^5/6 Glazes

[Sheryl Leigh]

I am very new to mixing my own glazes - never had a class on it and am trying out recipes out of books and forums.

 

And am not having much luck at all.  So far, I have one success out of John Britt's book, The Complete Guide to Mid-Range Glazes (Ron's Yellow) and a Floating Blue recipe, but have had poor results from Xavier's Warm Jade Green (got this very thin, pearlescent green,) Copper Turquoise (grainy, runny and hardly turquoise,) Tahitian (feels thick, fires out thin,) Krakowsky (supposed to be black but is chocolate brown) & Assad's opalescent white (crawls like crazy) ( the latter two also out of Britt's book).

 

Is it just me?  My studio partner mixed up a half dozen ^10s with *no* problem.  I know there's a ton of variables and I know I need to rein in and start doing smaller batches, but my frustration is mounting. 

 

I have picked up Mastering Cone 6 Glazes by Hesselberth and Roy but haven't had a chance to get though it yet.  And Val Cushing's handbook is next up after that.

 

Any advice is greatly appreciated, as well as commiseration, lol.

 

[glazenerd]

Hi Sheryl:

 

Lots of talented people floating around on the forum that can help you along. Doing a forum search will also give you plenty of reading material. Cone 6 is more sensitive than cone 10: heat work being the primary reason. It also depends on your firing schedule to bend a cone 6. Many fire to 2190F with extended holds, others fire up to 2230F (me) with a short hold. You need to place some cones around (cone 6), it could be as simple as kiln calibration 9controller), or checking for hot and cold spots.

 

The second is formula limits for cone 6: there is a required minimum for alkali/fluxes to melt at cone 6.

 

You stated one was very thin: which could come from the hot part of your kiln.

you stated one was grainy, a sign of an incomplete melt. ( too cold).

If they both came from one firing; then kiln calibration is high on the probable cause list. Ramp cycles can also play a role in melt.

 

From reading your comments, with the knowledge you are using ( and following) proven recipes: kiln calibration/firing ramp cycles are the likely cause.

 

Visit Ron's website @ http://www.ronroy.net/  Read the section on formula limits (in his book); very important info for mixing glazes.

 

Nerd

[Sheryl Leigh]

Hi Nerd,

 

Great advice, thank you.  I will definitely place some cones in my next glaze firing.  My kiln is a fairly lightly used Skutt 1227 and it didn't occur to me that it would vary like that, duh. 

 

I've been leaning towards the alkalinity of my water as a factor (Phoenix, AZ makes its own Calcium carbonate just from the water sources).  Do you think that could also be a problem, or not so much?

 

Thank you, again.  I already feel a little better!

[MatthewV]

Mmm glaze application is also a big factor in success or failure of a recipe. Some need to be thicker for proper coverage. If you mixed in too much water not enough glaze will lay on the surface. This is the single hardest part to control when mixing your own glazes.

 

Measuring specific gravity for each new batch will help.

 

And hopefully you are sieving (80 mesh) them!

[glazenerd]

 

I've been leaning towards the alkalinity of my water as a factor

Actually, your water is glaze friendly: calcium carbonate (whiting) is used as a glaze flux.

Matthew also makes some excellent points.

 

Nerd

[Pres]

I have also found from working with students, if you don't keep a homemade glaze of the ^6 variety mixed up, things settle out too fast. Often compounds needed for color or glaze finish.

 

 

best,

Pres

[bciskepottery]

Are you using Krakowski's Albany Substitute as a glaze by itself or as a substitute for Albany Slip in another glaze? Her intent was to formulate a substitute for glazes calling for Albany Slip -- which is no longer mined. There are several recipes out there for Albany Substitutes. You can shift the color of Albany Substitute towards black by adding up to 2% cobalt carbonate.

 

Xavier's Warm Jade seems to be sensitive to thickness from the times I've used it.

[Marcia Selsor]

Are these for electric firing?

I have been working with ^6 oxidation and reduction since 1980 when I switched from ^10.

I have several glaze recipes with pictures posted in my gallery. I also contributed to Britt's book and Michael Bailey's book on Oriental Glazes with my being the only ^6 glazes in the book.I like Michael Bailey's ^6 Glaze book. You'll find the Xavier's Warm Jade is not food safe. Be careful with that one.

 

These are Oxidation glazes from my gallery:

 

http://community.ceramicartsdaily.org/gallery/image/682-baileys-red-orange-6-oxidation/

 

http://community.ceramicartsdaily.org/gallery/image/3541-cone-6-faux-celedon/

 

http://community.ceramicartsdaily.org/gallery/image/765-6-red-glaze-with-6006-deep-crimson/

 

http://community.ceramicartsdaily.org/gallery/image/772-yellow-glaze/this one is actually using my base from Reduction but fired in Oxidation for the yellow.

