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. 

Thursday Inspiration: Laurie Pollpeter Eskenazi

Laurie's vases were my favorites, but she makes all kinds of awesome stuff. Check it out here.

Hat tip to Joanna Skolfield of Blarney Stone Pottery. 

New Items in the Pottery Shop!

As long as they are this time of year, the days are not nearly long enough. I've been working pretty much steadily since I got up this morning around five, and it's nearly seven now, and I can see there are things on my list that are. not. going to happen. I did manage to finish some butter dishes, take some photos, and get to the gym - which accomplishment was promptly negated when I ate a hefty slice of my prop! Seemed a shame to waste it. :/

I also got my Kickstarter thank-you cards signed and ready to go out, spent a little time navigating around Glazemaster, and listed a few items on my website. Click the captions to see more photos or to purchase.

Set of Four Dessert Bowls, $120

White and Silver Striped Mug, $36

Blue and Russet Cake Stand, $125

I've still got berry bowls to trim, and promises to keep, and miles to go before I sleep.

Time to Prune?

You may remember my way-too-angsty decision back in November to raise my prices for the New Year? This has so far been a fine, fine thing, as I've met no real resistance - I'm still selling everything I can make (current work - I haves tons of old inventory), although I make somewhat less stuff. Though I was never aware of hurrying before, I do take more time with each piece now. The higher price point has sort of given me permission to do so, and it seems like, if someone is paying $95 (or more) for a serving bowl, it ought to be a damn fine serving bowl in every detail.

The change has been hard in one way, though: I am only now, as our season here in Maine gears up, realizing that I will have to say goodbye to some old consignment accounts, due to making fewer pots. These are folks I've done business with for awhile; they are friends, and I feel like a jerk saying, Sorry! Demand exceeds supply! On the other hand, consignment requires a ton of ware to be made and sitting on shelves out in the world, while I wait for checks to come in; and it requires a fair amount of maintenance in the form of record-keeping and the switching out of work. If I'm spread too thin, it makes sense for the outlets returning the smallest or rarest checks to get cut.

I'm already getting practiced at the art of saying no to new consignment outlets which contact me, but Good Business demands that I prune existing accounts, too, if they underperform. In my head I know it's better for the stores as well: surely they'd rather use their limted shelf space for work that would fly off, right?

Maybe I won't do it right away. It's May, in Maine; pulling work now gives them a scant couple f weeks before the tourist season begins in earnest on Memorial Day to replace me. That seems like a shitty thing to do. And who knows? Maybe this will be the year that one or more of them really takes off.

Thursday Inspiration: Patrick Coughlin

See lots more of Patrick's intriguing work here.

Groundhog!

Tim Cichocki, a potter from Norridgwock, Maine, and my dear friend, is firing his groundhog kiln this spring!
This will be a three day firing, loading June 20th and firing through the 23rd. Stoking shifts are required, as is a $200 firing fee. Participants are allowed kiln space equivalent to a 4 x 4 pallet full of work. Wood & wadding provided; you bring the pots.Greenware - bone dry, interjects Captain Obvious! - is fine.

Space is limited! Give Tim a shout a tcwoodfire@gmail.com if you want in on this opportunity.