for a whirl, and boy, if any of these test glazes works out, I can't give them my $40 fast enough. It does exactly what I want glaze calculation software to do: allow me to enter the recipe in percentage by weight - the way most potters use recipes - and then it tells me what the molar percentages are, and the Unity formulas. THANK YOU!! It also re-calculates the percentages when you add new ingredients to bring the total back to 100; that's probably obvious, but just think, I'll never screw that up by hand again!

So, I can type in a ^10 recipe, move it to the right side of the page so it is available for comparison; then copy it to the left and start typing in changes intended to lower the maturation temperature. The software tells me as ai go along what the Unity proportions are, so I can make additional changes if the proportions of silica and alumina get out of whack. It also tells me its thermal expansion value - which I'm finding tends to go up when I add frits - so I can keep that within an acceptable level. This should create a finished glaze which has properties similar to that of the original.

I can also compare both the original ^10 glaze and its new ^6 little sister to the limit formulas I got from Cushing's Handbook, and determine if they fall within the acceptable range. I'll write another post with the original glazes and their ^6 derivants when I have some results to show you.

I will say, though, despite my frustration with the first software I tried - Insight - that their reference library and help resources are far superior to Glazemaster. I feel sort of guilty that whenever I run into a question that's not covered in Cushing, I go to the Digitalfire Reference Database.

**hey, just in case you were wondering...okay, you probably weren't wondering...LOI, used in glaze chemistry, stands for Loss on Ignition, which refers to the weight a material loses upon firing.

PS. - Insight apparently does this - the material-by-weight thing - as well; I've just had an email from its technical staff. I couldn't figure it out even with the intro video, but maybe you can. Lots of people do swear by the program. 

Okay, I Know What I Said But...

...this is really really helpful, and sometimes I absorb and remember things better when I type them up myself. So! I really am studying.

I created this table to help me remember the limit formulas - the range of ratios of flux, alumina and silica - for glossy, satin, or stony surfaces at ^6 and ^10. Remember these are ratios of molecule counts - we still haven't gotten to how they translate into percentages by weight, yet:

This is a simpler version of the table that Professor Cushing presents, which includes proportion ranges of specific fluxes, and of boron, an alternative low-temperature glassformer (if I am understanding that correctly.) Just this alone is (well, will be) tremendously helpful.
Once I get the translation part down, I'll only have to compare a glaze to this table to know if it has the appropriate proportions of silica and alumina to flux to work at my given cone level, and not be too soft or too viscous. There is great overlap in the percentages, because much depends on which specific fluxes are used, and because the categories are pretty broad: "Satin," for example, could describe a waxy shine or an eggshell matte.

Anyway, back to the book. Still a lot to learn! Hope this is helpful for someone out there in TV land. 

No Shortcuts

Thank heaven for Professor Cushing! It appears that despite my efforts to find ways around it - winging it, using software - I am going to have to learn to understand Unity Molecular Formulas. Very basically, I know what Unity Molecular Formulas are; they express the glaze formula as a count of molecules of glassformer, stabilizer (alumina), and flux, with the amount of flux weighted to one (that's why it's called Unity, get it?) and the silica and alumina amounts expressed relative to the flux. I just don't understand how to translate them to batch recipes that I can use. That's where the good professor comes in.

I few months ago, I bought a copy of his handbook. the link above goes to Amazon, the second to an address from which you can purchase from Cushing himself. It's probably worth getting an envelop & stamp, as I see the notebook is selling on Amazon for $190; whereas the professor offers it for $28. It's a great book utterly packed with knowledge and ideas; this particular chapter, though invaluable to me, happens to be on the boring side. I feel like an undergrad at Iowa State again: those soft chairs at the Parks Library were just way too comfortable. If I were sitting there now I'd fall asleep for sure.

And, clearly, I am utilizing another of my undergrad work-avoidance techniques: simple procrastination. Writing a blog post about RO Unity is miles better than reading about it!

Stop that, Lori. Stop it right now. If I post again before noon, EST, somebody remind me that I am supposed to be reading.