[Denice]

Electric Cone 6 & Other Ways with Clay is a forum you might take a look at.  It has groups that test C6 glazes and share the results on line,  you can lurk for free but if you want to ask questions it will cost $10 to join.    Denice

[Min]

Totally agree that glaze thickness makes a huge difference with how the glaze turns out. It's all about trial and error with glaze testing. Some glazes have a little wiggle room for temperature, others are quite sensitive to being fired too hot or cool. (nudge, nudge, use cone packs)

 

For example, with Xaviers Warm Jade Green, it needs to be thick to get the visual texture. Try mixing it up with 100 base to 70 water. On tall test tiles (with room for the glaze to really run) try a single dip, a double dip and another tile with 3 dips. It will run when thick enough, you just have to fine tune how much you want it to run by glaze thickness. If it’s fired to ^5 - 5 1/2 it is more of a satin matte than a gloss. Refiring this glaze will have the glaze running off the pot and loosing the varigation. (also runs more on porcelain than stoneware) Not sure which version of this glaze you are using but the Ron Roy version does get the nod for being “An extremely stable glaze. It should be excellent for functional or decorative work†

 

 

This little cup is the RR version with less rutile and a little titanium dioxide (lined with faux celadon). Subbing part of the rutile for titanium dioxide makes the greens and blues a little less muddy than the original glaze. You can see at the bottom of the cup where the glaze has less variegation I have applied the glaze thinner so it doesn't run onto the kiln shelf and thicker towards the top. 

[Joseph Fireborn]

Testing glazes is one of the hardest parts of pottery. Hang with it. It takes a lot of practice and patience. What people have said above is a great place to start. I would try to work with easier recipes for starting out then stuff with lots of running and variation. Get some simple glazes first so you can make some pots your not frustrated with and start using them every day. Then slowly add some more complex applications and glaze combinations. I have been doing this 3 years and I still am confused about a many things. 

[Sheryl Leigh]

Thank you all, I am overwhelmed with your response!  It jives with my experience that clay people seem to be so generous with their experience and insight.

 

Quick response:
Matthew - I have started sieving at 80 mesh, the Tahitian and the two that worked were both done that way.  Re: spec grav - does every glaze have it's own specific gravity or do I just have to figure it out as I go?  I will take your advice about application, combined with Min's advice about testing.

 

Glazenerd - good to know re: water.  Goodness knows this stuff should be good for something, lol. Harder than a rock.

 

Pres- Yes sir, I've noticed the settling.  My last instructor said the only way to cope with that was to stir everything with your hands.  I politely declined.

 

bciskepottery - you hit the nail on the head.  I did not understand the Krakowski's use.  But now I have a nice chocolate brown that I can recommend....  I will have to post what my Xavier's warm jade looks like, you won't believe it's the same recipe.  Maybe it wasn't - maybe I missed something.

 

Marcia- yes, I saw your name on some of the recipes in Mr. Britt's book.  And thank you for the additional recipes; I will *definitely* try the "faux" celadon, (yum).  Very pretty.  I will also look up Mr. Bailey's glaze book.

 

Denice - thank you!

 

Min- *sigh* - the cup is beautiful.  Thanks for the nudges; I (foolishly) thought I could skip the test tiles.  I finally see a very good reason to use them.

 

Joseph - thank you for the commiseration, lol.  I think that's some sound advice.

Guess what I will be doing tomorrow?

[neilestrick]

Definitely check your kiln by placing cones throughout. A Skutt 1227 is a big kiln and with only one thermocouple you could have a huge difference in temperatures around the kiln.

 

Keep testing!

[MatthewV]

Re: spec grav - does every glaze have it's own specific gravity or do I just have to figure it out as I go?

 

Yes, but what this number is will depend on how you apply the glaze, how you bisque fire your work, and how thick you make your work. So there isn't a magic number I can give you (partly because...errr... I guess with a "calibrated stir")

 

Here are the more helpful details:
https://digitalfire.com/4sight/glossary/glossary_specific_gravity.html

[High Bridge Pottery]

2 out of 7 working sounds good for a first attempt   Depending how deep you want to go the glaze hole never ends.

 

Assads Opalescent has a lot of talc and kaolin in which will be making it crawl, you could try reducing both a little and it could help things. The Karakowski is probably more down to your firing curve, under the picture in john britt's book it says cone6 electric slow cooled(just realised the picture is about completely different glazes) . 

 

Without the other recipes I am not sure, the Tahitian probably has a bit of clay in too making it look thick before being fired.

[Sheryl Leigh]

Thanks again, Matthew.  Looks like I have the tools to measure the spec grav, yay!

 

Thanks, Joel - 2 outta 7?? Yikes!
 

I believe Mr. Britt also gives a slow-cool program in his book. I'm not sure that I'll always need it - seems like an ambient temp of 110F/43C will keep it fairly hot for a long, long time.  Okay, that's summer, but still...

 

The Tahitian is (rounding off):

 

Gerstley   53

Silica        26

EPK          21

Zircopax   10

 

with Rutile, copper and cobalt carb.  Would you consider that a lot of clay?

 

Spent some time this morning making test tiles.  Here we go....!

[neilestrick]

Thanks again, Matthew.  Looks like I have the tools to measure the spec grav, yay!

 

Thanks, Joel - 2 outta 7?? Yikes!

 

I believe Mr. Britt also gives a slow-cool program in his book. I'm not sure that I'll always need it - seems like an ambient temp of 110F/43C will keep it fairly hot for a long, long time.  Okay, that's summer, but still...

 

The Tahitian is (rounding off):

 

Gerstley   53

Silica        26

EPK          21

Zircopax   10

 

with Rutile, copper and cobalt carb.  Would you consider that a lot of clay?

 

Spent some time this morning making test tiles.  Here we go....!

 

This is not a good glaze. It's one of those old school "I love Gerstley" glazes formulated without looking at limit formulas. It will likely melt okay, but it's not a well balanced durable glaze. The calcium and boron (and almost magnesium) are off the charts. And with that much Gerstley it's prone to all sorts of issues. Stick to glazes that have a least 2 or 3 flux ingredients.

[Sheryl Leigh]

Thanks, Neil.